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St, Clair Gibson Alan. "Fatigue, aging and the neuromuscular system." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/3205.
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Bibliography: p. 400-445.<br>The aim of this thesis was to investigate the relationship between chronic exercise activity, aging, the neuromuscular system and the symptom of fatigue in a series of studies. The hypothesis of the thesis was that in contrast to the accepted dogma that exercise is beneficial to an individual, increasing longevity and improving quality of life, excessive or chronic exercise activity may accelerate the aging process, lead to neuromuscular damage, and cause the development of pathological symptoms or levels of fatigue.
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Taylor, Kristie-Lee. "Monitoring neuromuscular fatigue in high performance athletes." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2012. https://ro.ecu.edu.au/theses/581.
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With improving professionalism of sports around the world, the volume and frequency of training required for competitive performances at the elite level has increased concurrently. With this amplification in training load comes an increased need to closely monitor the associated fatigue responses, since maximising the adaptive response to training is also reliant on avoiding the negative consequences of excessive fatigue. The rationale for the experimental chapters in this thesis was established after considering survey responses regarding current best practice for monitoring fatigue in high performance sporting environments (Chapter 3). On the basis of the results, vertical jump assessments were selected for further investigation regarding their utility in determining neuromuscular fatigue responses. Outcomes from the subsequent series of studies aimed to provide practitioners working in high performance sport with guidelines for using vertical jumps to monitor athletic fatigue.
The results from Chapter 4 indicate using the mean value of at least six jumps enhances the ability to detect small but practically important changes in performance from week to week. This study also highlighted large differences (4-6%) in morning and afternoon performance, indicating that the time of day performance is assessed needs to be accounted for when monitoring changes in jump performance. Chapter 5 explored the theory that the time of day effect observed in Chapter 4 can be explained by internal temperature differences. This theory was supported by demonstrating that an extended warm-up period can negate differences in jump performance in the morning and the afternoon. Researchers who are unable to standardise the time of day that assessment occurs are able, therefore, to control for performance differences by manipulating the warm-up protocols.
The third study examined changes in vertical jump performance over a three month training period and produced several novel outcomes. A major finding was that unloaded jumps were more sensitive to neuromuscular fatigue during intensive training than loaded jumps (Chapter 6). Furthermore, this set of results showed that all subjects changed their jump technique via a reduction in the amplitude of the countermovement when they were highly fatigued. Using the same data, an analysis was performed to quantify individual differences in within-subject variation (Chapter 7) during normal and intensive training. These results provided the first indication that within-subject variability in vertical jump performance is substantially different between individuals and between different training phases, an important consideration for interpreting the practical importance of performance changes.
In Chapter 8 the relationship between vertical jump performance and electrically elicited force of the knee extensors was examined to better understand the mechanism(s) of changes in jump performance associated with neuromuscular fatigue during intensive overload training. The results showed that the fatigue assessed by vertical jump performance was likely not only peripheral in origin as previously suggested by other authors. Further research is required to further understand the mechanisms of reduced performance during overload training, although the preliminary evidence presented implicates central mechanisms. To conclude the thesis, the findings presented in the experimental chapters are summarised, with a series of practical recommendations for using vertical jumps to monitor athletic fatigue presented.
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Lin, Zengyuan. "Neuromuscular fatigue following a singles badminton match." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2014. https://ro.ecu.edu.au/theses/1279.
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A typical badminton singles match involves numerous intense and high impact movements. Lunges were accounted for approximately 15% of overall movements and were believed to presumably induce significant muscle damage following a match. However, no previous study has investigated changes in knee extensor muscle function after a badminton match.The present study investigated changes in knee extensor neuromuscular function and muscle soreness after a simulated 1-h badminton singles match in relation to the number of lunges performed in the match.
Ten state-level male badminton players were recruited (n=10), with each player played a total of eight simulated 1-h matches under the International Badminton World Federation rules. However, each participant was required to play against the same opponent twice and only one participant was fitted with the equipment at any one session, thus the total number of matches analysed was 40. The number of lunges performed by each player in a game was obtained from video analysis. Heart rate (HR) and core body temperature were recorded during the matches, and blood lactate (BL) was measured before and immediately post match. Both femoral nerve and muscle electrical stimulations were used in the present study. Maximal voluntary isometric contraction (MVC) torque of the knee extensors and flexors, voluntary activation during the knee extension MVC (VA), torque generated by a doublet (DT), and 20 Hz (T20) and 80 Hz stimulation (T80) and the ratio (T20/T80) for the knee extensors, and muscle soreness of knee extensor muscles by a 100-mm visual analog scale (VAS) were measured before, immediately (8 - 10 min post-match), 1-h and 24-h after a match. Pearson product-moment correlations were computed to examine relationships between variables using ANOVA.Average (± SD) match HR was 162.0 ± 11.0 bpm, post-match BL was 7.2 ± 1.3 mM.L-1, and 194 ± 18 lunges were performed per match per player. Core body temperature increased from 36.5 ± 0.5 oC to 39.4 ± 0.5 oC immediately post match. Knee extension MVC torque was lower than baseline (278.4 ± 50.8 Nm) at immediately (-11%) and 1 h (-14%) post match (P
Moderate muscle soreness developed after 1-h simulated badminton matches, but muscle function returned to baseline by 24 hour post match, indicating moderate muscle fibre damage. Since VA was decreased without changes in T20/T80, and knee flexion MVC torque also showed similar changes to those of knee extension MVC torque that was thought to be affected by lunges, the decrease in MVC torque appeared to be associated with central rather than peripheral fatigue or muscle damage. With moderate muscle soreness developing after 1-h simulated badminton matches and muscle function returning to baseline by 24 hour post-game, suggesting minimal muscle fibre damage. It was concluded that both central and peripheral factors contributed to alterations in neuromuscular fatigue and that muscle damage was moderate after the singles matches in which the game intensity and physiological characteristics were close to those in competitive tournaments.
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Alahmari, Sami Khaloufah M. "Muscle force production and neuromuscular fatigue responses to neuromuscular electrical stimulation and tendon vibration." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/236174/1/Sami_Alahmari_Thesis.pdf.
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Neuromuscular electrical stimulation is an intervention that produces artificial muscle contractions and is used to rehabilitate people with motor impairments. However, a typical problem is the occurrence of rapid fatigue, which limits the training stimulus. This thesis investigated whether the addition of tendon vibration and concurrent activation of upper limb muscles could minimise fatigue and maximise torque produced by the calf muscles during neuromuscular electrical stimulation. The experiments in this thesis showed that superimposition of tendon vibration can increase the amount of torque produced by calf muscles, and that the addition of sustained handgrip contraction could further increase this torque.
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Lloyd, Alex. "Neuromuscular fatigue, muscle temperature and hypoxia : an integrative approach." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21766.
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Real world exposures to physiologically and/or psychologically stressful environments are often multifactorial. For example, high-altitude typically combines exposure to hypobaric hypoxia, solar radiation and cold ambient temperatures, while sea level thermal stress is often combined with supplementary or transient stressors such as rain, solar radiation and wind. In such complex environments, the effect of one stressor on performance may be subject to change, simply due to the presence of another independent stressor. Such differential influences can occur in three basic forms; additive, antagonistic and synergistic, each term defining a fundamental concept of inter-parameter interactions. As well as the natural occurrence of stressors in combination, understanding interactions is fundamental to experimentally modelling how multiple physiological strains integrate in their influence on or regulation of - exercise intensity. In this thesis the current literature on neuromuscular fatigue and the influence of thermal and hypoxic stress is reviewed (Chapter 1). This is followed by an outline of the methodological developments used in the subsequent experiments (Chapter 2). In the first experimental study (Chapter 3) a novel approach was adopted to investigate the combined effect of muscle cooling and hypoxia on neuromuscular fatigue in humans. The results showed that the neuromuscular system s maximal force generating capacity declined by 8.1 and 13.9% during independent cold and hypoxic stress compared to control. Force generation decreased by 21.4% during combined hypoxic-cold compared to control, closely matching the additive value of hypoxia and cold individually (22%). This was also reflected in the measurement of mechanical fatigue (electromechanical ratio), demonstrating an additive response during combined hypoxic-cold. From this study, it was concluded that when moderate hypoxia and cold environmental temperatures are combined during low intensity exercise, the level of fatigue increases additively with no interaction between these stressors. Before conducting a more complex investigation on combined stressors, a better understanding of the role of muscle temperature on central fatigue - i.e. voluntary muscle activation via the afferent signalling pathways was sought. The focus of Chapter 4 was to quantify the relationship between muscle temperature and voluntary muscle activation (central fatigue) across a wide range of temperatures. The primary finding was that different muscle temperatures can induce significant changes in voluntary activation (0.5% reduction per-degree-centigrade increase in muscle temperature) when neural drive is sustained for a prolonged effort (e.g. 120-s); however this effect is not exhibited during efforts that are brief in duration (e.g. 3-s). To further explore this finding, Chapter 5 investigated the effect of metaboreceptive feedback at two different muscle temperatures, using post-exercise muscle ischemia, on voluntary activation of a remote muscle group. The results showed that at the same perceived mental effort, peripheral limb discomfort was significantly higher with increasing muscle temperature (2% increase per-degree-centigrade increase). However any influence of increased muscle temperature on leg muscle metaboreceptive feedback did not appear to inhibit voluntary muscle activation - i.e. central control - of a remote muscle group, as represented by an equal force output and voluntary activation in the thermoneutral, contralateral leg. In Chapter 6, the psycho-sensory effects of changes in muscle temperature on central fatigue during dynamic exercise were investigated. During sustained dynamic exercise, fatigue development appeared to occur at a faster rate in hot muscle (4% increase per-degree-centigrade increase) leading to a nullification of the beneficial effects of increased muscle temperature on peak power output after a period of ~60-s maximal exercise. In support of previous studies using isometric exercise (Chapter 4 and 6), participants reported significantly higher muscular pain and discomfort in hot muscle compared to cooler muscle during dynamic exercise (2 and 1% increase per-degree-centigrade increase respectively), however this did not result in a lower power output. From Chapters 4, 5 and 6 it was concluded that in addition to faster rates of metabolite accumulation due to cardiovascular strain, it is possible that a direct sensitisation of the metaboreceptive group III and IV muscle afferents occurs in warmer muscle. This likely contributes to the reduction in voluntary muscle activation during exercise in the heat, while it may attenuate central fatigue in the cold. It was also interpreted that muscle afferents may have a similar signalling role to cutaneous sensory afferents; the latter of which are recognised for their role in providing thermal feedback to the cognitive-behavioural centres of the brain and aiding exercise regulation under thermal stress. The impact of body core and active muscle temperature on voluntary muscle activation represented a similar ratio (5 to 1 respectively) to the temperature manipulated (single leg) to non-temperature manipulated mass (rest of body) in Chapters 4, 5 and 6. This indicates that voluntary muscle activation may also be regulated based on a central meta-representation of total body heat content i.e. the summed firing rates of all activated thermoreceptors in the brain, skin, muscle, viscera and spine. Building on the initial findings of Chapter 3, Chapter 7 investigated the causative factors behind the expression of different interaction types during exposure to multi-stressor environments. This was achieved by studying the interaction between thermal stress and hypoxia on the rate of peripheral and central fatigue development during a high intensity bout of knee extension exercise to exhaustion. The results showed that during combined exposure to moderate hypoxia and mild cold, the reductions in time to exhaustion were additive of the relative effects of hypoxia and cold independently. This differs from the findings in Chapter 3, in which fatigue was additive of the absolute effects of cold and hypoxia. In contrast, combining moderate hypoxia with severe heat stress resulted in a significant antagonistic interaction on both the absolute and relative reductions in time to exhaustion i.e. the combined effect being significantly less than the sum of the individual effects. Based on the results in Chapter 7, a quantitative paradigm for understanding of systematic integration of multifactorial stressors was proposed. This is, that the interaction type between stressors is influenced by the impact magnitude of the individual stressors effect on exercise capacity, whereby the greater the stressors impact, the greater the probability that one stressor will be cancelled out by the other. This is the first study to experimentally model the overarching principles characterising the presence of simultaneous physiological strains, suggesting multifactorial integration be subject to the worst strain takes precedence when the individual strains are severe.
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Yang, Qi. "BIO-SIGNAL ANALYSIS IN FATIGUE AND CANCER RELATED FATIGUE: WEAKENING of CORTICOMUSCULAR FUNCTIONAL COUPLING." Cleveland, Ohio : Cleveland State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1213888265.
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Thesis (D.Eng.)--Cleveland State University, 2008.<br>Abstract. Title from PDF t.p. (viewed on Oct. 8, 2008). Includes bibliographical references (p. 91-99). Available online via the OhioLINK ETD Center. Also available in print.
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Reed, Georgina. "The effect of neuromuscular training on fatigue resistance in female footballers." Thesis, University of Gloucestershire, 2017. http://eprints.glos.ac.uk/5285/.
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ACL injury is predominant in female footballers largely due to a combination of kinetic and neuromuscular risk factors. The majority of ACL injuries in football occur during an unanticipated cutting manoeuvre, and the risk of this injury is heightened during the final 30 minutes of each half of match-play. Due to an increased injury incidence towards the end of match-play, it is possible that fatigue might serve as a risk factor for ACL injury. However, there currently exists limited research examining the effects of fatigue on a variety of kinetic and electromyographic variables in female footballers during an unanticipated cutting manoeuvre. Neuromuscular training programmes have been utilised in injury prevention studies and proven effective in reducing injury incidence by improving certain kinetic and neuromuscular ACL injury risk factors. The overall aim of this thesis is to examine the effectiveness of neuromuscular training on the fatigue resistance of ACL injury risk factors in female footballers. Study one of this thesis examined the reliability of a combination of kinetic and electromyographic measures in female footballers performing an unanticipated cutting manoeuvre. There were no significant differences in mean values and large to nearly perfect correlations (ICC = 0.49 - 0.96) for all kinetic variables. The majority of kinetic variables displayed a CV of less than 10%, with the exception of loading rates and time to peak force (CV% = 17.33 - 24.51). In comparison to previous research, electromyographic variables displayed a greater range of typical error (CV% = 17.6 - 129.2); however, the majority of electromyographic variables displayed a large, very large or nearly perfect correlation (ICC = 0.26 – 0.91) and no significant differences in the mean score. In line with previous research, standards of reliability, and anticipated changes in response to acute fatigue, all kinetic and electromyographic variables were deemed acceptable to use in subsequent studies. Kinetic variables showed better reliability than electromyographic variables, which was to be expected due to electromyographic measures being a physiological measure. Previous research has established that 16 - 18 year old female footballers are at highest risk of ACL injury, and it is most commonly caused during performance of an unanticipated cutting manoeuvre. It has also been established that the majority of injuries in female football are sustained in the last 30 minutes of each half when fatigue is present. Therefore, acute fatigue appears to be an influential risk factor for ACL injury. Study two of this thesis examined the effects of acute fatigue on the electromyographic and kinetic ACL injury risk factors in 16 - 18 year old female footballers, when performing an unanticipated cutting manoeuvre. A modified SAFT90 protocol was used to mimic football match-play. Data showed that during the unanticipated cutting manoeuvre following the SAFT90, participants produced greater GRF (vGRF; possibly, apGRF very likely), lower GCT (very likely), increased background hamstring activation (0 - 30 ms; very likely) and increased short-latency feedback activation of the hamstrings (31 - 60 ms; likely and possibly). Results suggested that following a simulated match-play protocol, female footballers experienced greater force absorption while utilising a safer muscle recruitment strategy. Therefore, injury prevention training should seek to improve a player’s aility to tolerate ground reaction forces when experiencing acute fatigue, with a large emphasis on enhancing neuromuscular control within the hamstrings muscle group.
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Cormack, Stuart J. "Neuromuscular fatigue and endocrine responses in elite Australian rules football players." Connect to thesis, 2008. http://portal.ecu.edu.au/adt-public/adt-ECU2008.0010.html.
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BERETTA-PICCOLI, MATTEO CARLOFELICE. "EVALUATION OF NEUROMUSCULAR FATIGUE THROUGH INNOVATIVE SURFACE EMG PARAMETERS IN HUMANS." Doctoral thesis, Università degli studi di Pavia, 2020. http://hdl.handle.net/11571/1371980.
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The surface electromyogram (EMG) undergoes several changes during an isometric fatiguing muscle contraction. Amplitude and spectral parameters, as well as muscle fiber conduction velocity and fractal dimension of the surface EMG signal, may be used as indirect fatigability indices to monitor these changes. The aims of this thesis were to determine whether surface EMG is a reliable tool for estimating conduction velocity, through a systematic review of the literature; to determine the relationship between muscle force and the selected fatigability indices; and to study the behavior of the fatigability indices in patients with facioscapulohumeral muscular dystrophy (FSHD) during a fatiguing task, with respect to healthy controls. It was hypothesized that the fractal dimension was not related to the intensity of muscle contraction, and that FSHD patients would have shown significant differences in the considered fatigability indices. In the first study (p. 32) high reliability was reported in eight studies and was, in general, associated with using the initial or mean conduction velocity value, using several electrodes (3 to 8), ensuring appropriate electrode positioning, and evaluating muscles with fibers that run parallel to the skin. It was next demonstrated in the second study (p. 52), that the values of fractal dimension and mean frequency of the power spectrum increased with force unless a plateau was reached at 30% maximal voluntary contraction. Finally, the third study (p. 61) showed that FSHD patients presented significantly less steeper slopes of mean frequency of the power spectrum, conduction velocity and fractal dimension, compared to the controls. The results of this thesis demonstrated firstly, that sEMG is suitable for use when investigating conduction velocity, which is sensible to peripheral aspects affecting performance fatigability; secondly, the use of fractal dimension, as index of central factors affecting performance fatigability, may be considered above a certain level of force, regardless of muscle contraction intensity; and lastly, that impaired neuromuscular function caused patients with FSHD to exert a smaller force, yield a longer endurance time and experience lower levels of performance fatigability compared to healthy participants. In conclusion, the use of the fractal dimension of the sEMG signal to infer central aspects of performance fatigability should be promoted; in particular, in those muscles were motor unit decomposition techniques are limited by anatomical constraints.
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Castronovo, Anna Margherita <1984>. "Techniques and Methods for a multi-scale analysis of neuromuscular fatigue." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6274/7/Castronovo_AnnaMargherita_tesi.pdf.
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This thesis proposes an integrated holistic approach to the study of neuromuscular fatigue in order to encompass all the causes and all the consequences underlying the phenomenon. Starting from the metabolic processes occurring at the cellular level, the reader is guided toward the physiological changes at the motorneuron and motor unit level and from this to the more general biomechanical alterations. In Chapter 1 a list of the various definitions for fatigue spanning several contexts has been reported. In Chapter 2, the electrophysiological changes in terms of motor unit behavior and descending neural drive to the muscle have been studied extensively as well as the biomechanical adaptations induced. In Chapter 3 a study based on the observation of temporal features extracted from sEMG signals has been reported leading to the need of a more robust and reliable indicator during fatiguing tasks. Therefore, in Chapter 4, a novel bi-dimensional parameter is proposed. The study on sEMG-based indicators opened a scenario also on neurophysiological mechanisms underlying fatigue. For this purpose, in Chapter 5, a protocol designed for the analysis of motor unit-related parameters during prolonged fatiguing contractions is presented. In particular, two methodologies have been applied to multichannel sEMG recordings of isometric contractions of the Tibialis Anterior muscle: the state-of-the-art technique for sEMG decomposition and a coherence analysis on MU spike trains. The importance of a multi-scale approach has been finally highlighted in the context of the evaluation of cycling performance, where fatigue is one of the limiting factors. In particular, the last chapter of this thesis can be considered as a paradigm: physiological, metabolic, environmental, psychological and biomechanical factors influence the performance of a cyclist and only when all of these are kept together in a novel integrative way it is possible to derive a clear model and make correct assessments.
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Castronovo, Anna Margherita <1984>. "Techniques and Methods for a multi-scale analysis of neuromuscular fatigue." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6274/.
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This thesis proposes an integrated holistic approach to the study of neuromuscular fatigue in order to encompass all the causes and all the consequences underlying the phenomenon. Starting from the metabolic processes occurring at the cellular level, the reader is guided toward the physiological changes at the motorneuron and motor unit level and from this to the more general biomechanical alterations. In Chapter 1 a list of the various definitions for fatigue spanning several contexts has been reported. In Chapter 2, the electrophysiological changes in terms of motor unit behavior and descending neural drive to the muscle have been studied extensively as well as the biomechanical adaptations induced. In Chapter 3 a study based on the observation of temporal features extracted from sEMG signals has been reported leading to the need of a more robust and reliable indicator during fatiguing tasks. Therefore, in Chapter 4, a novel bi-dimensional parameter is proposed. The study on sEMG-based indicators opened a scenario also on neurophysiological mechanisms underlying fatigue. For this purpose, in Chapter 5, a protocol designed for the analysis of motor unit-related parameters during prolonged fatiguing contractions is presented. In particular, two methodologies have been applied to multichannel sEMG recordings of isometric contractions of the Tibialis Anterior muscle: the state-of-the-art technique for sEMG decomposition and a coherence analysis on MU spike trains. The importance of a multi-scale approach has been finally highlighted in the context of the evaluation of cycling performance, where fatigue is one of the limiting factors. In particular, the last chapter of this thesis can be considered as a paradigm: physiological, metabolic, environmental, psychological and biomechanical factors influence the performance of a cyclist and only when all of these are kept together in a novel integrative way it is possible to derive a clear model and make correct assessments.
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Overton, Amanda Julie. "Neuromuscular Fatigue and Biomechanical Alterations during High-Intensity, Constant-Load Cycling." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/612.
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Neuromuscular fatigue is an inevitable process at play during prolonged exercise, and may be caused by multiple alterations within the central nervous system and peripheral musculature. As fatigue develops, the neuromuscular system must adapt to these changes by making compensatory movement pattern adjustments so as to use motor pathways that are less fatigued in an effort to maintain task performance; motor variability is thus increased. The primary purpose of the four studies contained within this doctoral thesis was to detail the progression of exercise-induced neuromuscular fatigue, and to improve our understanding of the muscle activation and joint kinematic alterations that occur as fatigue accumulates. Within this context, cycling was used as the exercise model, and the relationship between physiological and biomechanical aspects of high-intensity, moderate duration (<10 >min) cycling were specifically examined. The first two studies of this thesis were aimed at understanding the progression of neuromuscular fatigue as well as the associated motor control and biomechanical (i.e. muscle activation and kinematic) changes that occur during exhaustive cycling. Specifically, the time course and relative contributions of central and peripheral fatigue mechanisms, and the associated changes in muscle activation and both lower (i.e. hip, knee and ankle joint) and upper (i.e. trunk) limb kinematics were examined during a high-intensity cycling time to exhaustion (TTE) test. This was performed at 90% maximal aerobic power (Pmax) with nine well-trained cyclists. Temporal relationships between joint kinematics and changes in markers of central and peripheral fatigue were also examined. Peripheral fatigue (i.e. impaired contractile function: reduced peak twitch torque, −39.9%; twitch contraction time, −10.7%; and the average rates of twitch torque development −34.7% and relaxation −36.7% at task failure i.e., T100) developed early in the exercise bout from 60% of the time to task failure (p < 0.05). However, a central facilitation, measured as an increase in peak vastus medialis (38.9%) and gluteus maximus electromyogram (87.2%) amplitudes at T100, rather than central fatigue, occurred towards the end of the exercise task (p < 0.05). Thus, neuromuscular fatigue development was associated with an increase in the magnitude of lower limb muscle activity, which may have represented an attempt to increase muscle force to maintain the required power output of the cycling task. Increases in trunk flexion were observed from 60% of the time to task failure (p < 0.05), and were therefore notable at or after the point of significant peripheral fatigue. Conversely, increases in trunk medio-lateral sway (lateral flexion), hip abduction/adduction and knee valgus/varus were observed only from 80% of the time to task failure (p < 0.05), which paralleled the increase in central motor drive. The results of this study therefore indicate that significant trunk kinematic changes in the sagittal plane occurred at or after the point of significant peripheral fatigue development, whereas, significant changes at the trunk, hip and knee joints in the coronal plane occurred later in the exercise task and paralleled the facilitation of central motor drive during the cycling task. In the third study, the effects of real-time, kinematic feedback provision for trunk flexion (TTETflex), trunk medio-lateral sway (TTETsway) and hip abduction/adduction (TTEHabd/add) during a high-intensity TTE cycling test (90% Pmax) in nine well-trained cyclists were examined. The times taken to reach task failure were compared to a TTE test completed with no feedback. The times taken to reach task failure were not significantly different when provided with trunk flexion (TTETflex) and hip abduction/adduction (TTEHabd/add) feedback compared to the non-feedback condition (p > 0.05). There was, however, a significant decrease in the time to task failure during the TTETsway test (p < 0.05). Not all participants could maintain trunk and/or hip movement within a set movement pattern criteria; and three participants were therefore excluded from the kinematic analyses for both the TTETflex and TTETsway tests (n = 6) as were two participants from the TTEHabd/add test (n = 7). For participants who correctly used the kinematic feedback, no differences in the times taken to reach failure were observed in between the feedback (TTETflex, TTETsway and TTEHabd/add) and nonfeedback test conditions (p > 0.05). Despite being given feedback, changes in joint kinematics were similar across all test conditions; significant alterations were observed at the trunk and knee joints in the sagittal plane and at the hip and knee joints in the coronal plane (p < 0.05). Given trunk flexion feedback (TTETflex), significant increases in left hip flexion and trunk medio-lateral sway ROM were observed (p < 0.05), whereas given trunk medio-lateral sway feedback (TTETsway), increases in right hip flexion ROM also occurred (p < 0.05). These results indicate that, regardless of whether or not well-trained cyclists are able to control the level of kinematic variability when fatigued, acute exposure to real-time kinematic feedback to limit trunk or hip movement during high-intensity cycling may influence cycling kinematics (i.e. technique) and, in some cases (e.g. trunk medio-lateral sway), may reduce performance. The final study examined the relationship between joint kinematics, measured in non-fatigued and fatigued high-intensity cycling, and the cyclists’ physiological profiles (i.e., physiological attributes indicative of successful cycling ability, including both maximal oxygen consumption and peak power output relative to body mass, maximal heart rate, both power output and heart rate at the first and second ventilatory thresholds and cycling economy at 100 W) and the time taken to reach task failure. Submaximal physiological attributes were correlated with hip (abduction/adduction angle and ROM), knee (flexion angle) and ankle (flexion ROM) kinematics measured in a non-fatigued state at the start of the trial (r > 0.40; p < 0.05). However, both physiological attributes associated with maximal exercise capacity and cycling economy were correlated with trunk (flexion angle) and ankle (flexion angle and ROM) kinematics measured in a fatigued state at the end of the test (r > 0.40; p < 0.05). Trunk flexion and medio-lateral sway ROM in a non-fatigued state, and trunk flexion angle in a fatigued state, were associated with the time to task failure (r > 0.50; p < 0.05). Thus, the degree of trunk flexion and medio-lateral sway may be important kinematic variables that are indicative of cycling performance. These findings reveal an interdependence between cycling kinematics and both the physiological attributes indicative of successful cycling performance and the time taken to reach task failure during high-intensity, constant-load cycling. In conclusion, the findings presented in this thesis indicate that the temporal patterns of central and peripheral neuromuscular fatigue differ (Study 1; Chapter 3). Task failure during high intensity cycling appears to be associated with the development of peripheral fatigue despite the presence of an increase in central motor drive. Subsequent to the development of neuromuscular fatigue, muscle activation and joint kinematic alterations can be observed, which may represent compensatory mechanisms employed by the neuromuscular system to continue task performance (Studies 1 and 2; Chapters 3 and 4). Joint kinematic alterations in the sagittal plane were associated with the development of peripheral fatigue whereas coronal plane adjustments occurred in parallel with central facilitation, and/or when a more substantial level of peripheral fatigue accumulated. Such compensatory kinematic strategies are also associated with an athlete’s physiological attributes and their cycling performance (i.e., time to task failure) (Study 4; Chapter 6). Importantly, imposing specific joint kinematic restrictions (trunk flexion, trunk medio-lateral sway and hip abduction/adduction) during exhaustive cycling, influenced cycling kinematics (i.e. technique) and, in some cases (e.g. trunk medio-lateral sway), reduced the time taken to reach task failure for well-trained cyclists (Study 3; Chapter 5). Such findings enhance our understanding of how the neuromuscular system copes with fatigue development, and should assist coaches and/or occupational health practitioners to better understand the fatigue process and neuromuscular strategies utilised during exercise tasks with similar characteristics to that used in the current studies.
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Cormack, Stuart J. "Neuromuscular fatigue and endocrine responses in elite Australian Rules football players." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2008. https://ro.ecu.edu.au/theses/19.
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The first purpose of this research was to establish the reliability of numerous measures obtained from a single and short duration repeated countermovement jump (CMJ) utilising a portable forceplate (Experimental Studies 1 and 2). Secondly, the response of reliable CMJ variables and T, C and T:C to a single elite level ARF match was assessed to identify the pattern of response and highlight those measures with the greatest potential for usefulness as monitoring tools across longer periods (Experimental Study 3). Finally, those variables identified as most valuable in Experimental Study 3 in addition to T, C and T:C; were measured throughout a season of elite ARF competition in order to examine the manner of their response and assess the magnitude of change in these variables in relation to performance and training and competition loads (Experimental Study 4).
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Piponnier, Enzo. "Etude des différences de fatigue neuromusculaire entre enfants et adultes en fonction du groupe musculaire, de la longueur musculaire et du profil métabolique." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAS013/document.
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Les objectifs de ce travail de thèse étaient d’évaluer les effets des différences (i) de niveau de force, en utilisant différents groupes et longueurs musculaires, et (ii) de profil métabolique entre enfants pré-pubères et adultes sur les différences de développement et d’origine de la fatigue neuromusculaire, ainsi que (iii) d’accroître nos connaissances sur les mécanismes de la fatigue neuromusculaire chez l’enfant pré-pubère. Les résultats de ce travail montrent que les différences de niveau de force pourraient être un facteur expliquant les différences de développement et d’origine de la fatigue neuromusculaire entre enfants et adultes. Toutefois, ce facteur n’est pas suffisant pour expliquer toutes les différences de fatigue entre ces deux populations. En effet, nos résultats soulignent aussi que les différences de profil métabolique pourraient être impliquées de façon importante dans les différences de développement et d’origine de la fatigue neuromusculaire entre enfants et adultes. Par ailleurs, les résultats de nos études rapportent que les enfants présentent généralement une fatigue périphérique plus faible par rapport aux adultes au profit d’une fatigue centrale plus importante suite à un protocole de fatigue maximal intermittent. Cette moindre fatigue périphérique est associée à une moindre altération des propriétés contractiles et du couplage excitation-contraction, et à une meilleure adaptation de l’oxygénation musculaire chez l’enfant pré-pubère. Nos résultats semblent suggérer que la fatigue spinale ne permettrait pas d’expliquer les différences de fatigue centrale entre enfants et adultes et donc que la fatigue centrale plus importante des enfants pourrait être attribuée à une fatigue supra-spinale plus élevée<br>The aims of this PhD thesis were to evaluate the effects of differences of (i) force level, throughout different muscle groups and muscle lengths, and (ii) metabolic profile on the differences of development and etiology of the neuromuscular fatigue between prepubertal children and adults, as well as (iii) to improve our knowledge of the mechanisms of neuromuscular fatigue in children. The results of this PhD thesis showed that force level differences could be a factor underpinning the differences in the development and etiology of neuromuscular fatigue between children and adults. However, this factor cannot fully account for differences in fatigue between both populations. Indeed, our results also highlighted that metabolic profile differences could explain the difference of development and etiology of neuromuscular fatigue between children and adults. Additionally, the results of this thesis showed that children exhibit lower peripheral fatigue and greater central fatigue than adults after an intermittent maximal exercise. This lower peripheral fatigue was associated with a lower alteration of the contractile properties and excitation-contraction coupling, and a better adaptation of the muscle oxygenation in prepubertal children. Our results suggest that spinal fatigue could not explained the differences in central fatigue between children and adults, and that the greater central fatigue in children could be attributed to a greater supra-spinal fatigue
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Kennedy, Ashley C. "Impact of Neuromuscular Fatigue on the Postural Response to Externally Initiated, Predictable Postural Perturbations." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24369.
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Neuromuscular fatigue, even that caused by light submaximal exercise, impairs motor performance and alters motor planning. This impairment is evident in muscle reaction time, force production capacity and joint position sense as well as in more complex tasks such as postural stability. When an individual is fatigued their postural sway increases and they are less able to recover from unexpected postural perturbations. Although a large number of work-related falls are caused by fatigue every year, the mechanisms behind the instability are not well understood. Since postural control does not require a large amount of muscular strength it is unclear whether the post-fatigue changes in posture are due to impairment within the muscle fibers or are a central modification of the motor plan used to execute the movement task.
In order to better understand neuromuscular fatigue researchers have labeled fatigue occurring within the muscles ‘peripheral fatigue’ and that occurring within the central nervous system ‘central fatigue’. At the onset of a muscular contraction peripheral and central fatigue develop simultaneously, making it difficult to clearly articulate the role that they each play in the decreased motor performance found post-fatigue. Techniques such as transcranial magnetic and electrical nerve stimulation quantify the contribution of central fatigue to the decreased maximal force production but the impact on motor planning is still not well understood. Therefore, the primary aim of this doctoral dissertation was to isolate central fatigue from peripheral muscle fatigue and to compare the influence that it may have on dynamic postural control to the changes caused by general fatigue of the local postural muscles.
This overarching research goal was accomplished through five separate studies. The first study in this dissertation determined that at least seven postural trials needed to be performed to ensure that the participants had fully adapted to the postural task before the fatigue protocol was implemented. Experiment 2 characterized the fatigue produced by bilateral, isometric ankle muscle contractions and examined the recovery of the central and peripheral changes throughout a ten-minute post-fatigue recovery period. The results demonstrated that the alternating maximal ankle plantar and dorsiflexor contractions created central and peripheral fatigue. Central fatigue recovered within the first two minutes post-fatigue while peripheral fatigue lasted throughout the ten-minute post-fatigue period. Experiment 3 analyzed the impact of this ankle muscle fatigue protocol on the postural response to a continual, externally driven, sinusoidal oscillation of the support platform. In this study the fatigued participants were able to stabilize their center of mass displacement using two different anticipatory postural responses to the backwards perturbation whereas all of the participants used the same anticipatory response to the forwards perturbation. All three postural responses became progressively more conservative throughout the ten-minute post-fatigue period, despite the rapid recovery of the ankle force production capacity.
The final two studies characterized the fatigue produced during a continuous, isometric forearm contraction and assessed the impact on ankle motor performance (Experiment 4) and on postural control (Experiment 5). Peripheral fatigue created in the forearm muscles during this contraction remained throughout the post-fatigue testing session. Central fatigue and a decreased maximal force production capacity were quantified in both the forearm and ankle plantarflexor muscles immediately after the forearm contraction, indicating that central fatigue created during the forearm exercise crossed over to the distal and unrelated ankle plantarflexor muscles. The influence of the central fatigue created during the forearm contraction affected the anticipatory postural response in a similar way to the fatigue created by the ankle fatigue protocol. The post-fatigue modification of the postural response dissipated as the central fatigue recovered. Taken together, these five studies extend the current understanding of how exercise induced neuromuscular fatigue modifies the central nervous system’s control of complex motor tasks.
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Vaughan, Jeremiah A. "Neuromuscular Function and Fatigue and Metabolic Responses while Cycling in the Heat." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1542212848069694.
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Cardwell, Kathryn. "The assessment of movement demands and neuromuscular fatigue in female softball players." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2501.
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Softball has experienced an increase in worldwide popularity over the last 15 years, and it is expected to rise following the reinstatement of softball as an Olympic sport in 2021. Previous softball research has primarily focused on the biomechanical characteristics of its athletes. However, there is a current lack of research concerning the movement demands occurring in gameplay and the development of neuromuscular fatigue in softball players during sportspecific movements, training sessions, or in competition play. Prior research has demonstrated that a majority of power generated during a bat swing or overhand throw comes from the lower body, with the hip musculature playing an essential role in stabilisation and kinetic energy transmission. Understanding the development of neuromuscular fatigue, particularly in the hip musculature of softball athletes, will allow coaches and sport scientists to optimise training sessions, athlete monitoring techniques, and recovery methods. Accordingly, the overall aims of this thesis were to 1) describe the movement demands of female softball players during defensive and offensive gameplay, with a focus on the frequency and duration of movements occurring and differences between positional groups; 2) determine the reliability of the ForceFrame Hip Strength Testing System in assessing hip and shoulder strength of female softball players unaccustomed to isolated joint isometric measures; 3) assess changes in isometric hip strength in female softball players caused by a repeated batting protocol; and 4) compare changes in isometric strength of female softball players in training and game settings. The outcomes of this thesis will help to establish a description of the movement demands of softball games, which may optimise future softball training and recovery methods. Additionally, data gathered in this thesis will provide a solid foundation for conceptualising neuromuscular fatigue in softball players. These results will thus allow for a greater understanding of athlete preparation.
Study one determined that softball is primarily composed of low intensity activities, like standing or walking, with intermittent periods of high intensity activity (e.g. sprinting, bat swings, high intensity throws). The cumulative effect of these high intensity activities across game durations of two hours or greater, compact tournament schedules and environmental factors may amplify neuromuscular fatigue. Study two concluded that the ForceFrame was a reliable tool in assessing hip and shoulder isometric strength in female diamond-sport athletes, potentially providing sport scientists with a suitable alternative to handheld dynamometers in field-based isometric testing. Study three documented changes in electromyographic amplitude and median frequency, isometric hip strength, and batted ball velocity of female softball players during a repeated batting protocol. Results indicate repeated batting can lead to neuromuscular fatigue and underscores the importance of routine monitoring of softball players in settings with limited recovery. Results of study four demonstrated significant levels of fatigue following softball training and gameplay, as well as evidence of cumulative fatigue in softball players following several games during a multi-day tournament. The results of this study provide the groundwork for determining an appropriate balance between competition-level training and adequate recovery.
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Fontes, Eduardo Bodnariuc 1979. "Limiar de fadiga neuromuscular determinado por diferentes periodos de analise do sinal eletromiografico." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/275157.
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Orientador: Antonio Carlos de Moraes<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Fisica<br>Made available in DSpace on 2018-08-10T17:31:59Z (GMT). No. of bitstreams: 1
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Previous issue date: 2008<br>Resumo: LFNM estabelecido por diferentes períodos de análise do sinal eletromiográfico e comparar os mesmos com a Potência Crítica - PC em indivíduos saudáveis. A amostra foi composta por 17 voluntários saudáveis do sexo masculino (23,4 ± 5,2 anos, 73,6 ± 5,08 kg, 177,8 ± 7,0 cm). Para determinar o LFNM, cada sujeito realizou entre três e quatro cargas constantes no cicloergometro (modelo Corival 400, Quinton Inc, USA) até a exaustão voluntária, com cadência de 60 rpm. Utilizando um eletromiógrafo de 16 canais (MP150, Biopac Systems, Inc., USA), foram coletados sinais EMG do músculo Vasto Lateral. O LFNM foi calculado pelo modelo matemático proposto por (DEVRIES et al., 1982), no qual a taxa de aumento do sinal eletromiográfico atingido durante as cargas constantes é plotado em função das respectivas cargas, sendo o intercepto ¿y¿ do prolongamento desta reta considerado o LFNM. Tal procedimento foi reproduzido para cada um dos tempos de duração de análise, 30 segundos (T30s), um minuto (T1min), dois minutos (T2min) e tempo total (TTotal). PC foi determinada através do modelo hiperbólico. Utilizando a potência de LFNM encontrada por TTotal, foi verificado ainda a capacidade dos voluntários de permanecer em teste retangular de 30 min, sem evidência de fadiga neuromuscular. Foram encontradas diferenças significativas entre os períodos de análise para determinação de LFNM (ANOVA). Utilizando T30s a média alcançada foi 266,7 ± 23,1 W, com T1min ficou em 243,4 ± 16,2 W, para T2min obteve 232,6 ± 18,3 W, e utilizando TTotal a média foi de 217,2 ± 23,1 W, já para PC, foi encontrado valores médios de 177,9 ± 27,3 W. Foram encontradas diferenças estatisticamente significantes entre T30s e todos os outros períodos de análise, T1min, T2min e TTotal (p<0,01). O LFNM determinado com T1min, foi diferente estatisticamente também de TTotal (p<0,01). Todos os períodos de análise utilizados para determinar LFNM superestimaram estatisticamente PC (p<0,01). Foi encontrada correlação significativa apenas para TTotal e PC (R2 = 0,72). Durante o protocolo de carga retangular de 30 minutos, a média da exaustão ocorreu em 661,6 ± 303,9 segundos, apenas um dos voluntários completou os teste de 30 minutos. O nível de significância adotado para todas as análises foi de 5%. A partir dos resultados do presente estudo, é possível concluir que o tempo de análise influencia na determinação de LFNM, superestimando PC e a capacidade de adultos jovens em realizar exercícios de carga constante de 30 minutos em cicloergômetro<br>Abstract: The purpose of this study was to establish the Neuromuscular Fatigue Threshold - LFNM determinied by different analysis periods of electromyography sign and compare to the Critical Power - CP in healthy young men. 17 healthy men volunteers (23,4 ± 5,2 years, 73,6 ± 5,08 kg, 177,8 ± 7,0 cm) completed three or four constant loads tests on a cycling ergometer to establish LFNM (model Corival 400, Quinton Inc, USA) until exhaustion, and the pedal cadence was 60 rpm. Using an amplifier with 16 channels (MP150, Biopac Systems, Inc., USA), were collected EMG signs from Vastus Lateralis muscle from the dominant side. The LFNM were calculated by the mathematical model proposed by DeVries et al., (1982) where the LFNM was considered the y intercept of the regression line the EMG slopes from contant load tests plotted against its respective load. CP was calculated using the hyperbolic equation model. The LFNM procedure was done by each period of EMG analysis 30 seconds (T30s), one minute (T1min), two minutes (T2min) and total period (TTotal). Using LFNM established by TTotal, were verified the capacity of the volunteers to complete a 30 minutes constant load test, without neuromuscular fatigue. ANOVA found statistical differences between analysis periods. Using T30s, the mean found were 266,7 ± 23,1 W, with T1mn were 243,4 ± 16,2 W, for T2min were 232,6 ± 18,3 W, and with TTotal, the mean were 217,2 ± 23,1 W, however, for CP were found 177,9 ± 27,3 W. Were found statistical differences between T30s and all the others analysis periods, T1min, T2min and Total (p<0,01). The LFNM established by T1min were also different from TTotal (p<0,01). All the analysis periods overestimated PC (p<0,01). Were found significant correlation between only PC and TTotal (R2 = 0,72). During the 30 minutes constant load test completed, the exhaustion mean time were 661,6 ± 303,9 seconds, and only one volunteer completed all the 30 minutes. The significance level adopted for all analysis was 5%. According to the results of this study, it is possible to conclude that the analysis periods influences the determination of LFNM, and it overestimates CP and the capacity of the healthy adults to complete a 30 minutes constant load test in cycling ergometer<br>Mestrado<br>Ciencia do Desporto<br>Mestre em Educação Física
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Santos, Denise Veck dos. "Análise das variáveis biomecânicas em mulheres ativas após aplicação de um protocolo de fadiga /." Rio Claro, 2019. http://hdl.handle.net/11449/191096.
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Orientador: Adalgiso Coscrato Cardozo<br>Resumo: No cenário esportivo a avaliação de padrões de movimentos é indispensável para melhoria do desempenho, prevenção e recuperação de lesões. Dentre as variáveis que podem ser estudadas, a Eficiência Neuromuscular (ENM) vem ganhando espaço no meio acadêmico devido à sua importância para compreender como os fatores neurais interferem na eficácia da ativação das unidades motoras durante a contração muscular. A eficiência neuromuscular está relacionada à ativação de fibras musculares e à produção de força, gerada por um determinado músculo. Um dos fatores que podem interferir na ENM comprometendo as ações durante as diferentes práticas desportivas é a fadiga. A fadiga pode ser considerada como uma falha para manter um nível desejado de desempenho ou trabalho durante uma atividade repetitiva ou sustentada. O objetivo do presente estudo é analisar variáveis neuromusculares em mulheres ativas após a aplicação de um protocolo de fadiga e verificar a diferença na dominância entre membros inferiores. Participaram do estudo 20 mulheres ativas, com idade entre 18 e 35 anos. O estudo foi divido em 2 experimentos. No primeiro experimento foram realizados testes de contração isométrica voluntária máxima e manutenção de cargas (20%, 40%, 60% e 80% da CIVM) no membro dominante. Após a avaliação as voluntárias foram submetidas a um protocolo de fadiga. Os testes foram refeitos imediatamente após para analisar o efeito da fadiga nas variáveis da eficiência neuromuscular, no desvio padrão e coefici... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: In the sports scenario, the evaluation of movement patterns is indispensable for performance improvement, injury prevention and recovery. Among the variables that can be studied, the Neuromuscular Efficiency (ENM) has been gaining ground in the academic environment due to its importance to understand how the neural factors interfere in the effectiveness of motor unit activation during muscle contraction. Neuromuscular efficiency is related to the activation of muscle fibers and the production of force generated by a given muscle. One of the factors that can interfere with ENM compromising actions during different sports is fatigue. Fatigue can be considered a failure to maintain a desired level of performance or work during a repetitive or sustained activity. The aim of the present study is to analyze neuromuscular variables in active women after the application of a fatigue protocol and to verify the difference in lower limb dominance. The study included 20 active women, aged between 18 and 35 years. The study was divided into 2 experiments. In the first experiment, maximum voluntary isometric contraction tests and load maintenance (20%, 40%, 60% and 80% of MVIC) were performed on the dominant limb. After the evaluation, the volunteers were submitted to a fatigue protocol. The tests were redone immediately afterwards to analyze the effect of fatigue on neuromuscular efficiency variables, standard deviation and coefficient of variation. In the second experiment, voluntary max... (Complete abstract click electronic access below)<br>Mestre
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Hoeven, Johannes Harmen van der. "Conduction velocity in human muscle an EMG study in fatigue and neuromuscular disorders /." [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1995. http://irs.ub.rug.nl/ppn/142995223.
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Forsberg, Josefin. "Muscle fatigue and neuromuscular knee valgus in strong versus weak young female athletes." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-33981.
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Background. Knee injuries such as anterior cruciate ligament injuries (ACL) are common in young female athletes resulting in great medical and personal costs. Both knee valgus and muscle fatigue has been reported to increase the risk of injury, while strength training has been used to reduce the occurrence of knee valgus and injury. However, few data exist on the impact of muscle strength and fatigue on knee valgus. Aim. The study aimed at investigating whether muscle strength affects the presence of knee valgus and if fatigue affects knee valgus differently depending on the level of muscle strength in young female athletes. Methods. Twenty young female athletes, mean age 18,15 (±0,79) years, participated in this study. A unilateral drop jump, video analysed in 2-dimensional, was used to evaluate knee valgus and a one Repetition Maximum (1RM) in squat was used to determine the level of muscle strength. A fatigue protocol was used to achieve muscle fatigue before another unilateral drop jump was performed. The subjects were dichotomised, by the 1 RM according to the median, to analyse ‘weak’ versus ‘strong’ females. Both the right leg (RL) and the left leg (LL) were measured before and after fatigue. Results. No significant differences, in the degree of knee valgus, were found between strong and weak group before (RL, p=0.6, LL, p=0.11), or after (RL, p=0.97, LL p=0.36) fatigue. There was also no significant difference in how fatigue affected knee valgus between strong and weak group (RL, p=0.5, LL, p=0.38). Conclusion. The present study suggests that there is no difference in knee valgus between strong and weakfemale athletes. In addition, fatigue does not seem to have an impact on knee valgus in neitherstrong nor weak females. This study has limited number of subjects and further studies are needed.<br>Bakgrund. Knäskador såsom främre korsbandsskada (ACL) är vanliga hos unga idrottande kvinnor och bidrar till höga medicinska kostnader och personligt lidande. Knävalgus och muskelutmattning har var för sig visat sig öka risken för knäskador hos kvinnor, medan styrketräning har rapporterats kunna minska förekomsten av knävalgus och risken för skada. Emellertid finns få studier som undersöker effekterna av muskelstyrka och utmattning på knävalgus. Syfte. Studien syftar till att undersöka huruvida styrka påverkar förekomsten av knävalgus och om muskulär trötthet påverkar knävalgus olika beroende på nivå av muskelstyrka hos unga idrottande kvinnor. Metod. Tjugo unga kvinnliga idrottare deltog i studien, ålder 18,15 (±0,79). Ett enbenshopp, vilket filmades med videokamera, användes för att utvärdera knävalgus och en repetition maximum (1RM) i knäböj för att bestämma maximal muskelstyrka. Ett utmattningsprotokoll användes för att åstadkomma muskeltrötthet. Genom att dela styrkevariabeln, 1 RM testet, vid medianen delades försökspersonerna in i två grupper; starka och svaga. Samtliga försökspersoner testade både höger och vänster ben innan och efter utmattning. Resultat. Resultaten visade ingen signifikant skillnad mellan stark och svag grupp gällande graden av knävalgus, i varken höger (p= 0,6) eller vänster (p= 0,97) ben före utmattning. Inte heller var det någon skillnad mellan stark och svag grupp efter utmattning (höger ben, p= 0,11, vänster ben, p= 0,36). Inte heller kunde någon signifikant skillnad konstateras angående utmattningens effekt på knävalgus beroende på styrka, stark/svag (höger ben, p= 0,5, vänster ben, p= 0,38). Slutsats. Sammanfattningsvis verkar det inte föreligga någon skillnad i förekomst av knävalgus mellan starka och svaga individer. Således verkar det som att muskelstyrka saknar betydelse för knävalgus hos unga kvinnliga idrottare. Vidare verkar inte heller utmattning påverka knävalgus hos varken starka eller svaga unga kvinnliga idrottare. Studien har begränsat antal deltagare och fler studier krävs.
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Riding, Teri J. "Contributions of muscle fatigue to a neuromuscular neck injury in female standard ballroom dancers /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1529.pdf.
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Theilen, Nicholas Todd. "Comparisons of acute neuromuscular fatigue and recovery after maximal effort strength training using powerlifts." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4593.
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COMPARISONS OF ACUTE NEUROMUSCULAR FATIGUE IN MAXIMAL EFFORT STRENGTH TRAINING USING POWERLIFTS.
N. T. Theilen, B. I. Campbell, M. C. Zourdos2, J. M. Oliver3, J. O'Halloran1, N. Asher1, J. M. Wilson4
1University of South Florida, Exercise and Performance Nutrition Laboratory, Tampa, FL
2Florida Atlantic University, Boca Raton, FL
3Texas Christian University, Fort Worth, TX
4University of Tampa, Tampa, FL
Neuromuscular fatigue is associated with a decrease in velocity. Following powerlift training, the extent to which fatigue affects the performance velocity of each lift after a specified recovery interval has not yet been investigated.
Purpose
To assess the level of acute neuromuscular fatigue, as measured by a decrease in peak velocity, as a result of maximal effort strength training sessions with each powerlift.
Methods
Twelve resistance trained males (22.8 ± 2.6 yrs; 177.1 ± 6.7 cm; 83.0 ± 12.6 kgs) participated in a randomized crossover design with three conditions: Squat (SQ), Bench Press (BP), and Deadlift (DL). Subjects' relative strength included the ability to successfully complete at least 1.5x their bodyweight in the squat exercise. Initially, baseline peak velocity (PV) was measured for each lift at 60% 1RM via a TENDO unit. One training session occurred each Monday for 3 consecutive weeks (1 week for each lift). Each training session consisted of a 1RM of the designated lift followed by 4 sets of 2 repetitions at 92.5% and 4 sets of 3 repetitions at 87.5%. Following training sessions, each lift PV was measured at 24, 48, and 72 hours post-training to compare with baseline measures and determine recovery. Data was analyzed using a repeated measures ANOVA (p<.05).
Results
SQ: No significant differences in PV of the SQ and DL following SQ training at each time point compared to baseline. Bench press PV significantly declined following squat training (Baseline = 1.069 m/s; 24 hours = 0.974 m/s [p = 0.019]; 48 hours = 1.015 m/s [p = 0.034]; 72 hours = 0.970 m/s [p = 0.004].
BP: No significant differences in PV of the SQ and DL following BP training at each time point compared to baseline. Bench press PV significantly declined only at 24 hours following BP training (Baseline = 1.069 m/s; 24 hours = 0.988 m/s [p = 0.004]).
DL: No significant differences in PV of the DL following DL training as compared to baseline. Squat PV significantly declined at 24 hours following the DL training (Baseline = 1.384 m/s; 24 hours = 1.315 m/s [p = 0.032]. Similar to SQ, PV of the BP significantly declined only at 24 hours following DL training (Baseline = 1.069 m/s; 24 hours = 0.979 m/s [p < 0.001]).
Conclusions
Bench press PV was significantly decreased 24-hours following each of the three powerlifts as compared to baseline values. Interestingly, there were no changes in squat and deadlift PV following training of that specific lift.
Practical Applications
Regardless of the powerlift trained, bench press PV at 60% was compromised 24-hours later. Therefore, following training of any powerlift, more than 24-hours may be needed to optimize performance in the BP at submaximal intensities.
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Pethick, Jamie. "The effects of neuromuscular fatigue on the complexity of isometric torque output in humans." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/60067/.
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The temporal structure, or complexity, of torque output is thought to reflect the adaptability of motor control and has important implications for system function, with high values endowing greater adaptability in response to alterations in task demand. The aim of this thesis was to investigate the effect of neuromuscular fatigue on the complexity of isometric muscle torque output. It was hypothesised that neuromuscular fatigue would lead to a reduction in the complexity of muscle torque output, as measured by approximate entropy (ApEn), sample entropy (SampEn) and the detrended fluctuation analysis (DFA) α scaling exponent. The first experimental study (Chapter 4) demonstrated that muscle torque complexity was significantly reduced during both maximal and submaximal intermittent fatiguing contractions, with the values at task failure indicative of increasingly Brownian noise (DFA α > 1.50). It was subsequently shown in the second study (Chapter 5) that this reduction in complexity occurred exclusively during contractions performed above the critical torque. It was next demonstrated, in the third study (Chapter 6), that pre-existing fatigue significantly reduced torque complexity and time to task failure, but still resulted in consistent values of complexity at task failure regardless of the time taken to reach that point. In the fourth study (Chapter 7) caffeine ingestion was found to slow the rate of reduction in torque complexity with fatigue, seemingly through both central and peripheral mechanisms. Finally, in the fifth study (Chapter 8) eccentric exercise decreased the complexity of torque output, with values only recovering to baseline levels after 24 hours recovery, in comparison to only 10 minutes recovery following isometric exercise. These results demonstrate that torque complexity is significantly perturbed by neuromuscular fatigue. This thesis has thus provided substantial evidence that the complexity of motor control during force production becomes less complex, and that muscles become less adaptable, with neuromuscular fatigue.
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Riding, Teri. "Contributions of Muscle Fatigue to a Neuromuscular Neck Injury in Female Standard Ballroom Dancers." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/755.
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Objective: To investigate the potential etiology of a loss of neck control injury in female standard ballroom dancers. The median frequency (MF) as measured by electromyography (EMG) of the left upper trapezius (UT), left splenius capitius (SPL), and right sternocleidomastoid (SCM) of injured dancers was compared to non-injured dancers. This comparison was performed to identify whether dancers with a history of loss of neck control have a greater amount of fatigue than those with no history of this particular injury. Design and Setting: A 2 x 6 factorial design was used for this investigation. The independent variables were group (injured vs. non-injured) and time (before and after the three rounds of dancing). The dependent variables were MF as measured by EMG, range of motion, and neck length. All testing was performed at the university biomechanics laboratory and ballroom dance studio. Subjects: Twenty female subjects (10 injured group {mean height 167.40 ± 4.12 cm and weight 59.30 ± 5.41 kg}, 10 non-injured group {mean height 166.76 ± 4.62 cm and weight 58.93 ± 5.30 kg}), with at least one year experience in competitive ballroom dancing, in the standard division participated in this study. All subjects competed at a Dancesport competition either in the novice, pre-championship, and/or amateur standard classifications. Inclusion criteria for the injured group included female ballroom dancers who had a loss of neck control episode. Measurements: Surface EMG activity was recorded from the left UT, left SPL, and right SCM muscles before and after dancing the five standard dances. Results: The decrease in EMG MF was not significant between groups. There was no difference in neck lengths from the external occipital protuberance to inferior angle of the scapula between groups. There were also no significant differences in range of motion of left and right lateral flexion and extension in either group from pre to post dancing. Conclusions: Based on the results of this study, subjects with a history of neuromuscular neck injury did not appear to have acute fatigue of the three muscles studied here following the routine used in this study.
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Garnier, Yoann. "Influence des modalités de contraction musculaire sur les effets neuroplastiques de l'exercice." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK034/document.
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Parallèlement aux adaptations cardiovasculaires et neuromusculaires, les exercices mono-articulaires ou locomoteurs peuvent induire des changements neuroplastiques de muscles impliqués ou non dans l’exercice. Si l’effet de paramètres de l’exercice, comme l’intensité ou la durée, sur les changements neuroplastiques ont déjà été étudiés, l’effet du mode de contraction musculaire reste, quant à lui, moins connu. L’objectif de cette thèse a été d’évaluer les effets du mode de contraction musculaire sur les changements neuroplastiques consécutifs à un exercice locomoteur ou mono-articulaire. La première étude a montré que l’augmentation de l’excitabilité corticospinale d’un muscle non-impliqué dans l’exercice (muscle de la main), observée suite à un exercice de marche/ course, n’était pas modulée par le mode de contraction des muscles extenseurs du genou. En revanche, une modulation spécifique des réseaux intracorticaux par le mode de contraction impliqué lors d’un exercice a été mise en évidence par l’application d’un protocole de stimulation associative jumelée. Des observations similaires ont été faites dans une seconde étude investiguant les changements corticospinaux observés au niveau des muscles extenseurs du genou impliqués dans des exercices mono-articulaires fatigants, effectués dans un mode de contraction concentrique ou excentrique. Une troisième étude a montré que pour un exercice de marche/ course réalisé à même fréquence cardiaque en montée, à plat ou en descente, la modalité en descente induisait une fatigue musculaire des extenseurs du genou plus importante, avec des altérations contractiles plus marquée. La quatrième étude a montré que seule la modalité en descente induisait une augmentation de l’excitabilité corticospinale, et une réduction de l’inhibition corticale des muscles extenseurs du genou. Les travaux de cette thèse proposent que le mode de contraction musculaire lors d’un exercice n’est, en lui-même, pas un facteur prépondérant des changements neuroplastiques observés pour des muscles impliqués dans l’exercice. Ces changements neuroplastiques seraient au contraire dépendant de la magnitude de la fatigue neuromusculaire induite, elle-même dépendante du mode de contraction musculaire<br>Along with cardiovascular and neuromuscular changes, mono-articular and locomotor exercises may induced neuroplastic changes from muscles involved, or non-involved, in the exercise. If the effect of exercise intensity or duration on neuroplastic changes has been previously investigated, the effect of the mode of muscle contraction remains unclear. The aim of this thesis was to investigate the effects of the mode of muscle contraction on neuroplastic changes induced a locomotor or a single-joint exercise. The first study showed that the increase in the corticospinal excitability of a non-exercised hand muscle, observed after a walking/ running exercise, was not modulated by the knee extensors mode of muscle contraction. However, a specific modulation of the intracortical networks by the mode of muscle contraction was evidenced using a paired-associative stimulation protocol. Similar findings were made in a second study that investigated corticospinal changes in the knee extensors following a fatiguing single-joint exercise, performed in either a concentric or an eccentric mode of muscle contraction. A third study showed that for a walking/ running exercise performed at the same heart rate in either a inline, a level or a decline condition, the latter condition induced a greater magnitude of neuromuscular fatigue of the knee extensors, with greater contractile impairments. The fourth study reported that only a decline exercise induced an increase in the corticospinal excitability, and a reduction of the cortical inhibition of the knee extensors. Altogether, findings from this thesis suggest that the mode of muscle contraction during an exercise is not, per se, a main factor responsible for neuroplastic changes observed in exercised muscles. Rather, these changes may depend upon the magnitude of neuromuscular fatigue induced, which could depend upon the mode of muscle contraction involved during exercise
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Dwyer, Daniel, and na. "Serotonin as a Mediator of Fatigue During Exercise and Training." Griffith University. School of Health Science, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040521.130535.
Full textAbstract:
Exercise has been shown to cause an increase in the concentration of brain serotonin (5-hydroxytryptamine, 5-HT) in humans and experimental animals. The increase in brain serotonin coincides with the onset of fatigue and is referred to as "central fatigue". Experiments in humans and animals involving serotonin receptor agonists have demonstrated reductions in exercise performance by simulating the exercise-induced increase in endogenous serotonin. Conversely, the administration of serotonin receptor antagonists has been shown to extend exercise performance in experimental animals, but not in humans. Although the relationship between the concentration of brain serotonin and exercise performance is well described in the literature, the precise effect of central fatigue on muscle function per se is unclear. Furthermore, there appear to be differences in serotonergic function between trained and untrained cohorts. However, it is not clear whether the differences are due to a training adaptation or if the differences are inherent in the individual. In addition, the time course of these adaptations and the mechanisms of adaptation are not known. The initial purpose of this thesis was to determine whether six weeks of endurance exercise training had any effect on central serotonin receptor sensitivity in Wistar rats. The rats ran on a treadmill 4 times per week with 2 exercise tests of endurance performance per week. Receptor sensitivity was determined indirectly, at the end of each training week, by the reduction in endurance performance, under the influence of a 5-HT1a agonist, (m-Chlorophenylpiperazine, m-CPP). Improved tolerance to the fatiguing effects of the serotonin agonist would suggest desensitisation of central serotonin receptors, probably 5-HT1a receptors. Two groups of controls were used to examine, i) the effect of the injection per se on exercise performance and ii) changes in serotonin receptor sensitivity associated with maturation, in the absence of any exercise training. In the training group, undrugged exercise performance significantly improved by 47% after 6 weeks of training (mean ± SEM, 4518 ± 729 s vs. 6640 ± 903 s, p=0.01). Drugged exercise performance also increased significantly from week 1 to week 6 (306 ± 69 s to 712 ± 192 s, p=0.004). Control group results indicated that the dose of m-CPP alone caused fatigue during exercise tests and that maturation was not responsible for any decrease in receptor sensitivity. Endurance training appears to stimulate an adaptive response to the fatiguing effects of increased brain serotonin, which may enhance endurance exercise performance. The purpose of the second set of experiments described in this thesis was to investigate changes in serotonin receptor sensitivity in response to exercise training in human subjects. Twelve male volunteers completed 30 minutes of stationary cycling at 70% of VO2peak, on 3 days per week, for 9 weeks. Serotonin receptor sensitivity was assessed indirectly by measuring the prolactin response to a serotonin receptor agonist (buspirone hydrochloride), using a placebo controlled, blind cross-over design. A sedentary group of control subjects were also recruited to control for possible seasonal variations in serotonin receptor sensitivity. Endurance capacity was also assessed as time to exhaustion while cycling at 60% of VO2peak. The exercise training caused a significant increase in aerobic power (VO2peak, 3.1±0.16 to 3.6±0.15 L.m-1, p< 0.05) and endurance capacity (93±8 to 168±11 min, p<0.05), but there was no change (p>0.05) in the prolactin response to a serotonin agonist. However, 25% of the subjects in the training group demonstrated a decrease in receptor sensitivity, as indicated by a decrease in prolactin response. These results suggest that while the exercise training caused an increase in aerobic power and endurance capacity, there was no measurable change in 5-HT receptor sensitivity. In addition, it is possible that changes in receptor sensitivity may take longer to occur, the training stimulus used in the present investigation was inadequate or that changes occurred in other 5-HT receptor subtypes that were not assessed by the present methodology. The third set of experiments described here, investigated the changes in neuromuscular function under the influence of a serotonin receptor agonist (buspirone hydrochloride). Subjects were administered the agonist or a placebo in a blind cross over design. Measures of neuromuscular function included reaction time (RT), hand eye coordination (HEC), isometric neuromuscular control (INC), maximal voluntary isometric contractile force (MVIC-F), isometric muscular endurance capacity (IMEC) and various electromyographic (EMG) indices of fatigue in biceps brachii. A preliminary experiment was conducted to determine a drug dose that did not cause sedation of the research subjects. The agonist caused a significant (p<0.05) decrease in MVIC-F, INC and IMEC. There was a non significant (p = 0.08) decrease in EMG amplitude during the MVIC-F trial with the agonist, compared to the effect of the placebo. The median EMG frequency during the IMEC test was also significantly less with the agonist, when compared to the placebo effect. There was a decline in RT and HEC, although this was not significant. These findings indicate that a serotonin receptor agonist causes a decrease in neuromuscular function during isometric muscle contractions. The decrements in muscle function reported in this study may help to explain previous reports of an association between increased brain serotonin concentration and a reduction in endurance performance. Although the present study does not exclude the possibility that an increase in brain serotonin does cause fatigue by affecting organs peripheral to the brain, it provides evidence of fatigue within the central nervous system. Further examination of the effect of a serotonin agonist on muscle function during non-isometric muscle contractions is warranted.
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Dwyer, Dan. "Serotonin as a Mediator of Fatigue During Exercise and Training." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/366705.
Full textAbstract:
Exercise has been shown to cause an increase in the concentration of brain serotonin (5-hydroxytryptamine, 5-HT) in humans and experimental animals. The increase in brain serotonin coincides with the onset of fatigue and is referred to as "central fatigue". Experiments in humans and animals involving serotonin receptor agonists have demonstrated reductions in exercise performance by simulating the exercise-induced increase in endogenous serotonin. Conversely, the administration of serotonin receptor antagonists has been shown to extend exercise performance in experimental animals, but not in humans. Although the relationship between the concentration of brain serotonin and exercise performance is well described in the literature, the precise effect of central fatigue on muscle function per se is unclear. Furthermore, there appear to be differences in serotonergic function between trained and untrained cohorts. However, it is not clear whether the differences are due to a training adaptation or if the differences are inherent in the individual. In addition, the time course of these adaptations and the mechanisms of adaptation are not known. The initial purpose of this thesis was to determine whether six weeks of endurance exercise training had any effect on central serotonin receptor sensitivity in Wistar rats. The rats ran on a treadmill 4 times per week with 2 exercise tests of endurance performance per week. Receptor sensitivity was determined indirectly, at the end of each training week, by the reduction in endurance performance, under the influence of a 5-HT1a agonist, (m-Chlorophenylpiperazine, m-CPP). Improved tolerance to the fatiguing effects of the serotonin agonist would suggest desensitisation of central serotonin receptors, probably 5-HT1a receptors. Two groups of controls were used to examine, i) the effect of the injection per se on exercise performance and ii) changes in serotonin receptor sensitivity associated with maturation, in the absence of any exercise training. In the training group, undrugged exercise performance significantly improved by 47% after 6 weeks of training (mean ± SEM, 4518 ± 729 s vs. 6640 ± 903 s, p=0.01). Drugged exercise performance also increased significantly from week 1 to week 6 (306 ± 69 s to 712 ± 192 s, p=0.004). Control group results indicated that the dose of m-CPP alone caused fatigue during exercise tests and that maturation was not responsible for any decrease in receptor sensitivity. Endurance training appears to stimulate an adaptive response to the fatiguing effects of increased brain serotonin, which may enhance endurance exercise performance. The purpose of the second set of experiments described in this thesis was to investigate changes in serotonin receptor sensitivity in response to exercise training in human subjects. Twelve male volunteers completed 30 minutes of stationary cycling at 70% of VO2peak, on 3 days per week, for 9 weeks. Serotonin receptor sensitivity was assessed indirectly by measuring the prolactin response to a serotonin receptor agonist (buspirone hydrochloride), using a placebo controlled, blind cross-over design. A sedentary group of control subjects were also recruited to control for possible seasonal variations in serotonin receptor sensitivity. Endurance capacity was also assessed as time to exhaustion while cycling at 60% of VO2peak. The exercise training caused a significant increase in aerobic power (VO2peak, 3.1±0.16 to 3.6±0.15 L.m-1, p< 0.05) and endurance capacity (93±8 to 168±11 min, p<0.05), but there was no change (p>0.05) in the prolactin response to a serotonin agonist. However, 25% of the subjects in the training group demonstrated a decrease in receptor sensitivity, as indicated by a decrease in prolactin response. These results suggest that while the exercise training caused an increase in aerobic power and endurance capacity, there was no measurable change in 5-HT receptor sensitivity. In addition, it is possible that changes in receptor sensitivity may take longer to occur, the training stimulus used in the present investigation was inadequate or that changes occurred in other 5-HT receptor subtypes that were not assessed by the present methodology. The third set of experiments described here, investigated the changes in neuromuscular function under the influence of a serotonin receptor agonist (buspirone hydrochloride). Subjects were administered the agonist or a placebo in a blind cross over design. Measures of neuromuscular function included reaction time (RT), hand eye coordination (HEC), isometric neuromuscular control (INC), maximal voluntary isometric contractile force (MVIC-F), isometric muscular endurance capacity (IMEC) and various electromyographic (EMG) indices of fatigue in biceps brachii. A preliminary experiment was conducted to determine a drug dose that did not cause sedation of the research subjects. The agonist caused a significant (p<0.05) decrease in MVIC-F, INC and IMEC. There was a non significant (p = 0.08) decrease in EMG amplitude during the MVIC-F trial with the agonist, compared to the effect of the placebo. The median EMG frequency during the IMEC test was also significantly less with the agonist, when compared to the placebo effect. There was a decline in RT and HEC, although this was not significant. These findings indicate that a serotonin receptor agonist causes a decrease in neuromuscular function during isometric muscle contractions. The decrements in muscle function reported in this study may help to explain previous reports of an association between increased brain serotonin concentration and a reduction in endurance performance. Although the present study does not exclude the possibility that an increase in brain serotonin does cause fatigue by affecting organs peripheral to the brain, it provides evidence of fatigue within the central nervous system. Further examination of the effect of a serotonin agonist on muscle function during non-isometric muscle contractions is warranted.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Health Sciences<br>Full Text
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Followay, Brittany. "EFFECTS OF CYCLING EXERCISE AND COLD EXPOSURE ON NEUROMUSCULAR ACTIVATION AND FATIGUE,AND METABOLIC RESPONSES." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1531736690094866.
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Cometti, Carole. "Effets de différents paramètres de récupération lors d'exercices de renforcement musculaire." Thesis, Dijon, 2012. http://www.theses.fr/2012DIJOS014/document.
Full textAbstract:
L’optimisation de la performance oblige l’athlète à répéter des séances d’entraînement à haute intensité de travail avec peu de récupération, ce qui génère une fatigue neuromusculaire qui peut être préjudiciable. Ainsi, dans le but de limiter ce phénomène et d’améliorer l’efficacité des séances d’entraînement, le choix d’une récupération adéquate s’impose.La récupération active est la méthode la plus connue et la plus efficace relatée dans la littérature. En effet, de nombreuses études démontrent son effet bénéfique sur la fatigue provoquée lors d’exercices globaux (types course ou pédalage). Cette modalité de récupération correspond à un exercice musculaire léger permettant une augmentation du flux sanguin périphérique et une élimination plus rapide des métabolites. A l’heure actuelle, peu d’études se sont intéressées à la récupération active appliquée de manière locale pour des exercices de renforcement de groupes musculaires spécifiques.L’objectif de ce travail était donc d’étudier la méthode la plus efficace, en termes de modalité et de moment d’application, pour récupérer la force maximale de l’athlète lors d’un exercice de renforcement musculaire. De plus, afin d’assurer une application de cette récupération active, spécifiquement sur les groupes musculaires souhaités, nous avons utilisé l’électromyostimulation (EMS).Nos différents résultats suggèrent qu’il n’est pas nécessaire d’appliquer une modalité particulière pour la récupération des exercices de renforcement musculaire réalisés à intensité maximale. En effet, la récupération active par EMS appliquée au cours d’une séance (entre les séries) ou après une séance ne montre pas de différence avec une récupération passive. De plus, l’application proximale ou distale de l’EMS n’a pas d’influence sur la cinétique de récupération. L’approche neuromusculaire de la fatigue, montre cependant, qu’il s’avère nécessaire d’analyser l’origine des perturbations engendrées par l’exercice, afin de choisir la modalité de récupération la mieux adaptée<br>The high frequency of resistance training sessions induces heavy strain and fatigue phenomenon, which could be prejudicial for subsequent performance. In this context, it appears necessary to apply proper recovery strategies in order to improve the athlete’s ability to regain an adequate working state for subsequent training.Active recovery is widely described in the literature as the most efficient method for this purpose. It consists in low-intensity exercises, which could improve metabolites washout by increasing peripheral blood flow. To our knowledge, active recovery is usually applied globally, with exercises involving the whole body (light pedalling or running) but little is known regarding a local application after analytical exercises such as strengthening exercise. The aim of our research was therefore to determine the most effective method to recover from resistance training session in terms of maximal strength performance. Among the active recovery modes, electromyostimulation (EMS) is of particular interest since it can be applied on specific muscles groups. Our results showed that active recovery using EMS applied during a session (between the sets) or after a session, did not demonstrate any difference as compared with passive recovery. Also, we demonstrated that EMS was not more efficient when applied distally. However, we highlighted that the investigation of neuromuscular parameters is necessary to better understand the origin of the fatigue induced by a specific exercise in order to apply the most appropriated recovery mode
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Bray, James William. "Quantification of training load, neuromuscular fatigue, biochemical and endocrine responses to fast bowling in cricket." Thesis, University of Hull, 2017. http://hydra.hull.ac.uk/resources/hull:16447.
Full textAbstract:
Recent professionalization, the emergence of, and ever-increasing popularity of limited overs cricket, have resulted in traditional playing schedules evolving and expanding. Consequently, players now compete for much of the year, experiencing periods of condensed fixtures. To meet these increased demands, the aforementioned contribute to effecting team performance and player health. Thus, the prevalence of injuries, especially amongst fast bowlers, has been shown and attributed to rises in competition workloads. Therefore, the main aim of this thesis was to explore the application of micro-electro-mechanical systems (MEMS) to quantify the training load of fast bowlers. Furthermore, I sought to assess relationships between both internal and external training load variables and proposed markers of fatigue and recovery. The first preliminary descriptive research study (Chapter 4) aimed to prospectively quantify fast bowling workloads during a typical season of professional domestic county cricket (April – September). Data were collected from fixture scorebooks, with descriptive bowling workloads determined by calculating frequencies of overs and deliveries bowled. This was further calculated dependant on both bowler classification (opening [O-B; n = 2] or support [S-B; n = 6]) and competition format (multiday [MD], One-day [OD] or Twenty20 [T20]), respectively. Significant differences were found in total number of overs (296.1 overs; 95% CI 37.8 to 554.4; P = 0.03) and deliveries (1764.8 balls; 95% CI 183.0 to 3346.7; P = 0.03) bowled between O-B and S-B, respectively. Multiday cricket was the only format where, significant differences between bowlers were found; total number of overs (289.9 overs; 95% CI 88.2 to 491.6; P = 0.01) and deliveries (1739.3 balls; 95% CI 529.3 to 2949.3; P = 0.01) bowled. The aim of experimental study one (Chapter 5) was to assess the between-match and within-match between-over variability of external training load measures during T20 cricket competition. MEMS data were collected from eight fast bowlers in 17 matches of domestic T20 competition, spanning two seasons. MEMS variables were categorised into total distance (TD), low- (≤ 14.4 km.h-1) and high- (≥ 14.4 km.h-1) speed running distance, total sprint distance (≥18 km.h-1), number of sprint efforts and PlayerLoadTM ([PL] arbitrary units; AU). Data were log-transformed to provide the coefficient of variation (CV; expressed as percentages). The between-match variability was greatest in high-speed running distance (32.9% CV), total sprint distance (49.0% CV) and number of sprint efforts (48.0% CV). Similarly, within-match between-over high-speed running distance (12.8% CV), total sprint distance (17.1% CV) and number of sprint efforts (12.3% CV) elicited the greatest variability, yet, this was markedly reduced compared to between-match observations. However, TD and PL were found to be relatively stable measures of external training load (range; 5.5–13.3% CV), both between-match and within-match between-over. Experimental study two (Chapter 6) investigated short-term neuromuscular fatigue (NMF) of fast bowlers and relationships to match performance during a typical season of professional academy OD limited overs cricket. Baseline measures of lower body NMF were assessed via flight time (ms) from a countermovement jump (CMJ). These measures were repeated every morning of competition; NMF was additionally assessed within 30-min after the cessation of the bowling innings (CMJ-FIRST or CMJ-SECOND). MEMS data were collected from six fast bowlers, with supplementary descriptive fast bowling workloads classifications (LOW, MODERATE and HIGH). There were significant reductions in flight time pre to post bowling innings (Δ 19 ms; P = 0.008). Moreover, similar reductions in flight time were found in LOW – MODERATE (Δ 30 ms; P = 0.03) and LOW – HIGH bowling workload groups (Δ 43 ms; P = 0.003), respectively. Finally, experimental study three (Chapter 7) investigated neuromuscular, biochemical and endocrine markers of fatigue after four spells of simulated fast bowling. Eleven fast bowlers completed differing spells of simulated fast bowling based on the Cricket Australia-Australian Institute of Sport (CA-AIS) fast bowling skills test. NMF were assessed via flight-time from a CMJ; pre (-0.5-h) and post (+0.5 and +24-h) simulation, with blood (Creatine kinase; CK) and saliva (Cortisol; sCort) samples collected in parallel. During each simulated fast bowling trial (4-, 6-, RANDOM- & 10-overs), internal (heart rate exertion index [HREI]) and external (PL) training load was quantified using MEMS. There were small, significant reductions in CMJ flight time pre to post (Δ 21 ms; P < 0.01) and pre to 24-h post (Δ 8 ms; P = 0.001) simulation, respectively. Overs bowled appeared to significantly affect NMF for up to 24-h post simulation. Furthermore, changes in CK were found to best correlate with estimated TD (r = 0.48; P = 0.002) rating of perceived exertion (RPE r = 0.47; P = 0.002) session-RPE (r = 0.48; P = 0.002), HREI (r = 0.45; P = 0.003) and PL (r = 0.41; P = 0.009) 24-h post simulation, respectively. The findings of this thesis demonstrate that during limited overs cricket, high-speed locomotive activity is highly variable amongst fast bowlers. Furthermore, fast bowlers are shown to experience short-term NMF, which appears to be magnified based on descriptive fast bowling workload characteristics. Collectively, these findings have importance for practitioners, who seek to facilitate performance by informed training prescription based on replicating match and training demands.
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Fell, Neil. "Neuromuscular and metabolic characteristics of fatigue in response to heavy resistance and dynamic strength training." Thesis, Liverpool John Moores University, 2004. http://researchonline.ljmu.ac.uk/5601/.
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Vitry, Florian. "Effets aigus et chroniques de l’électrostimulation appliquée au niveau du nerf moteur : importance du retour afférent." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK087.
Full textAbstract:
L'objectif de cette thèse était d’étudier l'impact de protocoles d’électrostimulation favorisant un recrutement indirect des unités motrices (UM) via les afférences sensorielles et induisant le développement d’extra force, sur le système neuromusculaire. Ces protocoles associent une grande largeur d’impulsion, une faible intensité de stimulation, des hautes et basses fréquences et sont appliqués sur le nerf moteur. L’étude des effets de ces protocoles sur la fatigue neuromusculaire lors d’une application aiguë a fait l’objet de la première étude qui a montré que pour un impact équivalent sur la capacité maximale de production de force, les basses fréquences de stimulation limitaient la diminution de force au cours d’une session d’électrostimulation comparativement aux hautes fréquences. L’application de manière chronique de ces protocoles lors d’un entraînement a fait l’objet de la deuxième étude. Les résultats ont montré des gains de force importants malgré les faibles intensités de stimulation et des adaptations nerveuses qui étaient dépendantes de la fréquence de stimulation. Les résultats de ces deux études ont aussi permis de mettre en évidence l’importance du phénomène d’extra force sur les adaptations induites. Ainsi, l’étude de ce dernier phénomène a fait l’objet de la troisième étude. Les résultats ont montré que lorsque le recrutement initial des UM était indirect, l’extra force était présente pour toutes les fréquences de stimulation. De plus, le développement de l'extra force a induit une diminution de l’excitabilité spinale après les basses fréquences de stimulation et une augmentation après les hautes fréquences. La dernière étude de ce travail s’est intéressée aux mécanismes expliquant ces modulations spinales. Les résultats ont montré que le mécanisme de dépression post-activation pourrait expliquer la diminution observée après les basses fréquences, tandis que ce mécanisme serait compensé par la présence de courants entrants persistants, entraînant une augmentation de l’excitabilité des motoneurones après les hautes fréquences de stimulation. L’ensemble de ces résultats souligne l’importance du retour afférent aux adaptations neuromusculaires induites après une application aiguë et chronique de l’électrostimulation<br>The aim of this thesis was to investigate the effects of electrical stimulation protocols favouring an indirect motor units’ (MU) recruitment via sensory axons activation and giving rise to extra force development, on the neuromuscular system. These protocols use wide pulse duration, low stimulation intensity, low and high stimulation frequencies and are applied over the motor nerve. The aim of the first study was to examine the effects of these protocols on the extent and origin of neuromuscular fatigue during an acute application. Results showed that for a similar impact on maximal force generating capacity, low stimulation frequencies limit force decreases during the stimulation trains as compared to high stimulation frequencies. The aim of the second study was to investigate the effects of chronic application of these protocols. Results showed important torque gains after the training period despite the low stimulation intensity used, while the induced neural adaptations were frequency-dependent. Results of these two studies also highlighted the importance of the phenomenon of extra torque on induced adaptations. Thus, the aim of the third study was to determine the conditions permitting the occurrence of extra torque, by modulating the frequency and intensity of stimulation. Main results showed that when the initial MU recruitment was mostly indirect, the developed torque was higher than the one expected for the given stimulation parameters, independently of the stimulation frequency, suggesting that the indirect MU recruitment plays a preponderant role in the occurrence of extra torque. Moreover, a frequency-dependent impact on spinal excitability was observed, resulting in a decrease after the low stimulation frequency and an increase after the high frequency. Consequently, the last study investigated the mechanisms responsible for the distinct modulation of spinal excitability. Results showed that the decrease in spinal excitability observed after the low stimulation frequency could be attributed to increased homosynaptic post-activation depression, while this latter mechanism could have been compensated by an enhanced motoneuron excitability as a result of persistent inward currents after the high stimulation frequency. All these results underline the importance of the afferent volley to the induced neuromuscular adaptations after acute and chronic electrical stimulation application
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Emerson, Nadia. "The Effects of 6-weeks of Resistance Training on the Neuromuscular Fatigue Threshold in Older Adults." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5631.
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Age-related deficits in muscle mass, strength, and function place an increased burden of work on existing skeletal muscle and may lead to early onset of neuromuscular fatigue (NMF) during activities of daily living. Resistance exercise (RE) is the proven method for improving neuromuscular function in healthy older adults. PURPOSE: To investigate the effects of 6 weeks of RE on the NMF threshold as well as strength and functional performance in older adults. METHODS: Twenty-four older adults were randomly assigned to 6 weeks of RE (EXE; n = 12; age 72 ± 6.3 y; BMI 28.4 kg/m2) or control (CONT; n = 12; age 70.3 ± 5.6 y; BMI 27.6 kg/m2). Body fat percent (BF%), lean mass (LM), and fat mass (FM) were measured using DEXA and participants performed a discontinuous cycle ergometer test, physical working capacity at fatigue threshold (PWCFT), to determine the onset of NMF. Functional performance was assessed by time to complete 5 chair rises (CHAIR) and walk an 8-foot course (WALK). Lower body strength was assessed by predicted 1-RM leg extension (1RM). Two-way Analysis of Variance (ANOVA; time [PRE, POST] x group [EXE and CONT]) and magnitude based inferences were used to compare dependent variables. RESULTS: RE significantly increased 1RM (35%; p = 0.001) and CHAIR (20%; p = 0.047). RE had a likely beneficial effect on WALK (15%) and a possibly beneficial effect on PWCFT (14%). There were no significant changes to LM or FM, however, women in EXE significantly decreased BF% (p = 0.020). CONCLUSION: Results suggest that RE improves measures of strength and functional performance and possibly the onset of NMF in older adults.<br>M.S.<br>Masters<br>Child, Family, and Community Sciences<br>Education and Human Performance<br>Sport and Exercise Science; Applied Exercise Physiology
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Morgan, P. "The effect of acute consumption of non-specific COX-inhibitors on neuromuscular fatigue and exercise performance." Thesis, University of Exeter, 2019. http://hdl.handle.net/10871/36529.
Full textAbstract:
Exercise-induced fatigue is a complex, multifactorial process, the physiological bases of which are still widely debated. Recent research has implicated pain sensation in the aetiology of exercise-induced neuromuscular fatigue. Indeed, acute consumption of acetaminophen (ACT, or paracetamol), a non-specific inhibitor of the cyclooxygenase (COX) enzymes which synthesise prostaglandins and sensitise group III/IV muscle afferents, has been shown to improve exercise performance concomitant with a lower pain and effort sensation. However, the neurophysiological bases for the potential ergogenic effect of acute ACT ingestion, and how this influences the power/torque-duration relationship, have yet to be determined. Therefore, the purpose of this thesis was to assess the effect of acute consumption of the recommended therapeutic dose (1 g of ACT and 400 mg of IBP) of common pain-relieving, COX-inhibiting medicines on performance and the mechanisms of neuromuscular fatigue development in a variety of different exercise tests. Study 1: Mean torque (61 ± 11 vs. 58 ± 14% pre-exercise MVC) and end-test torque, reflective of critical torque, (44 ± 13 vs. 40 ± 15% pre-exercise MVC) were greater in the ACT trial compared to placebo (PL) when completing 60 maximum voluntary contractions (MVCs) of the knee extensors (both P < 0.05). Voluntary activation (VA; a marker of central fatigue) and potentiated twitch (pTw; a marker of peripheral fatigue) declined at a similar rate in both conditions (both P > 0.05). However, the decline in electromyography (EMG) amplitude, a marker of muscle activation, was attenuated in the ACT trial with EMG being greater compared to PL from 210 s onwards (P < 0.05). Study 2: Compared to PL, ACT ingestion increased end-test power, reflective of critical power (ACT: 297 ± 32 vs. PL: 288 ± 31 W, P < 0.001), and total work done (ACT: 66.4 ± 6.5 vs. PL: 65.4 ± 6.4 kJ, P < 0.05) without impacting Wˈ (ACT: 13.1 ± 2.9 vs. PL: 13.6 ± 2.4 kJ, P > 0.05) or the M-wave amplitude (P > 0.05) during a 3-min all-out cycling test. EMG declined throughout the 3-min protocol in both the PL and ACT conditions; however, the decline in EMG was attenuated in the ACT condition, with the EMG amplitude being greater compared to PL over the last 60 s of the test (P < 0.05). Study 3: Time-to-exhaustion (Tlim) during severe-intensity knee extensor exercise in the right leg was 19% shorter after completing prior severe-intensity knee extensor exercise to exhaustion in the left leg following placebo ingestion (Leg2PL) compared to no prior fatigue in the left leg (Leg2CON) (Leg2CON: 385 ± 104 vs. Leg2PL: 311 ± 92 s; P < 0.05). ACT ingestion did not improve Tlim in the left leg without prior contralateral fatigue (Leg1ACT) compared to the placebo condition (Leg1PL) (Leg1CON: 396 ± 105 vs. Leg1PL: 390 ± 106 vs. Leg1ACT: 402 ± 101 s; P < 0.05). Moreover, ACT ingestion did not improve Tlim in the right leg following prior contralateral fatigue in the left leg (Leg2ACT) compared to the placebo condition (Leg2PL) (Leg2ACT: 324 ± 85 vs. Leg2PL: 311 ± 92 s; P > 0.05). There were no changes in intramuscular phosphorous substrates and metabolites, ratings of perceived exertion or EMG amplitude after ACT ingestion compared to PL ingestion in the severe-intensity single-leg knee extensor exercise tests completed with or without prior contralateral fatigue. Study 4: Mean torque (IBP: 60 ± 12 vs. PL: 58 ± 14% of pre-exercise MVC) and end-test torque (IBP: 41 ± 16 vs. PL: 40 ± 15% of pre-exercise MVC) were not different between the IBP and PL conditions when completing 60 MVCs of the knee extensors (P > 0.05). Similarly, end-test power output (IBP: 292 ± 28 W vs. PL: 288 ± 31 W) and work done (IBP: 65.9 ± 5.9 kJ vs. PL: 65.4 ± 6.4 kJ) during the 3-min all-out cycling tests were not different between the IBP and PL conditions (all P > 0.05). Neuromuscular fatigue markers developed at a similar rate in both exercise tests in the PL and IBP conditions (all P > 0.05). In conclusion, acute consumption of ACT, but not IBP, increased muscle activation and critical torque (and power), and attenuated fatigue development during maximal-intensity knee extensor and cycle ergometry exercise. However, acute ACT ingestion did not influence Tlim during continuous severe-intensity knee-extension exercise completed with or without prior fatigue of the contralateral limb. The original findings from this work suggest that acute ACT ingestion, but not IBP ingestion, might have implications for improving performance during maximal-intensity, but possibly not severe-intensity constant work rate exercise with these ergogenic effects linked to an increase in muscle activation. These findings offer insights into the potential for non-specific COX inhibitors to influence performance and neuromuscular fatigue development during different forms of exercise.
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Eladly, Ahmed Fayed. "Applicability of wireless injectable microstimulators based on volume conduction for high density neuromuscular stimulation." Doctoral thesis, Universitat Pompeu Fabra, 2021. http://hdl.handle.net/10803/671529.
Full textAbstract:
This thesis was conducted within the framework of the eAXON project that is aimed at
developing injectable wireless sub-millimetric single-channel addressable microstimulators
based on volume conduction called eAXONs that could be inserted in large numbers to
provide high density neuromuscular stimulation for restoring functional movement to
paralyzed limbs with minimal invasiveness. It is demonstrated that multi-channel
intramuscular stimulation significantly delays electrically–induced muscle fatigue, while
single-channel stimulation does not. It is shown that the nerve supply of mammalian
skeletal muscles appear to be extensively compartmentalized. Meaning, a large number of
eAXONs can be implanted, while their independence is maintained. Lastly, the eAXONs are
very thin because they act as rectifiers and perform neurostimulation by instantaneously
transforming bursts of externally applied volume conducted high frequency currents into low
frequency waveforms. Waveforms created with this approach are less current, charge,
energy efficient than square waveforms conventionally used in neurostimulation. Therefore,
with eAXONs, there is a tradeoff between device miniaturization and stimulation efficiency.
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Nanjundeswaran, (Guntupalli) Chaya D., Jessie VanSwearingen, and Katherine Verdolini Abbott. "Metabolic Mechanisms of Vocal Fatigue." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/1761.
Full textAbstract:
Objective
This study aimed to identify potential metabolic mechanisms including (1) neuromuscular inefficiency, (2) cardiovascular recovery deficits, or (3) both, in individuals with complaints of vocal fatigue.
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Bisson, Etienne. "Influence of Neuromuscular Fatigue of the Lower Limb on Postural Control and Associated Central Processes in Young and Older Adults." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23612.
Full textAbstract:
This thesis investigates the differential effects of muscle fatigue on center of pressure (COP) sway and associated central processes (attentional demands and sensory re-weighting) in older compared with young adults. More specifically, we first sought to determine whether the effect of muscle fatigue on unipedal stance was greater during a dual-task in older versus young adults, and second, to determine whether the effect of muscle fatigue on bipedal stance was greater in a condition with less reliable proprioceptive information in older versus young adults. Our main results show that with different muscle groups fatigued (ankle or hip) and postural tasks with varying difficulty (unipedal stance or bipedal stance on compliant surface), young adults increased their COP sway displacement and velocity with muscle fatigue, but not the associated attentional demands. When the central nervous system needed to increase the weight of the vestibular inputs due to sensory information being less reliable at the ankle joints from standing on a compliant surface (peripheral somatosensory information), COP sway displacement and velocity in young adults were greater with ankle muscle fatigue. We also found that healthy older adults were able to compensate for muscle fatigue just as well as young adults when visual information was available during a unipedal stance or when visual information was not available during a bipedal stance on a firm surface. However, when standing on a compliant surface, older adults showed a greater increase in COP sway displacement compared to young adults and increased attentional demands when visual information was not available during a bipedal stance. Our results suggest that healthy young and older adults are able to compensate for ankle muscle fatigue to limit postural control alterations during quiet standing under different conditions, and that the extent of postural control alterations largely depends on the tasks performed. The compensation strategies may be less efficient for older adults with less reliable proprioceptive information and without vision. Thus, a frailer group of older adults, with already reduced proprioception and/or reduced vision could possibly have more difficulty to efficiently use the same compensation strategies, and may be more at risk of falling when fatigued.
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Duan, Xu. "Influence of gender and obesity on motor performance, neuromuscular control and endurance in older adults." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/91479.
Full textAbstract:
The rapid growth of an older demographic is an increasing concern around the world. Older people have been reported to suffer from physiological and neuromuscular declines in several systems including skeletal muscles, central nervous system, cardiovascular processes and respiratory function. These age-related changes are often reflected through impairments in functional performance of occupational tasks as well as activities of daily living. This may make an older population more prone to musculoskeletal disorders and injuries. In addition, health problems and injury risks are likely amplified by factors such as obesity. Obesity has emerged as a serious health concern in the United States in recent decades. However, obesity-related changes in performance and motor control as well as how they will be modified by gender, specifically among older adults, are still largely unexplored. As motor variability has recently been reported to be associated with fatigue development and may have the potential to reveal underlying mechanisms of neuromuscular control, the main goals of this study were to investigate the influence of gender and obesity on motor performance, neuromuscular control and endurance in the elderly, by examining differences in motor variability during intermittent submaximal isometric exertions of the knee and hand.
Fifty-two older participants with age over 65 were recruited into four groups: obese male (9), obese female (13), non-obese male (15) and non-obese female (15). The obese groups consisted of those whose BMI was greater than 30 kg/m2. Participants were asked to perform intermittent (15s on and 15s off) isometric handgrip and knee extensions at 30% MVC until exhaustion. Force and muscle activations of the Vastus Lateralis, Rectus Femoris, Extensor Carpi Radialis and Flexor Carpi Radialis muscles were collected through the endurance task. Motor variability was quantified using the coefficient of variation (CV) and sample entropy (SaEn) of the surface electromyography (EMG) and force signals.
Motor variability during exercise differed both between males and females, and between obese and non-obese people, reflecting different motor strategies employed in order to prolong endurance. Overall, across all individuals, we observed a significant positive correlation between cycle-to-cycle variability of knee extensor muscle activation during the baseline period of the task and endurance time. As for gender differences, males exhibited longer endurance times than females, and seemed to achieve that through utilizing a motor strategy involving a more variable (higher CV) and less complex (lower SaEn) agonistic muscle activity. Since this was accompanied by a lower fluctuation in the force signal (lower CV) and a higher complexity of force (SaEn), we interpreted this to be a motor strategy involving more variable recruitment of synergistic and antagonistic motor units during the knee extension task to prolong endurance time, among males compared to females. As for obesity differences, there were no obesity-related changes in endurance time. However, obese individuals exhibited a greater cycle-to-cycle variability that was positively correlated with endurance time during the knee extension task, indicating a larger alteration in the recruitment of motor units across successive contractions, which contributed to comparable endurance time and performance with their non-obese counterparts. During the hand-grip tasks, variabilities in force and muscle activity followed similar trends as the knee extension task. However, there were no significant gender or obesity differences in endurance time, and there also weren't any significant correlations between any of the dependent variables with endurance time.
Thus, this study was a basic investigation into changes in motor variability and how it was associated with the development of fatigue among older adults; and the potential influences of gender and obesity on the relationships. Two tasks of high relevance to both occupational life and activities of daily living, i.e. knee extension and hand-grip were considered. Our findings enhance the theoretical understanding of the underlying neuromuscular control patterns and their relationship with fatigue for different individuals. Given that both aging and obesity rates are rising continuously and becoming a substantial health and safety problem especially in the occupational environment, the results from this study are both timely and critical for practical design applications, especially by recognizing the importance of having a variable motor pattern in task performance, even among older adults.<br>MS
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Blaisdell, Robert B. "Effects of Neuromuscular Fatigue Resulting from Repeat Sprint Exercise Among Trained Cyclists on Measures of Strength and Power Performance." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3621.
Full textAbstract:
The purpose of this dissertation is to better understand the role of repeated-sprint ability (RSA) and resulting fatigue in cyclists; how it relates to measures of aerobic power and strength and power performance indices- due to the nature of cycling competitions and the necessity of RSA for success.
The first part of this dissertation attempted to elucidate the relationship between RSA and aerobic power and strength/ power measures in competitive cyclists. The purpose was to potentially illustrate the importance of the inclusion of strength and power training in the training regimen of cyclists. The findings showed several statistically significant relationships between variables of RSA and aerobic power or the isometric squat test.
The second part of the dissertation examined the effects of fatigue induced from the acute bout of repeat sprint exercise on strength and power measures in three different recovery periods. It is commonplace for cyclists to have several heats in one day of racing. Examining the effects of fatigue on strength measures such as peak force and rate of force development could begin to delineate how an individual experiences fatigue based on their own characteristics, enabling them to design a training program to address these strengths/ weaknesses to optimize performance and decrease fatigue. The results from a repeated measures analysis of variance found no statistically significant effect on PF or RFD. Additional comparisons showed moderate effects of fatigue on RFD throughout the three post-RSE trials. There was also a moderate correlation between the RSE fatigue % decrement score and the isometric RFD fatigue % decrement score.
What we may conclude from this dissertation is that fatigue has various causes and can vary with an individuals’ unique physiology and how they respond to performance variables on any specific day can vary. Development of increased strength and subsequent power, or “explosive strength”, may have advantages in competitive cycling. Coupling proper strength and power training with an aerobic training regimen, may greatly benefit the athlete by increasing their peak power output, economy of movement, delaying fatigue, improving anaerobic capacity, and overall enhancing their maximal speed.
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Botelho, André Luís. "Avaliação da fadiga neuromuscular por meio da análise de frequência do sinal eletromiográfico de sujeitos controle e pacientes acometidos por disfunção temporomandibular tratados com placa oclusal resiliente e rígida." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/58/58133/tde-22052012-155242/.
Full textAbstract:
A incapacidade de produzir repetidamente no tempo um determinado nível de força ou potência muscular designa-se por fadiga neuromuscular. A etiologia da fadiga muscular tem atraído o interesse de pesquisadores há mais de um século. Contudo, os seus agentes e locais definitivos permanecem ainda por serem identificados. Este trabalho teve por objetivo avaliar a fadiga neuromuscular por meio da análise de frequência do sinal eletromiográfico dos músculos masseter e temporal anterior de ambos os lados em 3 grupos distintos: sujeitos saudáveis assintomáticos para disfunção temporomandibular (DTM), pacientes acometidos por DTM tratados com placa oclusal resiliente e pacientes acometidos por DTM tratados com placa oclusal rígida. Para isso, participaram da pesquisa 100 sujeitos assintomáticos para DTM e 30 pacientes com DTM subdivididos em 2 grupos: tratados com placa rígida tipo FARC; e tratados com placa resiliente. Todos realizaram exame eletromiográfico antes e após o tratamento com placa oclusal. Os resultados demonstraram que houve diferenças estatisticamente significantes na comparação da taxa de fadiga avaliada antes e após o tratamento com placa oclusal, tanto para o grupo Placa FARC como para o grupo Placa Soft. Houve diminuição da taxa de fadiga após o tratamento com placa para os músculos masseter esquerdo e temporal anterior direito para o grupo Placa Soft; e diminuição da taxa de fadiga após o tratamento para o músculo temporal anterior esquerdo para o grupo Placa FARC. Pode-se concluir que o tratamento com ambos tipos de placa oclusal foi eficiente na redução da taxa de fadiga neuromuscular em pacientes acometidos por DTM.<br>The repeated failure to produce in time a certain level of strength or muscle power is called neuromuscular fatigue. The etiology of muscle fatigue has attracted the interest of researchers for over a century. However, their agents and local definitive remain yet to be identified. This work aimed to evaluate neuromuscular fatigue by frequency analysis of the electromyographic signal of the masseter and anterior temporal muscles of both sides in three different groups: healthy subjects asymptomatic for temporomandibular disorders (TMD), patients suffering from TMD treated with resilient occlusal splint and patients suffering from TMD treated with rigid occlusal splint. For this, 100 subjects asymptomatic for TMD participated in the survey and 30 patients with TMD subdivided into 2 groups: treated with rigid splint type FARC, and treated with resilient splint. All electromyographic examinations performed before and after treatment with occlusal splint. The results showed that statistically significant differences when comparing the rate of fatigue assessed before and after treatment with occlusal appliance, for both groups. There was a decrease in the rate of fatigue after treatment with occlusal splint to the left masseter and right anterior temporal in the group Soft Splint; and decrease in the rate of fatigue after treatment for left anterior temporal muscle to the group FARC Splint. It can be concluded that treatment with both types of occlusal splint was effective in reducing the rate of neuromuscular fatigue in patients affected by TMD.
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Giandolini, Marlène. "Gestion de l'impact et de la fatigue neuromusculaire en trail running." Thesis, Saint-Etienne, 2015. http://www.theses.fr/2015STET009T/document.
Full textAbstract:
Bien que constitué anatomiquement et physiologiquement pour la course d’endurance, l’Homme est considérablement exposés à diverses blessures musculo-squelettiques liées à la répétition de contraintes mécaniques. Le coureur de trail running par exemple est soumis à de nombreux impacts ainsi qu’à une fatigue et des dommages musculaires sévères. Ces chocs répétitifs et dommages musculaires réduiraient la tolérance du coureur face aux contraintes mécaniques le poussant ainsi à altérer sa cinématique de course. Par conséquent, minimiser les dommages musculo-squelettiques serait déterminant pour la performance en trail running. Des évidences montrent que la pose de pied altère la localisation et l’intensité des contraintes appliquées au système musculo-squelettique. L’objectif de ce travail de thèse a été d’étudier l’influence du pattern de pose de pied sur l’impact et la fatigue neuromusculaire en trail running. Les phases de descente ont été tout particulièrement étudiées du fait qu’elles sont les plus traumatisantes. En effet, ce travail de thèse a mis en évidence qu’en situation de trail running, l’intensité de l’impact augmente lorsque la pente diminue, et que la fatigue neuromusculaire périphérique est aussi sévère à la suite d’une descente isolée qu’après un ultra-trail de plusieurs heures. En étudiant l’influence de la pose de pied adoptée au cours d’une descente en situation de trail running, il a été observé qu’attaquer le sol par l’avant du pied augmentait la fatigue neuromusculaire aux extenseurs du genou. Cependant, une importante variabilité dans les patterns de pose de pied adoptés au cours de la descente a été associée à une baisse de la fatigue neuromusculaire aux extenseurs du genou et fléchisseurs plantaires. L’influence de la pose de pied sur l’intensité du choc et le contenu vibratoire le long des axes axial et transversal a également été démontrée : adopter une attaque talon diminue la sévérité du choc axial mais réduit l’intensité du choc transversal. La principale conclusion est qu’aucun pattern de course ne saurait être universellement recommandé du fait que « changer de pose de pied » est synonyme de « changer la localisation et la magnitude des contraintes appliquées au système musculo-squelettique ». En ce sens, alterner entre différents patterns de course serait une stratégie efficiente en trail running<br>Although Humans are “born” anatomically and physiologically adapted to long distances run, they are substantially exposed to various musculoskeletal overuse injuries. Trail runners sustain a high number of foot-to-ground contacts and develop severe muscle fatigue and damages. Repetitive shocks and muscle damages would reduce the runners’ tolerance to mechanical strains leading to changes in running kinematics. Minimizing musculoskeletal damages is therefore considered paramount for performance in trail running. Numerous studies highlighted that the foot strike pattern alters the localization and magnitude of the mechanical strains applied on the musculoskeletal system. The main purpose of this thesis was to study the influence of the foot strike pattern on impact and neuromuscular fatigue in trail running. Downhill sections were mainly investigated since they are the most mechanically stressful. Indeed, it was observed from this thesis’ work that, in real trail running practice, the impact intensity increases as the slope decreases, and that the neuromuscular fatigue induced by a single downhill run is as severe as the one induced by an ultratrail race that lasts several hours. Investigating the effect of the foot strike pattern adopted during a downhill trail run on fatigue, it was observed that forefoot striking increases the neuromuscular fatigue at knee extensors. However, a high variability in foot strike patterns adopted was associated to a lower neuromuscular fatigue at both knee extensors and plantar flexors. The effect of the foot strike pattern on axial and transversal shock and vibration content was also demonstrated: heel striking was correlated to a lower impact severity along the axial axis of the skeleton but a greater one along its transversal axis. The main conclusion of this thesis is that no single foot strike pattern should be universally advised due to “changing of foot strike” means “changing the localization and magnitude of the mechanical stress applied on the musculoskeletal system”. Switching between different running patterns might be an efficient strategy in trail running
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Brandon, Raphael. "Investigations of the neuromuscular response during and following elite maximum strength and power type resistance exercise." Thesis, University of Stirling, 2011. http://hdl.handle.net/1893/3655.
Full textAbstract:
The thesis aimed to analyse the acute neuromuscular (NM) response during and following maximum strength and power training methods. The primary aim of study one was to establish the reliability of biomechanical and surface electromyographic (sEMG) measurements during barbell squat exercise. This would enable the subsequent studies to precisely assess muscle activity and mechanical power during barbell resistance exercise sessions. Nine male well-trained subjects performed squat exercise on three separate trial days. Each trial comprised one set of squat at 50, 75 and 100% of 3RM load. Synchronous recordings of knee joint kinematics from a flexible electrogoniometer, barbell displacement from a single linear position transducer and quadriceps sEMG amplitude were made. The mean maximum knee angle during squat was recorded at each load, and the overall inter-trial coefficient of variation (CV) was 5.5%. Mean concentric repetition power was processed from displacement data and derived into force and velocity values. The overall inter-trial CV for mean power was found to be 8.4%. The raw sEMG signal was processed into root mean square (RMS) amplitude and normalised to values taken from pre-trial knee extension maximum voluntary contractions (MVC). RMS amplitude was processed for the whole concentric phase and a 200 ms time interval at a knee angle of 70°, which matched the knee angle used during MVC. Inter-trial CV for RMS amplitude from the concentric phase and 70° knee angle were 7.2% and 16.4% respectively. There were no differences in RMS amplitude, maximum knee angle or mean power across trial days. It was concluded there was acceptable reliability for all three measurements (CV < 10%), if RMS amplitude was processed from the concentric phase. Based upon the measurement reliability, the analysis system was considered suitable for monitoring power and sEMG during barbell exercise. The second study aimed to establish the reliability of muscle fibre conduction velocity (MFCV) measurements during barbell squat. This was of interest, as MFCV may provide useful information of NM recruitment and fatigue processes during resistance exercise. The study was also used as a preliminary investigation of MFCV response, in comparison to RMS amplitude, to increasing fatigue and load during squat exercise. Nine well-trained male subjects performed a series of exercises on two separate trial days. Each trial comprised isometric knee extensions at 50, 75 and 100% of MVC force, followed by barbell squats at 50, 75 and 100% of 3RM, and then a maximal bout of squat jumps at 50% 3RM load, performed until failure. sEMG measurements were recorded from a four-electrode array, secured upon the vastus lateralis. Normalised RMS amplitude was processed as above, and MFCV was processed from the inter-electrode distance and time delay between two double differentiated and correlated signals, using bespoke software. The overall value of MFCV during squat was 5.8 m.s-1. The inter-trial CV for MFCV was 9.6% during squat and 12.1% during squat jump. Based upon acceptable reliability of 10%, MFCV measurements from barbell squats were considered reliable. As expected, MFCV significantly increased with each knee extension force level (4.7 ± 1.4, 5.6 ± 1.5 and 6.2 ± 1.8 m.s-1) (p<0.01), along with RMS amplitude (p<0.0001). No differences in MFCV were found between squat loads, whilst RMS amplitude significantly increased with load (p<0.0001). Power (1920 ± 143 versus 1407 ± 254 W) and MFCV (5.7 ± 1.4 versus 4.6 ± 1.0 m.s-1) significant decreased (p<0.001) from the start to the end of the squat jump trial, with RMS amplitude unchanged. Therefore, MFCV altered with increasing fatigue, but not load, during dynamic squat exercise. It was concluded that MFCV provides useful and reliable data for acute fatigue investigations of barbell resistance exercise, in addition to sEMG amplitude measures. The following three investigations compared NM responses during and following maximum strength and power type resistance exercise sessions with different exercises, loads and movement speeds. The sessions were designed to represent elite athlete training practices, to help inform the optimisation of resistance exercise programmes. The first of these studies aimed to compare NM response to a typical maximum strength session performed with barbell squat or deadlift exercise. The purpose was to assess if technical differences between the exercises, influenced the acute NM response. Nine elite trained weightlifters performed the trial sessions of five sets of five repetitions on separate days. Normalised RMS amplitude, MFCV and power was continually measured during exercise repetitions, using the methods established above. NM function was assessed pre- and post- sessions using MVC force, central activation ratio (CAR) from superimposed stimulation during MVC, and jump performance (CMJ). The exercises were performed with subjectively matched load levels, corresponding to active muscle RPE = 17 (Borg scale), and also with controlled lifting speed. However, the squat load was lowered and raised upon the lifter’s back, whilst deadlift load was grasped in the hands, raised from the floor and then dropped. Repetition mean power was unchanged within and across sets of both sessions. Repetition RMS amplitude significantly increased (p<0.001) within sets of squat and deadlift, whilst a significant interaction between sessions and set (p<0.001) demonstrated RMS increased more during squat. Furthermore, a significant reduction in repetition MFCV was found within sets of squat (p = 0.034), but not deadlift. This suggests that motor unit activation increased during both exercises, as a response to the task of maintaining power during repetitions of whole body lifting. However, acute fatigue within squat sets led to additional increased activation as a NM compensation strategy. No pre- versus post- session differences were found for MVC, CAR or CMJ; suggesting minimal change in NM function occurred following five sets of maximum strength type resistance exercise, in well-trained subjects. The primary aim of the second study was to compare NM response and 24-hour recovery following barbell exercise maximum strength and power type sessions. The purpose was to specifically establish the degree and nature of NM response, as previous findings were unclear and barbell exercise sessions of this type have not been compared. 10 elite sprint athletes performed sessions comprising squat, split squat and push press, with four sets x repetitions per exercise. The maximum strength session exercises involved loads corresponding to active muscle RPE = 17 (Borg scale) and metronome controlled movements. The power session exercises used 30% of the maximum strength barbell load, performed as fast as possible. Repetition sEMG and power was monitored throughout each session, as above. NM function was assessed, pre-, post- and 24-hour post- each session, using the same tests as above. However, evoked peak twitch force (Pt) was also included to the pre- and post- assessments. Overall, the maximum strength session involved greater total work (p = 0.008), but lower mean power during exercise repetitions (p<0.001) in comparison to the power session. MVC and Pt force values both significantly decreased (p<0.05) pre- versus post- both sessions. However, MVC reduced more following maximum strength session (p<0.01). CAR and CMJ were unchanged post-both sessions and no differences were found between pre and 24-hour post session NM tests. The decreased Pt but not CAR findings, suggest peripheral fatigue explains the reduced force generation capacity following maximum strength and power sessions, contrary to previous resistance exercise session findings. Up to 24-hours may be required to recover force generation capacity following this volume of resistance exercise.
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Torrado, Pineda Priscila. "Valoración de la fatiga neuromuscular en el antebrazo del motorista de velocidad." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/311797.
Full textAbstract:
Actualmente, es frecuente ver cómo muchas escuderías tienen sus motos paradas en boxes por patologías neuromusculares de sus pilotos oficiales, debiendo recurrir a pilotos substitutos. Durante una carrera de motos la fatiga es alta porque los pilotos tienen que soportar niveles de tensión muscular elevados, particularmente en los brazos y antebrazos y además mantenidos durante un largo periodo de tiempo.
Un estudio previo realizado durante una carrera de resistencia de 24 h (Marina, Porta, Vallejo, & Angulo, 2011) sugirió que el sistema central no era el motivo principal que explicaba la disminución en la contracción máxima voluntaria (CMV), sino factores periféricos. De ese estudio surgió la necesidad de simular la posición del piloto durante la frenada, así como proponer un protocolo estandarizado en un entorno controlado, dando lugar a la presente tesis.
En el primer estudio comparamos dos protocolos, uno continua y otro intermitente (PIF) modificado a partir del estudio surgido de las 24 h. El incremento de la amplitud electromiográfica (EMG) y el decremento de la frecuencia EMG confirmaron mediante el protocolo continua los resultados obtenidos por autores anteriores, pero no con el PIF. Nuestro PIF se mostr6 mas discriminativo entre pilotos expertos y grupo control, alcanzando los primeros una duración mayor y verificándose una mayor correlación con las molestias en el antebrazo. El segundo estudio examin6 el comportamiento de la serial EMG combinando diferentes intensidades y tiempos de descanso, con el sujeto en posición de pilotaje accionando la maneta de freno con la mano derecha. El objetivo de este estudio era verificar si la disparidad de los resultados EMG en PIFs publicados en la literatura, puede deberse a diferentes duraciones en los periodos de contracción-relajación, así como a las intensidades de contracción (% CMV). Los resultados sugirieron que utilizar intensidades bajas (-30 % CMV) y tiempos de recuperación cortos de no más de 10 segundos es la mejor estrategia para inducir fatiga neuromuscular.
El tercer estudio nació de la idea que posiblemente no todo el mundo tiene el mismo patrón de disminución de la CMV a lo largo del tiempo. Desarrollamos un modelo matemático no lineal que permitiese verificar dicha hipótesis. Después de aplicar dicho modelo confirmamos que efectivamente, podríamos distinguir tres perfiles básicos de fatiga funcional (lineal, exponencial y tres fases), valorada a lo largo de un PIF a través de la medición repetitiva de la CMV. Sabiendo que las mejores pilotos presentaban un patrón lineal, este segundo estudio supone un primer paso para estudiar si una determinada preparación física podría cambiar y/u optimizar un patrón inicial hacia uno lineal.
De la sucesión de estudios descritos anteriormente, vimos que para progresar en esta línea de investigación teníamos que combinar las contracciones voluntarias y la serial EMG con la valoración de otros marcadores neurofisiológicos de fatiga central y periférica. Por eso en el cuarto estudio aplicamos potenciales evocados mediante estimulación eléctrica periférica y estimulación magnética transcraneal, en el segmento fatigado (derecho) y no fatigado (izquierdo), para estudiar posibles efectos contralaterales de la fatiga durante la recuperación del PIF. En esta nueva versión de protocolo modificamos los tiempos de descanso y añadimos el gesto de girar el puño del gas, para acercarnos más a la situación real de pilotaje. Los resultados obtenidos en este último estudio y en el conjunto de la tesis sugieren que la fatiga experimentada par las motoristas se debe principalmente a factores periféricos. Sin embargo no podemos descartar factores centrales.<br>During a motorcycle race fatigue levels are high as riders are required to endure high levels of muscle tension for long periods of time, especially in their arms and forearms. For this reason the present thesis focuses on fatigue in the right forearm muscles.
In the first study we compared an intermittent fatigue protocol (IFP) especially designed for motorcycle riders with a continuous protocol. The IFP was not only able to discriminate between the riders and the control group, but also proved to have a strong relationship with the level of motorcyclist forearm discomfort. Despite the results obtained with continuous protocol were similar to those reported in the literature, our IFP confirmed the discrepancies between studies suggesting that the combination of different, contraction-relaxation periods, submaximal contraction intensities (% maximal voluntary contraction, MVC), muscle groups and other non-controlled or non-reported factors, are critical to understand muscle fatigue in IFPs. The above mentioned results invited us to investigate the effects of two different recovery periods and two intensities on the EMG signal in the study II, using a unique IFP. The results suggested that using short recovery periods and low intensities is the best approach to evoke fatigue. In study Ill, time course parameters of contraction and relaxation were examined to better characterize the reduction in the maximal force generating capacity of a muscle (MVC) during an IFP specifically designed for road racing motorcycle riders. Also, a mathematical nonlinear force fatigue model was proposed and confirmed a satisfactory adjustment to all participants. The same mathematical expression derived three patterns of force fatigue : three-phase , exponential and linear. Finally, in the fourth study which purpose was to investigate the contribution of central and peripheral mechanisms of fatigue on the exerted and contralateral extensor digitorum communis following an IFP, we examined the time-course of recovery of maximal voluntary contraction (MVC), compound muscle action potential (CMAP), motor evoked potential (MEP) to transcranial magnetic stimuli and the cortical silent period (CSP) throughout 20 min of recovery. The results suggested that local factors were those mainly responsible for the incomplete MVC recovery after the IFP.
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Souissi, Hiba. "Altération des stratégies musculaires chez des patients post-AVC : conséquences sur la marche et en condition de fatigue." Thesis, Côte d'Azur, 2018. http://www.theses.fr/2018AZUR4213/document.
Full textAbstract:
L'hémiparésie est une des déficiences fréquemment observée après un accident vasculaire cérébral (AVC). Elle s’accompagne d’une gestion anormale de la co-contraction musculaire et des déficits de production de force qui contribuent de manière significative à réduire la performance de la marche. Une réorganisation des stratégies musculaires est mise en place pour répondre aux contraintes de stabilité et de propulsion du centre de masse au cours de la marche. Cependant, la littérature reporte très peu de données sur les actions musculaires des membres, parétique et non-parétique, au cours de la marche. De plus, les patterns de co-contraction ont été évalués à partir des seules données EMG chez les patients post-AVC. Par ailleurs, les patients post-AVC présentent une fatigabilité plus importante que les individus sains. Alors que plusieurs facteurs sont impliqués dans la fatigue, le rôle de la co-contraction reste mal connu. L’objectif principal de ce travail était de caractériser les altérations des stratégies musculaires des membres inférieurs chez des patients hémiparétiques post-AVC au cours de la marche et lors de la fatigue induite par des contractions maximales volontaires concentriques isocinétiques. Ce travail introduit l'utilisation novatrice d'une modélisation neuromusculo-squelettique assistée par EMG pour estimer les forces musculaires générées autour des articulations du genou et de la cheville au cours de la marche chez des patients post-AVC. De plus, nous avons montré qu’une quantification de la co-contraction à partir des moments musculaires est préférable par rapport à des mesures EMG. Les résultats ont montré que les forces réduites développées par les fléchisseurs plantaires de la cheville et les extenseurs du genou du côté parétique seraient à l’origine des troubles de la marche hémiparétique. Les forces musculaires élevées produites par les quadriceps et les fléchisseurs du genou du côté nonparétique, ainsi que la force élevée générée par les fléchisseurs du genou du côté parétique, par rapport aux sujets sains, pendant la phase d’appui correspondrait à une réorganisation comportementale, permettant d’augmenter la stabilité et d’ajuster la propulsion du centre de masse. Cette réorganisation des patterns de coordination musculaire se manifeste également par des niveaux élevés de co-contraction (basée sur les moments musculaires) observés du côté parétique et non-parétique au cours de la marche. Il s’agit d’une stratégie d'adaptation permettant d’améliorer la stabilité articulaire. Cependant, la cocontraction plus élevée au cours de la marche peut contribuer à l’augmentation du coût énergétique chez les patients et entraîner une fatigue plus rapide. L’étude de la fatigue neuromusculaire chez les patients post-AVC a mis en évidence une fatigabilité moindre par rapport aux sujets sains en présence d’un niveau plus élevé de co-contraction (basée sur les données EMG). Le déclin de l’activité EMG agoniste lors de contractions concentriques répétées, s’est produit parallèlement à un déclin de l’activité EMG antagoniste diminuant la force d’opposition au mouvement et entraînant une moindre diminution du moment net. Ceci semble être un mécanisme potentiel par lequel la production du moment net est préservée chez les patients post-AVC qui sont intrinsèquement plus faibles. Les résultats de ce travail soulignent l’importance de développer des programmes de rééducation centrés sur le renforcement des fléchisseurs plantaires et des extenseurs du genou et sur la sélectivité du contrôle des mouvements tel que l’entraînement en puissance<br>Hemiparesis is one of the most frequent deficits after stroke. It is accompanied by an abnormal muscle co-contraction pattern and an altered force production that significantly contribute to reduced gait performance. These alterations lead to a reorganization of muscle coordination patterns to ensure stability and adjust the propulsion of the center of mass during walking. However, less is known about muscle actions in the paretic and non-paretic lower limbs during walking. In addition, co-contraction patterns were evaluated from only EMG data in post-stroke patients. Furthermore, post-stroke patients manifest higher levels of fatigability than healthy individuals. While several factors are involved in fatigue, the role of co-contraction remains poorly understood. The main objective of this thesis was to characterize the alterations of the muscle strategies of the lower limbs in post-stroke hemiparetic patients during walking and during fatigue induced by isokinetic concentric maximal contractions. This thesis introduces the novel use of an EMG-driven modelling approach to measure muscle forces generated around the knee and ankle joints of the paretic and non-paretic lower limbs during gait in post-stroke patients. In addition, we have shown that quantification of co-contraction from muscle moments is preferable compared to EMG measurements. The results showed that the reduced forces exerted by the plantar-flexors and the knee-extensors on the paretic side, gives a possible explanation for hemiparetic gait abnormalities. Increased forces generated by the knee-flexor and knee-extensor muscles on the non-paretic side, as well as increased force generated by the knee flexors on the paretic side, compared to healthy subjects, during the stance phase would be a behavioral reorganization to better support body weight and properly adjust the forward center of mass. This reorganization of muscle coordination patterns is also reflected by the increased levels of co-contraction (based on muscle moments) observed on the paretic and non-paretic side during walking. This seems to be an adaptive, compensatory strategy to ensure postural stability. However, increased co-contraction during walking can contribute to an increased energy cost in patients and lead to a more rapid fatigue development. The study of neuromuscular fatigue in post-stroke patients showed less fatigability compared to healthy subjects, in the presence of a higher level of co-contraction (based on EMG data). Decreasing agonist EMG during repeated concetric contractions, occurred in parallel with decreasing antagonist EMG, reducing the relative opposing force and resulting in a less decline in net torque. This seems to be a potential mechanism by which net torque output is preserved in post-stroke patients who are inherently weaker. The results of these studies underline the importance of developing rehabilitation programs focused on the strengthening of plantar flexors and knee extensors and on the selectivity of movement control, such as power training
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CERQUEIRA, Mikhail Santos. "Exercício de preensão manual isométrico intermitente associado a diferentes níveis de compreensão vascular externa: efeitos agudos na reposta neuromuscular." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18734.
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Previous issue date: 2016-06-16<br>CAPES<br>Introdução: Exercícios de baixa intensidade executados até a falha podem gerar
hipertrofia e aumento de força muscular, porém o tempo até a falha (TF) pode ser
muito prolongado e consequentemente gerar sobrecarga articular, sendo a restrição
do fluxo sanguíneo (RFS) uma alternativa para reduzir o TF durante o exercício. A
fadiga neuromuscular após o exercício pode ser indicada por uma redução na
capacidade de produzir força e por alterações no sinal de eletromiografia (EMG),
entretanto poucos estudos têm analisado essas variáveis após o exercício com RFS
realizado até a falha. Objetivo: Verificar os efeitos de diferentes níveis de RFS
aplicados durante um exercício de preensão manual isométrico intermitente (EPMII)
no TF, na recuperação da força isométrica voluntária máxima (FIVM), da frequência
mediana (EMGFmed) e do pico do sinal de EMG bruto (EMGpico) após a falha.
Métodos: Treze homens (21 ± 1,71 anos) realizaram o EPMII com 45% da FIVM até
a falha com diferentes níveis de fluxo sanguíneo: oclusão total (OT), oclusão parcial
(OP) e fluxo livre (FL). A pressão de oclusão foi determinada em repouso de forma
individualizada. O TF foi avaliado durante o exercício. A FIVM, a EMGFmed e o
EMGpico foram mensurados antes e nos minutos 1, 3, 5, 7, 9 e 11 depois do
exercício. Resultados: O TF foi diferente (p<0,01) entre todas as situações
investigadas: OT (150 ± 68 segundos), OP (390 ± 210 segundos) e FL (510 ± 240
segundos). A FIVM permaneceu reduzida onze minutos após a falha em todas as
situações (p=0,001). Houve uma maior redução de força um minuto após a falha nas
situações OP (-45,8%; p=0,001) e FL (-39,9%; p=0,005) em comparação à OT (28,1%).
Após onze minutos de recuperação apenas na situação OP (-30,2%;
p=0,004) a força foi menor que na situação OT (-21,7%). A situação OP gerou uma
maior redução da EMGFmed nos minutos pós 5 (p=0,012) e pós 9 (p=0,034) em
comparação à OT e maior elevação do EMGpico em relação a OT (p=0,008) e FL
(p=0,034) após 7 e 9 minutos. Conclusões: Maiores níveis de oclusão vascular
resultam em menor TF, exercícios com maior duração induzem maior redução de
força após a falha e a aplicação de OP durante EPMII parece gerar maior fadiga
neuromuscular.<br>Introduction: Low intensity exercises performed to failure can increased muscle
strength and hypertrophy, but the time to failure (TF) can be very long and
consequently generate joint overload. The blood flow restriction (BFR) can be an
alternative to reduce the TF during exercise. Neuromuscular fatigue after exercise
may be indicated by a reduction in the ability to produce force and changes in the
electromyographic (EMG) signal, but few studies have examined these variables
after exercise with BFR performed to failure. Objective: To investigate the effects of
different vascular occlusion levels applied during intermittent isometric handgrip
exercise (IIHE) in time to task failure (TF), recovery of maximum voluntary isometric
force (MVIF), median frequency (EMGFmed) and peak raw EMG signal (EMGpeak) after
failure. Methods: Thirteen men (21 ± 1,71 years) underwent IIHE with 45% of MVIF
to failure with different levels of blood flow: total occlusion (TO), partial occlusion
(PO) and free flow (FF). Occlusion pressure was determined individually at rest. The
TF was evaluated during exercise. The MVIF, EMGFmed and EMGpeak were measured
before and 1, 3, 5, 7, 9 and 11 minutes after exercise. Results: The TF was
significantly different (p<0,01) among all investigated conditions: OT (150 ± 68
seconds), OP (390 ± 210 seconds) and FL (510 ± 240 seconds). The MVIF remained
low eleven minutes after failure in all conditions (p=0,01). There was a greater
reduction in force one minute after the failure in the situations PO (-45,8%;
p=0,001) and FF (-39,9%; p=0,005) compared to TO (-28,1%). After eleven minutes
of recovery only in the situation PO (-30,2%; p=0,004), the strength was lower than in
the TO situation (-21,7%). The PO situation led to a greater reduction in EMGFmed
after 5 (p=0,012) and 9 (p=0,034) minutes compared to TO and highest elevation of
EMGpeak in relation to TO (p=0,008) and FF (p=0,034) after 7 and 9 minutes.
Conclusions: Largest vascular occlusion levels result in lower TF, exercises lasting
longer induce greater reduction of strength after the failure and the use of PO during
IIHE seems to generate greater neuromuscular fatigue.
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Cavalcante, Marcos David da Silva. "Efeitos da execução prévia do exercício físico e cognitivo sobre a estratégia de prova no ciclismo: um estudo acerca dos componentes centrais e periféricos da fadiga neuromuscular." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/39/39132/tde-15072016-095944/.
Full textAbstract:
O objetivo do presente estudo foi analisar os efeitos da execução prévia de exercício físico e cognitivo sobre os componentes central e periférico da fadiga neuromuscular durante um teste contrarrelógio de 4 km de ciclismo. Para tanto, oito ciclistas treinados (n = 8) participaram de três diferentes estudos. No estudo 1, os atletas realizaram o teste contrarrelógio após assistir documentário (CON) ou após tarefa cognitiva (TC). No estudo 2, o teste de 4 km de ciclismo foi realizado após 100 drop jumps (DJ), 48 horas após 100 drop jumps (48h-DJ) e sem a realização prévia de exercício (CON). No estudo 3, o teste contrarrelógio foi realizado após fadiga prévia de membros superiores (FB) e inferiores (FP) e sem fadiga prévia (CON). Em todos os estudos, parâmetros de fadiga central e periférica foram avaliados por meio da técnica de estimulação elétrica no nervo femoral em repouso, pré e pós 4km de ciclismo. Estudo 1: O desempenho foi similar (P> 0,05) entre CON (376 ± 26,9 s) e TC (376,3 ± 26 s). Do mesmo modo, não encontramos diferenças significativas (P> 0,05) para parâmetros de fadiga central e periférica entre CON e TC. Estudo 2. O desempenho foi significativamente (P< 0,05) prejudicado em DJ (-2,3%) e houve uma tendência em 48h-DJ (-1,8%). A redução no desempenho em 48h-DJ foi devido à menor potência na parte inicial da prova (P< 0,05). Em DJ a piora no desempenho foi em decorrência de menor potência (P< 0,05) na parte inicial e final da prova. Houve uma exacerbada (P< 0,05) fadiga periférica após o contrarrelógio em DJ (1Hzpot= -44,7%) comparado com CON (1Hzpot= -20,1%). Além disso, significante fadiga de baixa frequência foi observada em DJ comparado com CON. Por outro lado, parâmetros de fadiga central e periférica apresentaram valores similares entre CON e 48h-DJ (P> 0,05). No entanto, foi encontrado aumento significativo (P< 0,05) na dor muscular tardia em 48hDJ comparado com CON e DJ. Estudo 3: O desempenho foi reduzido em FP (-2,3%) e FB (-1,5%) quando comparado com CON. O menor desempenho nas condições FP e FB foi acompanhado por redução na potência (P< 0,05) na parte inicial (condição FP) e na parte final (condições FP e FB) a prova. Ao final dos 4 km de ciclismo, os participantes apresentaram menor (P< 0,05) fadiga periférica em FB (1Hzpot= -11,9%) comparado com CON (1Hzpot= -20,1%). Em FP, houve maior fadiga periférica em comparação a condição CON e FB. Em conclusão, os resultados destes estudos sugerem que apenas a execução prévia de exercício envolvendo a musculatura utilizada no ciclismo promove alterações nos componentes periféricos da fadiga neuromuscular após 4 km de ciclismo<br>The aim of this study was to analyze the effects of previous execution of physical exercise and cognitive on the central and peripheral components of the neuromuscular fatigue during a 4 km cycling time trial. Eight trained cyclists (n = 8) participated of three different studies. In study 1, the athletes performed the 4 km cycling time trial test after watching a documentary (CON) or after a cognitive task (CT). In study 2, the 4-km cycling test was performed after 100 drop jumps (DJ), 48 hours after 100 drop jumps (48h-DJ) and without previous exercise (CON). In study 3, the time trial was performed after pre-fatigue of the upper (FU) and lower (FL) body and without prefatigue (CON). In all studies, central and peripheral fatigue parameters were evaluated via electrical stimulation in femoral nerve at rest, before and after 4km cycling. Study 1: Performance was similar (P> 0.05) between CON (376 ± 26.9 s) and TC (376.3 ± 26 s). Likewise, we found no significant differences (P> 0.05) for parameters of central and peripheral fatigue between CON and CT. Study 2: Performance was significantly (P< 0.05) impaired in DJ (-2.3%) and there was a trend in 48h-DJ (-1.8%). This reduction in performance in 48h-DJ was due to a lower power at first part of the time trial (P< 0.05). In DJ condition, loss in performance was due to lower power (P< 0.05) at the start and end phases of the test. There was exacerbated (P <0.05) peripheral fatigue after the time trial in DJ (1Hzpot = -44.7%) compared to CON (1Hzpot = 20.1%). Furthermore, a significant low frequency fatigue was observed in DJ compared to CON. On the other hand, central and peripheral fatigue parameters showed similar values between CON and 48h-DJ (P> 0.05). However, a significant increase in delayed onset muscle soreness was found in 48h-DJ than CON and DJ. Study 3: Performance was reduced in FU (-2.3%) and FL (-1.5%) compared to CON. The lowest performance was accompanied by a reduction in power (P< 0.05) in the initial (FL) and final (FL and FU phases of the time trial. After 4 km cycling, participants had a lower (P< 0.05) peripheral fatigue in FU (1Hzpot = -11.9%) compared with CON (1Hzpot = -20.1%). In FL, there was a greater peripheral fatigue compared to CON and FB condition. In conclusion, the results of these studies suggest that only the previous execution of exercise involving the muscles used in cycling causes changes in the peripheral components of the neuromuscular fatigue after 4 km of cycling
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Doix, Aude-Clémence. "Stratégies d’activation neuromusculaires de la fatigue musculaire volontairement et électriquement induite : mécanismes sous-jacents et implications cliniques." Thesis, Nice, 2013. http://www.theses.fr/2013NICE4098/document.
Full textAbstract:
La prise en charge thérapeutique de la fatigue musculaire par le biais d’exercices physiques vise à améliorer la qualité de vie et implique habituellement des exercices unilatéraux ou l’électrostimulation neuromusculaire pour compenser une fonction musculaire altérée aussi bien chez les personnes saines ou dites vulnérables (e.g. atteintes d’une pathologie ou d’un traumatisme). La fatigue musculaire est une réduction de la capacité de production maximale de force, induite par l’exercice, que la tâche puisse être maintenue ou non (Bigland-Ritchie et al. 1983; Gandevia 2001; Enoka and Duchateau 2008). L’objectif général de cette thèse était d’étudier les stratégies d’activation neuromusculaire lors de la fatigue musculaire, de l’endurance musculaire et sur la performance musculaire au cours et/ou après des contractions volontaires et évoquées électriquement chez des personnes saines ou vulnérables tels que des enfants atteints d’infirmité motrice cérébrale (IMC) et des patients atteints de dystrophie musculaire facio-scapulo-humérale (DMFSH)<br>The clinical care of muscle fatigue with exercise therapies aim at quality of life improvement and usually involve unilateral exercises or neuromuscular electrical stimulation to compensate impaired muscle function in both healthy and health-compromised people. Muscle fatigue is a decline in maximal force production, induced with exercising, whether or not the task can be maintained (Bigland-Ritchie et al. 1983a; Gandevia 2001a; Enoka and Duchateau 2008). The overall objective of this thesis was to study the effect of neuromuscular activation strategies during muscle fatigue, endurance and muscle performance after voluntary and electrically evoked contractions in healthy and health-compromised populations such as children with cerebral palsy (CP) and patients with facioscapulohumeral muscular dystrophy (FSHD)
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Macht, Jordon W. "THE EFFECT OF β-HYDROXY-β-METHYLBUTYRATE (HMB) SUPPLEMENTATION ON NEUROMUSCULAR PERFORMANCE FOLLOWING FATIGUING EXERCISE IN HEALTHY SUBJECTS". UKnowledge, 2015. http://uknowledge.uky.edu/khp_etds/23.
Full textAbstract:
Supporters of a nutritional supplement, β-Hydroxy-β-Methylbutyrate (HMB) supplementation, claim that it will increase the muscular strength gains and lean muscle mass gains seen during a resistance training program. It has been suggested that HMB supplementation does this by preventing muscle damage or by regenerating damaged muscle cell membranes. However, no research has evaluated the effect of HMB supplementation on low frequency fatigue. Therefore, the purpose of this study was to determine if three weeks of HMB supplementation could attenuate the effects of low frequency fatigue caused by eccentric muscle contractions of the tibialis anterior muscle. A total of 33 healthy recreationally active subjects (18 males, 15 females; 23.2 ± 4.3 yr) were recruited for this study. All subjects preformed 4 sets of 25 eccentric contractions of the tibialis anterior muscle through a range of motion of 30 degrees. Recovery measures were taken for 20 minutes after the fatigue protocol and at 48 and 96 hours of recovery. The recovery measures included: Maximum voluntary contraction peak torque, 10 Hz peak torque, 50 Hz peak torque, 10/50 Hz peak torque ratio, and EMG measurements. Each subject served as their own control and limbs were randomly assigned to pre-supplement or post-supplement limbs. Following the pre-supplement fatigue protocol and recovery measures each subject completed three weeks of 3g/day HMB supplementation. After the supplementation period the post-supplement fatigue protocol was completed and recovery measures were taken. The 10 Hz peak torque and the 10/50 Hz torque ratio in the pre-supplement limb was still significantly reduced at the 96-hour recovery measurement time, indicating that it was still showing low frequency muscle fatigue at this time. Furthermore, the post-supplement limb, recovered from the fatigue protocol faster, and did not show any signs of low frequency muscle fatigue at the 48-hour recovery measurement time. In addition the pre-supplement limb had significant maximum voluntary contraction torque deficit at the 48-hour recovery measurement time and the post-supplement limb showed no significant deficits. The main findings of this study were that three weeks of HMB supplementation attenuated low frequency fatigue and maximum voluntary contraction torque reduction after an eccentric fatigue protocol.
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Kilfoil, Monica Rosemonde. "Reliable isokinetic evaluation of strength and neuromuscular fatigue to determine the effects of pyridostigmine in subjects with post-poliomyelitis syndrome." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56980.
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Two subject groups, seven PPS (4 males, 3 females) and 15 normal controls (9 females, 6 males) were matched on the basis of age, height and weight and participated in this study. Three repeated measurements were conducted to evaluate the reliability of isokinetic measurement of strength (at 4 velocities) and fatigability (25 reciprocal contractions at 3.14 rads.s$ sp{-1}$). Data from two subsequent test days were used to evaluate the fatigue responses of the PPS subjects while ON or OFF pyridostigmine. Significant strength differences were seen between the two groups, however there was no observed difference in the rate of development of fatigue. Reliability of strength was demonstrated for the knee extensors and flexors of the PPS subjects after three consecutive test days. Fatigability of the knee extensors in PPS subjects could be tested reliably after three test days but more time would be required for reliable performance of the knee flexors. Reliability of strength and fatigability was seen for both the knee extensor and flexors of the normal controls after only two consecutive test days. A beneficial effect of the drug on fatigability was not seen in the three female PPS subjects, but was demonstrated in one male subject. The drug appeared to have a beneficial effect on strength in the remaining three male subjects.