Academic literature on the topic 'Sports Biomechanics'

An epidemiological study into the incidence of ankle sprain in elite and non-elite athletes was carried out to collect data on the incidence of sports injuries focusing specifically on ankle sprains in elite and non-elite athletes. Furthermore, to develop and validate a questionnaire to be used to collect data on the residual symptoms associated with a history of ankle sprain and functional instability. Ankle sprains accounted for 16% of all injuries and symptoms of functional instability were reported by 95% of athletes that reported sustaining an ankle sprain during the study. The questionnaire was then used to recruit subjects (19 subjects with a history of unilateral ankle sprain and functional instability and 19 healthy controls) for the subsequent experiments. Anteroposterior and medio-lateral postural sway in single-limb stance was examined using a KistierTM force platform. Each subject underwent twelve postural sway tests: three on each leg with eyes open and eyes closed. With eyes closed the injured ankle had significantly greater medial (p=O.001) and lateral (p=O.007) postural sway than the uninjured ankle. With eyes open the injured and uninjured ankles had similar postural control. With eyes open the injured ankle had significantly greater anterior (p=O.021, p=O.Oll) and posterior (p=O.019, p=O.018) postural sway than the dominant and non-dominant ankles respectively. With eyes closed the injured ankles had significantly greater medial (p=O.008, p=O.008) and lateral (p=O.014, p=O.015) postural sway than the dominant and non-dominant ankles respectively. The reaction time of peroneus longus, peroneus brevis, tibialis anterior and extensor digitorum longus to a non-pathological lateral ankle sprain mechanism was examined using a purpose built tilt platform. The platform had two moveable plates so that either ankle could be tilted spontaneously into combined plantarflexion and inversion. Electromyography was performed on each muscle and subjects had each ankle tilted six times. A computer-based onset detection method was developed to provide an objective method for identifying the onset of electromyography and tilt platform activity and calculating muscular reaction times. The injured ankle peroneus longus, peroneus brevis and tibialis anterior reaction times were significantly slower.

The foot forms the dynamic base upon which a sprinter functions. The actions that occur within the foot are of critical importance to the task of sprint running, since they influence the functional mechanisms of the entire body and especially the lower extremity. The aim of this research was to evaluate how foot function may contribute to sprinting performance and the interaction between the mechanical properties of sprinting footwear and performance, with a focus on the role of the metatarsophalangeal joint (MPJ). Currently, little is known about the effect of footwear upon the normal biomechanical function of the MPJ during sprinting, as this joint has often been neglected in previous biomechanical studies of lower limb energetics. A series of empirical and theoretical investigations were therefore undertaken to advance the understanding in this area. The initial study revealed the importance of two important methodological issues on the analysis of MPJ function during sprinting. Appropriate MPJ axes representation and appropriate data processing procedures are vital to ensure the accurate assessment of joint kinetics. Empirical investigations on eight trained sprinters performing maximal sprint trials, both in barefoot and sprint spike conditions determined normal patterns of foot behaviour and the role of the MPJ during sprinting. Several aspects of foot function, including kinematic, kinetic and pressure characteristics, were determined. Sprint spikes reduced MPJ range of motion and dorsiflexion velocity but increased total energy generated during the push-off phase, biomechanical measures which may be linked to sprinting performance. To investigate whether manipulations in the mechanical properties of sprinting footwear may influence sprinting performance and MPJ function, sprint spikes with insoles of varying stiffness's were manufactured and mechanically tested. For a group of sprinters increasing the sprint spike stiffness did not elicit an improved sprinting performance. Due to the high variability between athletes and highly individualised responses to perturbations in footwear a single- subject analyses was undertaken. This study demonstrated that individual sprinting performance may be improved by implementation of relevant shoe mechanical characteristics. Whilst varying the mechanical characteristics of sprint spikes clearly showed controlling influences over the natural motion of the MPJ, the relatively minimal effect on the resultant MPJ energetics, potentially suggests that sprint spikes do not minimise energy loss during sprinting. The combined empirical and theoretical understanding therefore highlighted several aspects of MPJ function which could be altered by footwear in an attempt to improve sprint running performance.

Whilst sports bras have been reported to significantly reduce breast kinematics and exercise-related breast pain, little is known about the effect of breast support on running biomechanics. This research area has novel applications and many potential benefits to female athletes. Papers available within this area hypothesise that the reduction of breast kinematics and exercise-related breast pain, provided by a high breast support, ensures running biomechanics are maintained and potentially enhanced, however, few have provided evidence of this. To investigate this area this thesis explored biomechanical measures during running including; breast biomechanics, full body running kinematics, and an examination of upper body muscle activity during a five kilometre treadmill run, in low and high breast support conditions. An integrated programme of work was conducted with multiple variables collected and presented in chapter four to seven. Chapter three identified significant changes in breast kinematics during a prolonged treadmill run, and defined the run duration for this programme of work. Chapter four examined breast biomechanics during a five kilometre treadmill run, in different breast support conditions. In line with previous publications, the high breast support provided superior magnitudes of support to the breasts (up to 75% reduction) compared to the lower breast support conditions, and significant reductions in exercise-related breast pain throughout treadmill running. Increases in multiplanar breast displacement, velocity, acceleration, and approximated force were reported from the start to the end of the five kilometre run in both low (increases of 7 mm, 0.10 m.s-1, 5.6 m.s-2, 3 N) and high (5 mm, 0.07 m.s-1, 2.7 m.s-2, 1 N) breast supports. These novel findings demonstrate that breast kinematics increase during a five kilometre treadmill run, which may directly affect an individual’s running biomechanics. Assessing the magnitude of variance associated with breast biomechanics data ensures accurate interpretation of the reported findings. To achieve this, within- and between participant variance in multiplanar breast kinematics were quantified utilising the coefficient of variance (Cv%). The smallest differences in breast kinematics reported in the third chapter exceeded the reported within-participant variance in both low (12 Cv%) and high (15 Cv%) breast supports, and were therefore defined as meaningful differences. Between-participant variance in multiplanar breast kinematics in low (23 Cv%) and high (29 Cv%) breast supports was greater than the within-participant variance, and should be considered in future for research designs and sample sizes. To assess running kinematics between breast supports, a full body kinematic analysis was conducted including the quantification of step length and full body Cardan joint angles. When running in the lower breast support conditions, costly running mechanics such as greater thorax flexion, shorter step length, less acute knee angle, greater arm swing mechanics, and greater axial rotation of the thorax and pelvis were reported. However, the high breast support exhibited a kinematic profile more closely aligned with a desirable, economic running style previously defined within the literature. These findings support claims that the breast support worn may impact upon biomechanical parameters, with high breast support eliciting advantageous running kinematics. This unique work found female runners will alter their running kinematics depending upon the breast support worn. Changes in running kinematics away from an individual’s natural kinematics have been linked to changes in the activation of muscles driving these movements. Therefore, given the reported differences in upper body running kinematics, the effect of breast support on the activity of six upper body muscles central to running was examined and reported. Reductions in normalised peak activity of the pectoralis major (37% reduction), anterior deltoid (26 reduction) and medial deltoid (30% reduction) were reported in the high breast support; suggesting that a high breast support significantly reduces the peak activation of these three muscles compared to lower breast support conditions during running. Furthermore, the differences in activity of these muscles are thought to be associated with the changes in upper body kinematics, specifically arm swing mechanics. The research design of this programme of work enabled relationships between the key biomechanical measures to be explored, providing a holistic view of the effect of breast support on the biomechanics of the female runner. Relationships were identified between the magnitude of breast kinematics, which is governed by the breast support worn, and the following biomechanical measures investigated; exercise-related breast pain, upper and lower body running kinematics and upper body muscle activity. Furthermore, certain running kinematics demonstrated significant relationships to muscle activity. This research has shown that breast biomechanics, running kinematics and upper body activity are affected by the breast support worn during treadmill running. The use of high breast support has demonstrated the potential of this breast support to benefit running biomechanics. This novel programme of work has progressed the knowledge of the effect of breast support on both breast and body biomechanics during treadmill running.

Approximately 45% of the points scored in international Rugby Union matches are the result of place kicks (Quarrie & Hopkins, 2015). However, the key technique characteristics underpinning this skill are not well understood. The aim of this thesis was therefore to investigate rugby place kicking technique and performance, and understand how these differ between successful and less successful place kickers. In order to objectively quantify place kick performance outcome from data collected in a laboratory environment, a novel performance measure representative of the maximum distance that any given place kick could be successful from was developed. This measure combined initial ball flight data with previously published aerodynamic forces and was shown to predict ball location with a mean error of 4.0%. Full body motion capture and ground reaction force data were then collected from 33 experienced (amateur to senior international level) kickers and three groups of kickers were identified based on their performance outcome: long, short, and wide-left kickers. Differences were observed in the initial ball flight characteristics between the three groups and specific aspects of technique were then analysed to understand how these different performance outcomes were achieved. The long and wide-left kickers used different strategies to achieve comparable forward kicking foot velocities and initial ball velocities. The wide-left kickers used a hip flexor strategy: greater positive hip flexor work which was facilitated by a stretch across the trunk at the top of the backswing, followed by longitudinal rotation throughout the downswing. In contrast, the long kickers used a knee extensor strategy: greater positive knee extensor work and a more consistent trunk orientation throughout the downswing. Although both strategies led to comparably high initial ball velocity magnitudes, the hip flexor strategy led to greater longitudinal ball spin and an initial ball velocity vector directed towards the left-hand-side. Kickers who achieve fast ball velocities but miss left could potentially benefit from technical interventions to address their trunk kinematics or development of their kicking knee extensor involvement. The long kickers achieved faster kicking foot and initial ball velocities than the short kickers. The long kickers took a more angled and faster approach to the ball compared with the short kickers. This enabled the pelvis to be less front-on at the top of the backswing, meaning that the kicking foot was further away from the ball at this point and subsequently travelled a longer path to initial ball contact. The long kickers also demonstrated greater horizontal whole-body CM deceleration between support foot contact and initial ball contact and performed greater hip flexor and knee extensor positive work than the short kickers during the downswing. Kickers who cannot generate fast ball velocities could potentially benefit from interventions to their approach direction and velocity, or from development of their kicking hip flexor and knee extensor involvement. This thesis has provided a comprehensive understanding of rugby place kicking technique and recommendations for both coaching practice and research.

The studies presented in this dissertation investigated biomechanical factors associated with sports-related brain injuries on the field and in the laboratory. In the first study, head impact exposure in youth football was observed using a helmet mounted accelerometer system to measure head kinematics. The results suggest that restriction on contact in practice at the youth level can translate into reduced head impact exposure over the course of a season. A second study investigated the effect of measurement error in the head impact kinematic data collected by the helmet mounted system have on subsequent analyses. The objective of this study was to characterize the propagation of random measurement error through data analyses by quantifying descriptive statistic uncertainties and biases for biomechanical datasets with random measurement error. For distribution analyses, uncertainties tend to decrease as sample sizes grow such that for a typical player, the uncertainties would be around 5% for peak linear acceleration and 10% for peak angular (rotational) acceleration. The third and fourth studies looked at comparisons between two headforms commonly used in athletic helmet testing, the Hybrid III and NOCSAE headforms. One study compared the headform shape, particularly looking at regions that are likely to affect helmet fit. Major differences were found at the nape of the neck and in the check/jaw regions that may contribute to difficulty with fitting a helmet to the Hybrid III headform. For the final study, the impact responses of the two headforms were compared. Both headforms were mounted on a Hybrid III neck and impacted at various magnitudes and locations that are representative of impacts observed on the football field. Some condition-specific differences in kinematic parameters were found between the two headforms though they tended to be small. Both headforms showed reasonable repeatability.<br>Ph. D.

Several methods have been used in the scientific literature to study the weightlifting pull. Broadly, these methods are used to measure kinematic or kinetic variables exhibited by the lifter, the barbell, or the lifter-barbell system. However, there is an apparent disconnect between weightlifting research and coaching practice that may reduce the perceived benefits of technique analysis among coaches and present some challenges for coaches who seek to incorporate technique analysis into their coaching practice. Differences and trends in the technique of competitive weightlifting performances are apparent from the available literature. However, there are also gaps in the literature due to infrequent analyses that are limited to narrow subgroups of the weightlifting population. Therefore, the purposes of this dissertation were to 1) update to the scientific knowledge of weightlifting technique and performance, 2) improve coaches’ ability to conduct and interpret technique analysis, and 3) enhance transferability of weightlifting in training to improve sport performance. A review of methods used to evaluate the weightlifting pull provides some practical guidance for coaches on the application and interpretation of weightlifting technique analysis. Video analysis is recommended as the most practicable method for coaches to implement technique analysis themselves. Methods used to study 319 lifts by women and men from two major international competitions demonstrate the feasibility and usefulness of video analysis as an inexpensive, time-efficient, and user-friendly method for coaches to conduct reliable technique analysis. The results of this dissertation suggest that a variety of techniques can be used to achieve international weightlifting success and provide some evidence of changes in weightlifting technique since at least the mid-1980’s. These results also indicate that a stereotypical technique profile among elite international weightlifters does not exist, which further support the notion that strength is a primary determinant of weightlifting ability.

<p>Traditionally, research on cross‐country skiing biomechanics is based mainly on experimental testing alone. Trying a different approach, this thesis explores the possibilities of using computational musculoskeletal biomechanics for cross‐country skiing. As far as the author knows, this has not been done before.</p><p>Cross‐country skiing is both fast and powerful, and the whole body is used to generate movement. Consequently, the computational method used needs to be able to handle a full‐body model with lots of muscles. This thesis presents several simulation models created in the AnyBody Modeling System, which is based on inverse dynamics and static optimization. This method allows for measurementdriven full‐body models with hundreds of muscles and rigid body segments of all major body parts.</p><p>A major result shown in the thesis is that with a good simulation model it is possible to predict muscle activation. Even though there is no claim of full validity of the simulation models, this result opens up a wide range of possibilities for computational musculoskeletal biomechanics in cross‐country skiing. Two example of new possibilities are shown in the thesis, finding antagonistic muscle pairs and muscle load distribution differences in different skiing styles. Being able to perform optimization studies and asking and answering “what if”‐questions really gives computational methods an edge compared to traditional testing.</p><p>To conclude, a combination of computational and experimental methods seems to be the next logical step to increase the understanding of the biomechanics of crosscountry skiing.</p><br><p>Traditionellt har biomekaniska forskningsstudier av längdskidåkning baserats helt och hållet på experimentella metoder. För att prova ett annat angreppssätt undersöks i denna avhandling vilka möjligheter som beräkningsbaserad biomekanik kan ge för längdskidåkning. Så vida författaren vet, har detta inte gjorts tidigare.</p><p>Längdskidåkning innehåller snabba och kraftfulla helkroppsrörelser och därför behövs en beräkningsmetod som kan hantera helkroppsmodeller med många muskler. Avhandlingen presenterar flera simuleringsmodeller skapade i AnyBody Modeling System, som baseras på inversdynamik och statisk optimering. Denna metod tillåter helkroppsmodeller med hundratals muskler och stelkroppssegment av de flesta kroppsdelarna.</p><p>Ett resultat som avhandlingen visar är att med en bra simuleringsmodell är det möjligt att förutsäga muskelaktiviteten för en viss rörelse och belastning på kroppen. Även om ingen validering av simuleringsmodellen ges, så visar ändå resultatet att beräkningsbaserad biomekanik ger många nya möjligheter till forskningsstudier av längdskidåkning. Två exempel visas, hur muskelantagonister kan hittas samt hur lastfördelningen mellan musklerna förändras då skidåkaren förändrar stilen. Att kunna genomföra optimeringsstudier samt fråga och svara på ”vad händer om”‐ frågor ger beräkningsbaserad biomekanik en fördel i jämförelse med traditionell testning.</p><p>Slutsatsen är att en kombination av beräkningsbaserade och experimentella metoder borde vara nästa steg för att addera insikt om längdskidåkningens biomekanik.</p><br>Report code: LIU‐TEK‐LIC‐2008:4. On the day of the defence date the status of article V was: Submitted.