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Evans, Sarah E., i Gregory Steeger. "Deployment-to-dwell metrics and supply-based force sustainment". Journal of Defense Analytics and Logistics 2, nr 1 (29.06.2018): 2–21. http://dx.doi.org/10.1108/jdal-05-2017-0009.
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Purpose In the present fast-paced and globalized age of war, special operations forces have a comparative advantage over conventional forces because of their small, highly-skilled units. Largely because of these characteristics, special operations forces spend a disproportionate amount of time deployed. The amount of time spent deployed affects service member’s quality of life and their level of preparedness for the full spectrum of military operations. In this paper, the authors ask the following question: How many force packages are required to sustain a deployed force package, while maintaining predetermined combat-readiness and quality-of-life standards? Design/methodology/approach The authors begin by developing standardized deployment-to-dwell metrics to assess the effects of deployments on service members’ quality of life and combat readiness. Next, they model deployment cycles using continuous time Markov chains and derive closed-form equations that relate the amount of time spent deployed versus at home station, rotation length, transition time and the total force size. Findings The expressions yield the total force size required to sustain a deployed capability. Originality/value Finally, the authors apply the method to the US Air Force Special Operations Command. This research has important implications for the force-structure logistics of any military force.
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Macdermid, Paul William, i Telmo Olazabal. "The Relationship between Stroke Metrics, Work Rate and Performance in Slalom Kayakers". Biomechanics 2, nr 1 (28.01.2022): 31–43. http://dx.doi.org/10.3390/biomechanics2010005.
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The purpose of this study was to assess the relationship between work rate, stroke metrics, and performance in whitewater slalom. Twelve Spanish, nationally competitive whitewater slalom kayakers took part in a simulated competition while using an instrumented kayak paddle to record stroke metrics over a simulated race, total duration and sectional splits. Performance time was highly correlated to overall power output (r2 = 0.511, p < 0.001), where kayakers demonstrated a positive pacing strategy with power output significantly decreasing over successive sectional splits (158 ± 40, 112 ± 32 and 65 ± 33 W, p < 0.001). This resulted in an increased stroke duration (p < 0.001), time to peak force (p < 0.001), a decrease in stroke peak force (p < 0.001), and rate of peak force development (p < 0.001) over elapsed time. As such, work rate is deemed an objective metric to monitor performance, prescribe training, and ascertain optimal pacing strategies in canoe slalom.
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Merrigan, Justin J., Jason D. Stone, W. Guy Hornsby i Joshua A. Hagen. "Identifying Reliable and Relatable Force–Time Metrics in Athletes—Considerations for the Isometric Mid-Thigh Pull and Countermovement Jump". Sports 9, nr 1 (31.12.2020): 4. http://dx.doi.org/10.3390/sports9010004.
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The purpose of this study was to evaluate intrasession reliability of countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) force–time characteristics, as well as relationships between CMJ and IMTP metrics. Division I sport and club athletes (n = 112) completed two maximal effort CMJ and IMTP trials, in that order, on force plates. Relative and absolute reliability were assessed using intraclass correlation coefficients (ICCs) > 0.80 and coefficients of variation (CVs) < 10%. Intrasession reliability was acceptable for the majority of the CMJ force–time metrics except for concentric rate of force development (RFD), eccentric impulse and RFD, and lower limb stiffness. The IMTP’s time to peak force, instantaneous force at 150 ms, instantaneous net force, and RFD measures were not reliable. Statistically significant weak to moderate relationships (r = 0.20–0.46) existed between allometrically scaled CMJ and IMTP metrics, with the exception of CMJ eccentric mean power not being related with IMTP performances. A majority of CMJ and IMTP metrics met acceptable reliability standards, except RFD measures which should be used with caution. Provided CMJs and IMTPs are indicative of distinct physical fitness capabilities, it is suggested to monitor athlete performance in both tests via changes in those variables that demonstrate the greatest degree of reliability.
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Philipp, Nicolas M., Dimitrije Cabarkapa, Ramsey M. Nijem i Andrew C. Fry. "Changes in countermovement jump force-time characteristic in elite male basketball players: A season-long analyses". PLOS ONE 18, nr 9 (27.09.2023): e0286581. http://dx.doi.org/10.1371/journal.pone.0286581.
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Basketball is a sport that is characterized by various physical performance parameters and motor abilities such as speed, strength, and endurance, which are all underpinned by an athlete’s efficient use of the stretch-shortening cycle (SSC). A common assessment to measure SSC efficiency is the countermovement jump (CMJ). When performed on a force plate, a plethora of different force-time metrics may be gleaned from the jump task, reflecting neuromuscular performance characteristics. The aim of this study was to investigate how different CMJ force-time characteristics change across different parts of the athletic year, within a sample of elite collegiate male basketball players. Twelve basketball players performed CMJ’s on near-weekly basis, combining for a total of 219 screenings. The span of testing was broken down into four periods: pre-season, non-conference competitive period, conference competitive period, and post-season competitive period. Results suggest that basketball players were able to experience improvements and maintenance of performance with regards to various force-time metrics, transitioning from the pre-season period into respective later phases of the in-season period. A common theme was a significant improvement between the pre-season period and the non-conference period. Various force-time metrics were subject to change, while outcome metrics such as jump height remained unchanged, suggesting that practitioners are encouraged to more closely monitor how different force-time characteristics change over extended periods of time.
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Petrovic, Milos, Dimitrije Cabarkapa, Jelena Aleksic, Damjana V. Cabarkapa, Jorgelina Ramos, Thrainn Hafsteinsson i Thordis Gisladottir. "Sex-Specific Differences in Vertical Jump Force–Time Metrics in Youth Basketball Players". Biomechanics 4, nr 4 (23.12.2024): 805–11. https://doi.org/10.3390/biomechanics4040059.
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Objective: The purpose of this study was to investigate differences in countermovement jump (CMJ) force–time metrics between male and female youth basketball players. Methods: Twenty-two female and seventeen male basketball players (ages 12–16) performed CMJs on a portable force plate system (VALD Performance). The data collected were analyzed for differences in force–time characteristics, specifically during the concentric and eccentric phases of the CMJ. Results: The results showed no statistically significant differences in anthropometric characteristics between the sexes. However, male athletes demonstrated better performance in several force–time metrics during the concentric phase of the CMJ, including concentric impulse, peak velocity, and mean power, ultimately leading to higher vertical jump heights. Sex-specific differences in the eccentric phase were less pronounced, though males exhibited greater relative eccentric mean power. Conclusions: The findings suggest that male players tend to display greater force and power-producing capabilities during the propulsive (concentric) phase of the CMJ. These differences highlight the importance of tailoring training programs to address specific needs, particularly focusing on enhancing concentric force and power production in female basketball players.
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Cabarkapa, Damjana V., Dimitrije Cabarkapa, Shay M. Whiting i Andrew C. Fry. "Fatigue-Induced Neuromuscular Performance Changes in Professional Male Volleyball Players". Sports 11, nr 6 (16.06.2023): 120. http://dx.doi.org/10.3390/sports11060120.
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The purpose of the present study was to assess pre-post practice changes in countermovement vertical jump (CVJ) force-time metrics and to determine the relationship between internal and external load variables within a cohort of professional male volleyball players. Ten elite athletes competing in one of the top professional European leagues participated in the present study. While standing on a uni-axial force plate, each athlete performed three CVJs immediately prior to the regular training session. Each athlete wore an inertial measurement unit (VertTM) through an entire practice from which the following external load metrics were obtained: Stress (i.e., an algorithm-derived metric used to quantify the percentage of high-impact movements), Jumps (i.e., the total number of jumps performed during the practice session), and Active Minutes (i.e., the total amount of time performing dynamic movements). Immediately post-practice, each athlete completed another set of three CVJs and reported their subjective measure of internal load using a Rating of Perceived Exertion (RPE) scale (Borg CR-10). While no statistically significant differences were observed in any of the force-time metrics examined in the present study pre-post practice (e.g., eccentric and concentric peak and mean force and power, vertical jump height, contraction time, countermovement depth), our findings indicate a strong positive association between RPE and Stress (r = 0.713) and RPE and Jumps (r = 0.671). However, a weak non-statistically significant correlation was observed between RPE and Active Minutes (r = −0.038), indicating that internal load seems to be more dependent on the intensity rather than the duration of the training session for this sport.
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Shen, Zhongmin. "Finsler Metrics with K = 0 and S = 0". Canadian Journal of Mathematics 55, nr 1 (1.02.2003): 112–32. http://dx.doi.org/10.4153/cjm-2003-005-6.
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AbstractIn the paper, we study the shortest time problem on a Riemannian space with an external force. We show that such problem can be converted to a shortest path problem on a Randers space. By choosing an appropriate external force on the Euclidean space, we obtain a non-trivial Randers metric of zero flag curvature. We also show that any positively complete Randers metric with zero flag curvature must be locally Minkowskian.
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Cabarkapa, Damjana V., Dimitrije Cabarkapa, Nicolas M. Philipp i Andrew C. Fry. "Competitive Season-Long Changes in Countermovement Vertical Jump Force-Time Metrics in Female Volleyball Players". Journal of Strength and Conditioning Research 38, nr 2 (luty 2024): e72-e77. http://dx.doi.org/10.1519/jsc.0000000000004713.
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Abstract Cabarkapa, DV, Cabarkapa, D, Philipp, NM, and Fry, AC. Competitive season-long changes in countermovement vertical jump force-time metrics in female volleyball players. J Strength Cond Res 38(2): e72–e77, 2024—Although force plates remain one of the most widely used tools for neuromuscular performance assessment in applied sports-specific settings, there is still a lack of scientific literature focused on studying changes in countermovement vertical jump (CVJ) performance in team sports such as volleyball, especially within the female athlete population. Thus, the purpose of the present study was to examine season-long neuromuscular performance changes in volleyball players. Eighteen National Association of Intercollegiate Athletics Division-I collegiate female athletes performed 3 maximal-effort CVJs while standing on a uniaxial force plate system sampling at 1,000 Hz at 5 different testing timepoints throughout a competitive season span (∼11 weeks). The testing sessions were separated 2–3 weeks apart and performed at the approximately same time of the day (12:00 hours). Repeated-measures analysis of variance revealed that both concentric and eccentric force-time metrics remain relatively unchanged throughout a regular season span (e.g., concentric peak force and power, eccentric impulse and duration). However, the eccentric metrics such as peak and mean power and peak velocity displayed a slight improvement after a brief tapering period purposely implemented before the post-season competition to optimize the athlete's recovery (∼15, 18, and 14% increase, respectively). In addition, the outcome metrics such as vertical jump height and reactive strength index-modified did not display notable fluctuations across the competitive season span. These findings can help coaches, sports scientists, and strength and conditioning practitioners to obtain a deeper insight into collegiate female athletes' force-time characteristics that may aid with developing adequate training regimens targeted toward optimizing on-court performance.
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Merrigan, Justin J., Jason D. Stone, Joel R. Martin, William Guy Hornsby, Scott M. Galster i Joshua A. Hagen. "Applying Force Plate Technology to Inform Human Performance Programming in Tactical Populations". Applied Sciences 11, nr 14 (16.07.2021): 6538. http://dx.doi.org/10.3390/app11146538.
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Force plate assessments, such as countermovement jumps and isometric mid-thigh pulls, examine performances (e.g., jump height, force, power) and movement strategies (e.g., asymmetries, durations), and are best suited to characterize and monitor physical capabilities, not predict injuries. To begin applying force plate technologies, users must first; (1) develop a data management plan to visualize and capture data over time; (2) select appropriate force plates for their scenario; (3) design appropriate testing protocols to ensure valid and reliable data. Force plate assessments may be added to existing testing, serve as separate testing batteries for annual profile testing to compare individuals and understand initial physical capabilities, or for more frequent testing (i.e., monthly or weekly) to monitor training-related adaptations or neuromuscular fatigue. Although these assessments inform evidence-based program designs, human performance practitioners must understand the considerations for conducting appropriate force plate testing, as well as proper visualizations and management of force plate data. Thus, the aim of this review is to provide evidence-based practices for utilizing force plates in tactical populations (e.g., military, firefighters, police). This includes best practices to implement testing for performance profiling, training adaptations, and monitoring neuromuscular fatigue and force asymmetries. Of note, due to the large amount of force-time metrics to choose from, this article provides general examples of important metrics to monitor and training recommendations based on changes to these force-time metrics, followed by specific examples in three case studies.
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Philipp, Nicolas, Dimitrije Cabarkapa, Drake Eserhaut, Damjana Cabarkapa i Andrew Fry. "COUNTERMOVEMENT JUMP FORCE-TIME METRICS AND MAXIMAL HORIZONTAL DECELERATION PERFORMANCE IN PROFESSIONAL MALE BASKETBALL PLAYERS". Journal of Applied Sports Sciences 2, nr 2022 (20.12.2022): 11–27. http://dx.doi.org/10.37393/jass.2022.02.2.
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Basketball is a sport that relies heavily on an athlete’s ability to rapidly decelerate in order to change direction, avoid a defender, or create space. Recent literature has proposed novel ways of measuring maximal horizontal deceleration using radar technology. The aim of this study was to investigate the relationships between different countermovement jump (CMJ) force-time characteristics and metrics related to maximal horizontal deceleration for a sample of professional male basketball players. To gain further insight into performance qualities that influence horizontal deceleration performance, athletes were separated into high- and low-performance groups for all horizontal deceleration metrics, using a median split analysis, and differences in CMJ force-time metrics were investigated between groups. The results revealed no significant correlations between any CMJ force-time metrics and horizontal deceleration performance. However, athletes’ height and body mass were correlated with different deceleration performance measures, such as average deceleration, horizontal deceleration impulse, and time to stop. Higher performing athletes with regards to average horizontal deceleration and horizontal braking impulse relative to body mass generated greater concentric power (effect size (ES) = 1.04, ES = 0.86) and concentric velocities (ES = 1.17, ES = 0.97), as well as greater jump heights (ES = 1.19, ES = 0.99). Reactive Strength Index modified values were also greater in the higher performing group for horizontal braking impulse relative to body mass (ES = 1.06). On the other hand, higher-performing athletes with regard to horizontal braking impulse generated greater eccentric deceleration force (ES = 0.81) and eccentric power values (ES = 0.88) in the CMJ. Findings may be of interest to practitioners physically preparing basketball players for the sport-specific deceleration actions they may encounter.
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Cabarkapa, Dimitrije, Damjana V. Cabarkapa, Nicolas M. Philipp, Olivera M. Knezevic, Dragan M. Mirkov i Andrew C. Fry. "Pre-Post Practice Changes in Countermovement Vertical Jump Force-Time Metrics in Professional Male Basketball Players". Journal of Strength and Conditioning Research 37, nr 11 (listopad 2023): e609-e612. http://dx.doi.org/10.1519/jsc.0000000000004608.
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Abstract Cabarkapa, D, Cabarkapa, DV, Philipp, NM, Knezevic, OM, Mirkov, DM, and Fry, AC. Pre-post practice changes in countermovement vertical jump force-time metrics in professional male basketball players. J Strength Cond Res 37(11): e609–e612, 2023—Despite the countermovement vertical jump (CVJ) being one of the most popular noninvasive and time-efficient methods for monitoring neuromuscular status, there is a lack of scientific literature focused on examining fatigue-induced alterations in performance in elite athletes. Thus, the purpose of this study was to examine changes in force-time metrics pre-post practice in professional male basketball players. Seventeen athletes competing in first-tier and second-tier national basketball leagues in Europe participated in this study. While standing on a uniaxial force plate sampling at 1,000 Hz, each athlete completed 3 CVJs pre-practice and post-practice. The practice consisted of individual and team shooting drills, position-specific player development drills, 5-on-0 offensive actions, and 5-on-5 play, including full-court transition (∼2 hours). The findings reveal that pre-post practice changes in force-time metrics seem to be phase specific. Despite a trivial increase in eccentric mean force (920.4 ± 100.2, 929.4 ± 100.0 N), most changes were observed within the concentric phase of the CVJ. The concentric phase duration increased pre-post practice (0.233 ± 0.027, 0.242 ± 0.033 seconds), whereas concentric impulse (262.9 ± 18.8, 258.6 ± 21.6 N·s), peak velocity (2.93 ± 0.22, 2.86 ± 0.22 m·s−1), mean force (2052.4 ± 179.2, 2002.7 ± 188.2 N), mean power (3,165.5 ± 269.5, 3,030.9 ± 326.8 W), and peak power (5,523.4 ± 607.3, 5,246.6 ± 663.7 W) experienced a significant decrease. Moreover, alongside longer contraction time (0.663 ± 0.065, 0.686 ± 0.074 seconds), lower vertical jump height (41.0 ± 6.8, 38.9 ± 6.6 cm) and reactive strength index-modified (0.634 ± 0.113, 0.579 ± 0.111 m·s−1) values were observed post-practice. Overall, these findings may allow practitioners to detect fatigue-induced changes in CVJ force-time metrics in professional male basketball players that can ultimately improve the acute and longitudinal training-adaptation monitoring process.
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Rendos, Nicole K., Jeffrey D. Simpson, Hoon Kim i John R. Harry. "Phase-Specific Force And Time Metrics During Vertical Hopping In Chronic Ankle Instability". Medicine & Science in Sports & Exercise 54, nr 9S (wrzesień 2022): 210–11. http://dx.doi.org/10.1249/01.mss.0000877660.90348.86.
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Moskovitz, Elad, i Adir Even. "The Impact of a BI-Supported Performance Measurement System on a Public Police Force". International Journal of Business Intelligence Research 5, nr 1 (styczeń 2014): 13–30. http://dx.doi.org/10.4018/ijbir.2014010102.
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Performance measurement, as an effective tool for implementing organizational strategy and assisting ongoing control and surveillance, is broadly adopted today. The performance measurement system (PMS) explored in this case study was implemented, using business intelligence (BI) technologies, for a public police force. The system lets police commanders view and analyze the performance scores of their own units and get feedback on the success of their activities. The study examines the system's impact, through analysis of the metric results over a time period of five years. The results show that the vast majority of the metrics examined indeed improved. Further, the results underscore the moderation effect of relative metrics weights, as well as the different behavior of metrics that reflect activity versus those that reflect outcomes. The study underscores both the positive and the negative aspects of those results, and discusses their implications for future PMS implementation with BI technologies.
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Wei, Terence, i Hans Dorfi. "Identification of Tire Force and Moment (F&M) Characteristics That Improve Combined Slip Handling Performance". Tire Science and Technology 47, nr 1 (1.03.2019): 55–76. http://dx.doi.org/10.2346/tire.19.160109.
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ABSTRACT Since tires generate the control forces required for the operation of a vehicle, the tire force and moment (F&M) characteristics have to be designed such that the vehicle can easily be kept under driver control under many driving conditions. However, the relationship between F&M characteristics and vehicle handling performance is not well understood for many driving maneuvers. A better understanding of this relationship would thus provide insight into how to improve the matching between tires and vehicles for increased vehicle stability. Building a large number of tires with different characteristics would be too expensive and time consuming, so an investigation using simulations is preferred. However, one problem with simulations is that handling performance cannot be evaluated by a professional driver (subjective metrics), unlike in outdoor tests. A way of evaluating handling performance in simulation through objective metrics is therefore necessary. In this study, the focus is on vehicle handling performance during simultaneous cornering and braking. Desirable F&M metrics were identified using the following process: Handling simulations were validated using instrumented vehicle measurements of handling behavior at outdoor test facilities. An objective handling metric (peak body slip angle) was identified that has high correlation with professional driver ratings (subjective metric) of combined slip handling performance. The objective metric could therefore be used with simulations to predict the professional driver rating. Many virtual tires were generated by changing F&M characteristics of Pacejka tire models. These virtual tires were used in simulations of combined slip handling maneuvers and evaluated for performance using the objective handling metric. By identifying which changes to F&M metrics had high correlation to changes in handling performance, the primary influencing characteristics were determined. These results were also confirmed by looking at the correlation between F&M metrics of actual tires and their subjective ratings.
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Cabarkapa, Dimitrije, Quincy R. Johnson, Damjana V. Cabarkapa, Nicolas M. Philipp, Drake A. Eserhaut i Andrew C. Fry. "Changes in Countermovement Vertical Jump Force-Time Metrics During a Game in Professional Male Basketball Players". Journal of Strength & Conditioning Research 38, nr 7 (lipiec 2024): 1326–29. http://dx.doi.org/10.1519/jsc.0000000000004795.
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Abstract Cabarkapa, D, Johnson, QR, Cabarkapa, DV, Philipp, NM, Eserhaut, DA, and Fry, AC. Changes in countermovement vertical jump force-time metrics during a game in professional male basketball players. J Strength Cond Res 38(7): 1326–1329, 2024—As technology within elite basketball advances and is more available to sporting organizations, novel approaches for assessing and addressing athletic performance during practice or competition are being continuously explored. The aim of this investigation was to examine changes in neuromuscular performance during live basketball play. Eight professional male basketball players volunteered to participate in this study. The testing procedures were conducted during a pre-tournament camp over a span of 2 days. During the first day, the athletes were familiarized with the testing procedures, and baseline measurements were obtained. Using a uni-axial force plate system sampling at 1,000 Hz, each athlete performed 3 countermovement vertical jumps (CVJ) without an arm swing before proceeding with their regular training activities. During the second day of the pre-tournament camp, the athletes repeated identical CVJ testing procedures before the start of the first quarter and post-first, second, third, and fourth quarter of a simulated 5-on-5 basketball game. Repeated-measures testing design was used to examine statistically significant differences in various force-time metrics of interest in comparison to the baseline levels (p < 0.05). Besides a trivial decrease in eccentric mean force, the findings of this study revealed no statistically significant changes in any force-time metrics of interest within both eccentric and concentric phases of the CVJ (i.e., mean and peak force and power, jump height, impulse, velocity, and contraction time). Thus, we can conclude that these variables were not sensitive to acute fatigue, suggesting that the neuromuscular performances of professional male basketball players tend to remain unchanged throughout a 5-on-5 simulated game.
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Ebersole, Marissa L., i Thomas J. Armstrong. "Inter-Rater Reliability for Hand Activity Level (HAL) and Force Metrics". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 46, nr 13 (wrzesień 2002): 1037–40. http://dx.doi.org/10.1177/154193120204601307.
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Observational rating methods are used frequently in ergonomic job analysis because they are less costly and time consuming than other methods. The ACGIH recently published a threshold limit value (TLV) for repetitive work. This TLV suggests the use of one such observational method developed by Latko et al. (1997) for rating Hand Activity Level (HAL) and peak force. One criticism of Latko's method is the unknown reliability and consistency of the raters during the analysis process. Latko suggests the use of two or more trained observers to increase this consistency. This study analyzed 410 jobs at an automotive assembly plant using 2 observers recording initial and final ratings. A weighted kappa was calculated for the HAL and peak force before and after discussion. Before discussion, HAL reliability was rated as moderate and peak force as fair. After discussion, both HAL and peak force kappa values were rated as good.
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Merrigan, Justin J., Jason D. Stone, William J. Kraemer, Emaly A. Vatne, James Onate i Josh A. Hagen. "Female National Collegiate Athletic Association Division-I Athlete Injury Prediction by Vertical Countermovement Jump Force-Time Metrics". Journal of Strength & Conditioning Research 38, nr 4 (kwiecień 2024): 783–86. http://dx.doi.org/10.1519/jsc.0000000000004758.
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Abstract Merrigan, JJ, Stone, JD, Kraemer, WJ, Vatne, EA, Onate, J, and Hagen, JA. Female National Collegiate Athletic Association Division-I athlete injury prediction by vertical countermovement jump force-time metrics. J Strength Cond Res 38(4): 783–786, 2024—Vertical countermovement jump (CMJ) assessments on force plates have been purported to screen for musculoskeletal injury risk (MSKI) but with little scientific support. Thus, this study aimed to identify associations and noncontact lower-body injury predictability with CMJ force-time metrics in female athletes. The study entailed a retrospective analysis of routine injury and performance monitoring from 155 female National Collegiate Athletics Association Division I athletes. Noncontact lower-body injuries included in analysis were confirmed by medical staff, occurred during competition or training, resulted in time loss from training, and occurred within 3 months following CMJ testing (2 maximal effort, no arm swing, jumps on dual force plates). A total of 44 injuries occurred within 3 months following CMJ baseline testing and resulted in an average of 24.5 missed days from training. Those who sustained an injury were more likely to sustain another injury (15 of 44 injuries [33.1%]; odds ratio = 3.05 [95% CI = 1.31–6.99]). For every 1-unit increase from the mean in eccentric mean power and minimum eccentric force, there was a decrease in odds of sustaining a MSKI. Despite high overall model accuracy (85.6%), the receiving operating characteristic area under the curve (65.9%) was unacceptable and the true positive rate (recall) was 0.0%. Thus, no injuries in the testing data set were correctly classified by the logistic regression model with CMJ force-time metrics as predictors. Baseline CMJ assessment may not be useful for noncontact lower-body musculoskeletal injury screening or predictability in National Collegiate Athletics Association female athletes.
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Kahya, E., F. F. Ozduven i Y. Aslan. "YOLOv5 Model Application in Real-Time Robotic Eggplant Harvesting". Journal of Agricultural Science 16, nr 2 (15.01.2024): 9. http://dx.doi.org/10.5539/jas.v16n2p9.
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Deep learning studies in agricultural automation have accelerated in recent years due to its benefits such as increasing product efficiency and reducing labor force. Deep learning is a powerful tool for automation in agriculture with applications ranging from disease identification and crop yield detection to fruit ripeness classification. It helps to automate various processes in agriculture and to perform time-consuming tasks in a shorter time. It quickly processes the data required for robotic harvesting systems and makes it available to the system. In this study, a machine learning study was carried out to be used in the robotic harvesting of eggplant fruit, which is a product that can take time to select and collect in the agricultural area where it is cultivated. YOLOv5 (nano-small-medium and large models) was used for the deep learning method. All training and test metric values of the models were analyzed. It was determined that the most successful model was the model trained with YOLOv5m algorithm on images of 640 × 640 size with 12 Batches and 110 Epochs. The results of the model values were analyzed as “metrics/precision”, “metrics/recall”, “metrics/mAP_0.5” and “metrics/mAP_0.5:0.95”. These are key metrics that measure the detection success of a model and indicate the performance of the relevant model on the verification dataset. It was determined that the metric data of the “YOLOv5 medium” model was higher compared to other models. The YOLOv5m model gave the highest score with F1 score of 85.66%, precision of 95.65%, recall of 96.15%, and mAP at 0.5:0.65 of 78.80%. Hence, it was understood that “Model 3” was the best detection model to be used in robotic eggplant harvesting to separate the eggplant from branch.
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Marques, Mário, Helena Gil, Rui Ramos, Aldo Costa i Daniel Marinho. "Relationships Between Vertical Jump Strength Metrics and 5 Meters Sprint Time". Journal of Human Kinetics 29, nr 1 (1.09.2011): 115–22. http://dx.doi.org/10.2478/v10078-011-0045-6.
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Relationships Between Vertical Jump Strength Metrics and 5 Meters Sprint TimeThe aim of this study was to examine the relationship between short sprint time (5 m) and strength metrics of the countermovement jump (CMJ) using a linear transducer in a group of trained athletes. Twenty-five male, trained subjects volunteered to participate in the study. Each volunteer performed 3 maximal CMJ trials on a Smith machine. Peak instantaneous power was calculated by the product of velocity taken with the linear transducer. For sprint testing, each subject performed three maximum 5 m sprints. Only the best attempt was considered in both tests. Pearson product-moment correlation coefficients between 5 m sprint performance and strength metrics of the CMJ were generally positive and of clear moderate to strong magnitude (r = -0.664 to -0.801). More noticeable was the significant predictive value of bar displacement time (r= ~0.70) to sprint performance. Nevertheless, a non-significant predictive value of peak bar velocity and rate of force development measurements was found. These results underline the important relationship between 5 m sprint and maximal lower body strength, as assessed by the force, power and bar velocity displacement. It is suggested that sprinting time performance would benefit from training regimens aimed to improve these performance qualities.
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Fletcher, Elliot. "An investigation on sex-based disparities in male and female collegiate athlete reactive strength index". Graduate Journal of Sports Science, Coaching, Management, & Rehabilitation 1, nr 3 (7.06.2024): 40. http://dx.doi.org/10.19164/gjsscmr.v1i3.1523.
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Reactive strength is the ability to effectively use a fast stretch shortening cycle (SSC) with the eccentric into a concentric contraction (Rebelo et al., 2022, Healthcare, 10, 593). A fast SSC is determined to be <200 ms due to a preliminary study by (Schmidtbleicher & Komi, 1992, Encyclopedia Sports Med. Vol. 3 Strength and Power in Sport) reviewing muscular contractions. Reactive strength is determined through two different metrics used within the literature which are ground contact time (GCT) and jump height (JH) allowing for understanding on how an athlete can utilise the myotatic reflex to react with the floor. Reactive Strength Index (RSI) is typically measured via drop jump (DJ) and 10/5 reactive pogo jumps. A novel way to measure RSI is via a rebound countermovement jump (RCMJ) which utilises RSI-Modified and includes time to take off instead of ground contact time. RSI is an important metric to measure because it has implications within sport-specific metrics like sprinting and jumping (Jarvis et al., 2022, Sports Med, 52, 301-330). However, some of the limitations of RSI are it is a ratio metric, and therefore RSI can mask underpinning metrics. As a result, additional metrics such as such a force, velocity and power can help better understand athlete development and the underpinning key performance indicators. However, many metrics within reactive jumps remain unsearched. Data will be collected from around 16 university athletes aged 18-25 currently competing in sport with at least one year’s experience in resistance training. Data will be collected using Hawkins dynamic force plates, sampling at 1000 Hz, and has recently been reported to be valid and reliable (Badby et al., 2023, Sports, 23, 4820) Participants will be asked to complete 3 DJ, RCMJ and 10/5 jump trials on two separate occasions separated by a minimum of 48 hours. Athletes will be instructed to perform a quiet standing period for 1 second before and after each jump to calculate body weight by the 5 × standard deviation method. Therefore, the study aims to compare the disparities between all three jumps aswell, sexes and the potential implications on performance. Previous studies displayed significant disparities between male and female participants. Therefore, the null hypothesis for this study is to display a non-significant difference across sexes aswell as between jumps. A limitation to this study is controlling the standardisation of variables such as squat depth during all tests.
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Kurhan, M. B., N. A. Muhina i O. S. Chernyshova. "THE FORECASTING EFFORT CHANGES IN TRACTION ENERGY OF METRICS AT ANY SPEED LIMITS". Science and Transport Progress, nr 27 (25.05.2009): 121–24. http://dx.doi.org/10.15802/stp2009/14246.
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Cabarkapa, Dimitrije, Damjana V. Cabarkapa, Andrew C. Fry, Yu Song, Thordis Gisladottir i Milos Petrovic. "Comparison of Vertical Jump Force–Time Metrics Between ACL-Injured and Healthy Semi-Professional Male and Female Soccer Players". Sports 12, nr 12 (6.12.2024): 339. https://doi.org/10.3390/sports12120339.
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Given the increasing use of innovative force plate systems in applied sports settings and the impact that anterior cruciate ligament (ACL) injuries have on team success, the purpose of the present study was to compare the lower-body neuromuscular performance characteristics of athletes who underwent ACL reconstruction (ACLR) and their non-injured counterparts (i.e., healthy controls). Forty-five male (thirteen injured) and twenty-six female (ten injured) semi-professional soccer players volunteered to participate in the present study. Each athlete performed three countermovement vertical jumps (CMJs) while standing on a uniaxial force plate system sampling at 1000 Hz. The injured athletes completed a nine-month recovery protocol and were screened 11–13 months post-ACLR. The dependent variables included the force–time metrics within both the eccentric and concentric phases of the CMJ. Independent t-tests or Mann–Whitney U-test were used to examine statistically significant (p < 0.05) differences in each variable (i.e., ACL-injured vs. healthy controls). The results revealed no significant between-group differences in any CMJ force–time metrics of interest (e.g., concentric peak force, eccentric mean power, countermovement depth) between ACL-injured and non-injured athletes, including inter-limb asymmetry measures (i.e., peak takeoff and landing force). Besides implying the effectiveness of the implemented rehabilitation protocol, these findings suggest that the CMJ may not present a sufficient neuromuscular performance stimulus needed to expose lower-limb asymmetries and strength and power deficiencies 11–13 months post-ACLR.
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DeVogel, Nicholas, N. Yoganandan, A. Banerjee i F. A. Pintar. "Hierarchical process using Brier Score Metrics for lower leg injury risk curves in vertical impact". BMJ Military Health 166, nr 5 (31.01.2019): 318–23. http://dx.doi.org/10.1136/jramc-2018-001124.
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IntroductionParametric survival models are used to develop injury risk curves (IRCs) from impact tests using postmortem human surrogates (PMHS). Through the consideration of different output variables, input parameters and censoring, different IRCs could be created. The purpose of this study was to demonstrate the feasibility of the Brier Score Metric (BSM) to determine the optimal IRCs and derive them from lower leg impact tests.MethodsTwo series of tests of axial impacts to PMHS foot–ankle complex were used in the study. The first series used the metrics of force, time and rate, and covariates of age, posture, stature, device and presence of a boot. Also demonstrated were different censoring schemes: right and exact/uncensored (RC-UC) or right and uncensored/left (RC-UC-LC). The second series involved only one metric, force, and covariates age, sex and weight. It contained interval censored (IC) data demonstrating different censoring schemes: RC-IC-UC, RC-IC-LC and RC-IC-UC-LC.ResultsFor each test set combination, optimal IRCs were chosen based on metric–covariate combination that had the lowest BSM value. These optimal IRCs are shown along with 95% CIs and other measures of interval quality. Forces were greater for UC than LC data sets, at the same risk levels (10% used in North Atlantic Treaty Organisation (NATO)). All data and IRCs are presented.ConclusionsThis study demonstrates a novel approach to examining which metrics and covariates create the best parametric survival analysis-based IRCs to describe human tolerance, the first step in describing lower leg injury criteria under axial loading to the plantar surface of the foot.
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Merrigan, Justin J., Jason D. Stone, Jad Ramadan, Joshua A. Hagen i Andrew G. Thompson. "Dimensionality Reduction Differentiates Sensitive Force-Time Characteristics from Loaded and Unloaded Conditions throughout Competitive Military Training". Sustainability 13, nr 11 (28.05.2021): 6105. http://dx.doi.org/10.3390/su13116105.
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The purpose was to evaluate neuromuscular fatigue’s effect on unloaded and loaded countermovement jump (CMJ) force-time characteristics during high-intensity tactical training. Eighteen male and sixteen female Marines completed two maximal effort CMJs, in unloaded (PVC pipe) and loaded (10 kg weight vest and 20 kg barbell) conditions, prior to, and 24, 48, and 72 h after starting the 4-day event. The top three variables from three principal components (PC) were analyzed using mixed-effects modeling (PC1—concentric mean power, eccentric peak force, and modified reactive strength index; PC2—countermovement depth, eccentric mean power, and eccentric mean velocity; PC3—braking duration, jump height, peak power). Metrics from PC1 and PC3 were reduced across training and from both loading conditions. Metrics from PC2 were similarly affected by external loading but were less influenced by training-induced fatigue. Jump performances with the barbell and with shallower countermovement depths did not change throughout training. Thus, 20 kg loaded CMJs are stable neuromuscular measures suitable for tracking chronic training adaptations. Monitoring unloaded and 10 kg loaded CMJ performances, along with movement strategies (i.e., countermovement rates and depth), may help identify moments of accumulated fatigue to inform training and recovery adjustments and improve the sustainability of personnel.
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Wang, Jinfeng, Muye Pang, Peixuan Yu, Biwei Tang, Kui Xiang i Zhaojie Ju. "Effect of Muscle Fatigue on Surface Electromyography-Based Hand Grasp Force Estimation". Applied Bionics and Biomechanics 2021 (15.02.2021): 1–12. http://dx.doi.org/10.1155/2021/8817480.
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Surface electromyography- (sEMG-) based hand grasp force estimation plays an important role with a promising accuracy in a laboratory environment, yet hardly clinically applicable because of physiological changes and other factors. One of the critical factors is the muscle fatigue concomitant with daily activities which degrades the accuracy and reliability of force estimation from sEMG signals. Conventional qualitative measurements of muscle fatigue contribute to an improved force estimation model with limited progress. This paper proposes an easy-to-implement method to evaluate the muscle fatigue quantitatively and demonstrates that the proposed metrics can have a substantial impact on improving the performance of hand grasp force estimation. Specifically, the reduction in the maximal capacity to generate force is used as the metric of muscle fatigue in combination with a back-propagation neural network (BPNN) is adopted to build a sEMG-hand grasp force estimation model. Experiments are conducted in the three cases: (1) pooling training data from all muscle fatigue states with time-domain feature only, (2) employing frequency domain feature for expression of muscle fatigue information based on case 1, and 3) incorporating the quantitative metric of muscle fatigue value as an additional input for estimation model based on case 1. The results show that the degree of muscle fatigue and task intensity can be easily distinguished, and the additional input of muscle fatigue in BPNN greatly improves the performance of hand grasp force estimation, which is reflected by the 6.3797% increase in R2 (coefficient of determination) value.
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Reiter, Charles R., Carolyn Killelea, Mallory S. Faherty, Ryan J. Zerega, Caroline Westwood i Timothy C. Sell. "Force-plate derived predictors of lateral jump performance in NCAA Division-I men’s basketball players". PLOS ONE 18, nr 4 (21.04.2023): e0284883. http://dx.doi.org/10.1371/journal.pone.0284883.
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A lateral jump assessment may provide unique benefits in sports such as basketball that require multidirectional performance optimization. This study aimed to examine selected force-plate derived metrics as predictors of lateral jump task distance in men’s basketball players. Twenty-two NCAA Division-I men’s basketball players (19.4 ± 1.3 years, 95.0 ± 12.5 kg, 196.5 ± 8.1 cm) each performed six single leg lateral jumps while standing on a force plate (1200 Hz, Kistler Instrument Corp). The lateral jump task involved the subject beginning by standing on the force plate and jumping sideways off one foot and then landing on the floor with the opposite foot. Three-dimensional ground reaction force curves were used to identify the eccentric and concentric phases of the jump and variables were computed each from the lateral (y), vertical (z), and resultant (r) force traces. Peak ground reaction force (pGRF), ground reaction force angle (θr), eccentric braking rate of force development (ECC-RFD), average concentric force (CON-AVG), total jump duration, eccentric phase duration, and eccentric to total time ratio were evaluated for predictive ability. Three regression models were able to significantly (p<0.05) predict jump distance: (1) pGRFy, pGRFz, and θr (p<0.001, R2 = 0.273), (2) Relative pGRFy, Relative pGRFz, and θr ((p<0.001, R2 = 0.214), and (3) Relative CON-AVGy and Relative pGRFr (p<0.001, R2 = 0.552). While several force plate-derived metrics were identified as significant predictors, a model with Relative CON-AVGy and Relative pGRFr explained a greater variability in performance (R2 = 0.55) compared to the other variables which were low, yet also significant. These results suggest that lateral ground reaction forces can be used to evaluate lateral jump performance with the use of three-dimensional force plates. The identified predictors can be used as a starting point for performance monitoring, as basketball training interventions can be directed at specific improvements in the identified metrics.
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Ajala, Sunday, Harikrishnan Muraleedharan Muraleedharan Jalajamony i Renny Edwin Fernandez. "A CNN Regression Approach for Real-Time Estimation of Dielectrophoretic Force". ECS Meeting Abstracts MA2022-02, nr 62 (9.10.2022): 2290. http://dx.doi.org/10.1149/ma2022-02622290mtgabs.
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This research presents a supervised learning framework with a Convolutional Neural Network (CNN) to precisely quantify dielectrophoretic force () in microfluidic devices using a regression approach. As opposed to using a classification paradigm in our prior work, here we recast the estimation task as a regression problem. Micrographs of pearl-chain arrangement in a DEP sensing device were processed using a using modified CNN architectures of AlexNet, ResNet-50, MobileNetV2, and GoogLeNet in order to predict the induced on yeast cells and polystyrene microbeads. Micrographs obtained from our dielectrophoresis (DEP) experiments with varied input voltages were preprocessed and used in building these deep regression models. prediction accuracy of the models was tested for using Mean Absolute Error (MAE), Mean Absolute Relative (MRE), Mean Squared Error (MSE), R-squared, and Root Mean Square Error (RMSE) as evaluation metrics. The results from the experiments show that the performance of our regression models had better prediction accuracy and generalization ability when compared to our classification models. ResNet-50 with RMSPROP gave the best performance, with a validation RMSE of 0.0918 on yeast cells while AlexNet with ADAM optimizer gave the best performance, with a validation RMSE of 0.1745 on microbeads. This provides a baseline for further studies in the application of deep learning and dielectrophoresis for DEP force estimation. Figure 1
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Powell, M. J., C. Yuan, R. S. Dzikamunhenga, R. Tarté, E. Huff-Lonergan, S. M. Lonergan i A. M. O'Connor. "A systematic review and meta-analysis of tenderness metrics in control groups used in comparative nutrition experiments1,2". Translational Animal Science 1, nr 3 (1.09.2017): 261–76. http://dx.doi.org/10.2527/tas2017.0031.
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Abstract This review reports the pork quality attributes, Warner-Bratzler Shear Force, Slice Shear Force, Star Probe, pH, marbling, color (Minolta L*/L or Hunter L*/L), and sensory tenderness evaluation, in control groups used in comparative nutrition experiments over the past 20 yr. The original aim of this study was to evaluate if changes in pork quality based on the above metrics occurred over time. To address this question, it was anticipated that data may come from 3 sources with decreasing relevance: representative retail pork surveys, representative post-harvest carcass surveys, and control groups from comparative nutrition experiments. To identify the study population, a review of studies reported in Centre for Agricultural Biosciences International Abstracts (Web of Knowledge; 1994–2014) was conducted. Two national level surveys of retail pork and 146 relevant nutritional experiments studies, with 228 control groups, were identified by the search. It was not possible to conduct a meta-analysis of the retail pork surveys based on only 2 time points. For the comparative studies, a random effects meta-analysis was conducted with year as a covariate to assess the impact of time on the outcome. In the absence of modifiers, there was no evidence of meaningful change in the mean Warner-Bratzler Shear Force, pH, color, marbling, or sensory scores over the study period. There was evidence of substantial between-study heterogeneity in the characteristics of control pigs used over the years for Warner-Bratzler Shear Force and measures of color. The absence of publicly-available representative surveys of pork quality meant the changes in pork quality over time were not clear. If changes in pork quality have occurred, the data suggest that pigs used as controls in experiments may have become less representative of commercial pigs over time and the translatability of study findings from nutrition experiments might be reduced over time. Alternately, if commercial pigs have not changed, then control pigs reflect this. The study does not address if control groups in other experimental intervention studies had similar tenderness patterns as reported here for nutritional interventions. A large amount of potentially available data was excluded from the analysis due to incomplete reporting in the original study reports.
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Merrigan, Justin J., Jason D. Stone, John P. Wagle, W. G. Hornsby, Jad Ramadan, Michael Joseph, Scott M. Galster i Joshua A. Hagen. "Using Random Forest Regression to Determine Influential Force-Time Metrics for Countermovement Jump Height: A Technical Report". Journal of Strength and Conditioning Research 36, nr 1 (28.10.2021): 277–83. http://dx.doi.org/10.1519/jsc.0000000000004154.
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Sawaya, R., R. Yilmaz, A. Bugdadi, A. Winkler-Schwartz, H. Azarnoush, G. Alsideiri i R. Del Maestro. "P.215 Tumor Heatmaps – Feedback Tool for Virtual Reality Neurosurgical Simulation". Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 48, s3 (listopad 2021): S82. http://dx.doi.org/10.1017/cjn.2021.284.
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Background: Performance Heatmaps were designed to visualize the spatial distribution of performance metrics during resection of complex tumors. This novel methodology provides experts (neurosurgeons) and trainees (residents and medical students) with visual feedback on their neurosurgical performance during operative procedures. Methods: Neurosurgeons (NS), senior residents (SR), junior residents (JR) and medical students (MS) performed resection of a complex tumor on the NeuroVR simulation platform. Metrics including time spent, force applied, and tumor volume removed were used to create Performance Heatmaps for each group. Results: During complex operative procedures, greater expertise correlated increased time spent in critical areas (NS = 121.0 s, SR = 103.0 s, JR = 86.1 s, MS = 84.9 s), increased force application (NS = 387 N, SR = 317 N, JR = 340 N, MS = 304 N), and increased tumor removal (NS = .096 cc, SR = .081 cc, JR = .074 cc, MS = .069 cc). Conclusions: Performance Heatmaps further our understanding of neurosurgical expertise by identifying key differences between experts (neurosurgeons) and trainees (residents and medical students). With the adoption of competency-based curricula, intuitive feedback tools will prove essential for trainees seeking surgical mastery.
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Kanzler, Christoph M., Ramona Sylvester, Roger Gassert, Jan Kool, Olivier Lambercy i Roman Gonzenbach. "Goal-directed upper limb movement patterns and hand grip forces in multiple sclerosis". Multiple Sclerosis Journal - Experimental, Translational and Clinical 8, nr 3 (lipiec 2022): 205521732211162. http://dx.doi.org/10.1177/20552173221116272.
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Background Upper limb disability in persons with Multiple Sclerosis (pwMS) leads to increased dependence on caregivers. To better understand upper limb disability, observer-based or time-based clinical assessments have been applied. However, these only poorly capture the behavioural aspects underlying goal-directed task performance. Objective We aimed to document alterations in goal-directed upper limb movement patterns and hand grip forces in a cohort of pwMS (n = 123) with mild to moderate upper limb impairments. Methods We relied on the Virtual Peg Insertion Test (VPIT), a technology-aided assessment with a goal-directed pick-and-place task providing a set of validated digital health metrics. Results All metrics indicated significant differences to an able-bodied reference sample (p < 0.001), with smoothness, speed, and grip force control during object manipulation being most affected in pwMS. Such abnormalities negatively influenced the time to complete the goal-directed task (p < 0.001, R2 = 0.77), thereby showing their functional relevance. Lastly, abnormalities in movement patterns and grip force control were consistently found even in pwMS with clinically normal gross dexterity and grip strength. Conclusion This work provides a systematic documentation on goal-directed upper limb movement patterns and hand grip forces in pwMS, ultimately paving the way for an early detection of MS sign using digital health metrics.
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Rosdahl, Hans, David Aitken, Mark Osborne, Jonas Willén i Johnny Nilsson. "A New Versatile Jig for the Calibration and Validation of Force Metrics with Instrumented Paddles in Sprint Kayaking". Sensors 24, nr 15 (26.07.2024): 4870. http://dx.doi.org/10.3390/s24154870.
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The interest in using new technologies to obtain recordings of on-water kinetic variables for assessing the performance of elite sprint kayakers has increased over the last decades but systematic approaches are warranted to ensure the validity and reliability of these measures. This study has an innovative approach, and the aim was to develop a new versatile jig including reference force sensors for both the calibration and validation of mutual static and dynamic stroke forces as measured with instrumented paddles at the high force levels used in elite sprint kayaking. Methods: A jig was constructed using a modified gym weight stack and a frame consisting of aluminum profiles permitting a fastening of custom-made kayak paddle shaft and blade support devices with certified force transducers combined with a data acquisition system to record blade and hand forces during static (constant load) and dynamic conditions (by paddle stroke simulation). A linear motion path incorporating a ball-bearing equipped carriage with sensors for the measurement of vertical distance and horizontal displacement was attached to the frame for recordings of various position measures on the paddle. The jig design with all components is extensively described to permit replication. The procedures for assessing the accuracy of the jig force instrumentation are reported, and with one brand of instrumented paddle used as an example, methods are described for force calibration and validation during static and dynamic conditions. Results: The results illustrate that the measured force with the jig instrumentation was similar to the applied force, calculated from the applied accurate mass (within a −1.4 to 1.8% difference) and similar to the force as calculated from the applied mass with the weight stack (within a −0.57 to 1.16% difference). The jig was suitable for the calibration and validation of forces in a range relevant for elite sprint kayaking under both static and dynamic conditions. During static conditions with a force direction equal to the calibration conditions and a force range from 98 to 590 N, all values for the instrumented paddle were within a −3.4 to 3.0% difference from the jig sensor values and 28 of 36 values were within ±2%. During dynamic conditions with paddle stroke simulations at 60 and 100 strokes/min and a target peak force of 400 N, the common force variables as measured by the instrumented paddle were not significantly different from the same measures by the jig (values at 100 strokes/min: peak force; 406.9 ± 18.4 vs. 401.9 ± 17.2 N, mean force; 212.8 ± 15.4 vs. 212.0 ± 14.4 N, time to peak force; 0.17 ± 0.02 vs. 0.18 ± 0.02 s, force impulse; 90.8 ± 11.2 vs. 90.5 ± 10.8 Ns, impulse duration; 0.43 ± 0.03 vs. 0.43 ± 0.03 s). Conclusion: A novel jig with several new functions is presented that enables the calibration and validation of force measurements with instrumented paddles by providing standardized conditions for calibration and force validation during both static and dynamic conditions in a force range relevant to elite sprint kayaking.
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Amaro, Nuno, Daniel A. Marinho, Nuno Batalha, Mário C. Marques i Pedro Morouço. "Reliability of Tethered Swimming Evaluation in Age Group Swimmers". Journal of Human Kinetics 41, nr 1 (8.07.2014): 155–62. http://dx.doi.org/10.2478/hukin-2014-0043.
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AbstractThe aim of the present study was to examine the reliability of tethered swimming in the evaluation of age group swimmers. The sample was composed of 8 male national level swimmers with at least 4 years of experience in competitive swimming. Each swimmer performed two 30 second maximal intensity tethered swimming tests, on separate days. Individual force-time curves were registered to assess maximum force, mean force and the mean impulse of force. Both consistency and reliability were very strong, with Cronbach's Alpha values ranging from 0.970 to 0.995. All the applied metrics presented a very high agreement between tests, with the mean impulse of force presenting the highest. These results indicate that tethered swimming can be used to evaluate age group swimmers. Furthermore, better comprehension of the swimmers ability to effectively exert force in the water can be obtained using the impulse of force.
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Durrant, J. T., Kaylee Nyborg, Mark C. Anderson, Kent L. Gee, Grant W. Hart i Lucas K. Hall. "Challenges in measuring and quantifying sonic booms from Falcon-9 booster landings". Journal of the Acoustical Society of America 154, nr 4_supplement (1.10.2023): A148. http://dx.doi.org/10.1121/10.0023079.
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Sonic booms from Falcon-9 booster landings contribute to the overall noise of the vehicle, but obtaining high-fidelity acoustical measurements and robust metric calculations of each sonic boom pose several challenges. This paper discusses three such challenges: sonic boom metric variability from differences in vehicle trajectory and meteorology, poor low-frequency response of low-sensitivity microphones, and contamination of the sonic boom by the landing burn noise. To quantify the variability between measurements, boom metrics are compared across four separate launches from Vandenberg Space Force Base. Boom metrics calculated from microphone stations at the same location differ by as much as 10 dB from launch to launch. Next, a digital pole-shift filter helps correct the low-frequency response of low-sensitivity microphones near the pad. These filters are adjusted so the waveforms more closely match those from microphones with a superior low-frequency response. Last, to obtain a clean sonic boom waveform, tracking the noise source location and peak frequency may help to distinguish where the sonic boom ends and landing burn noise starts. However, due to similar frequency content and close spacing in time, separating the boom from the landing burn noise near the pad remains a challenge for some booms. [Work supported by USACE.]
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Weaver, Tyler B., Christine Ma i Andrew C. Laing. "Use of the Nintendo Wii Balance Board for Studying Standing Static Balance Control: Technical Considerations, Force-Plate Congruency, and the Effect of Battery Life". Journal of Applied Biomechanics 33, nr 1 (luty 2017): 48–55. http://dx.doi.org/10.1123/jab.2015-0295.
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The Nintendo Wii Balance Board (WBB) has become popular as a low-cost alternative to research-grade force plates. The purposes of this study were to characterize a series of technical specifications for the WBB, to compare balance control metrics derived from time-varying center of pressure (COP) signals collected simultaneously from a WBB and a research-grade force plate, and to investigate the effects of battery life. Drift, linearity, hysteresis, mass accuracy, uniformity of response, and COP accuracy were assessed from a WBB. In addition, 6 participants completed an eyes-closed quiet standing task on the WBB (at 3 battery life levels) mounted on a force plate while sway was simultaneously measured by both systems. Characterization results were all associated with less than 1% error. R2 values reflecting WBB sensor linearity were > .99. Known and measured COP differences were lowest at the center of the WBB and greatest at the corners. Between-device differences in quiet stance COP summary metrics were of limited clinical significance. Lastly, battery life did not affect WBB COP accuracy, but did influence 2 of 8 quiet stance WBB parameters. This study provides general support for the WBB as a low-cost alternative to research-grade force plates for quantifying COP movement during standing.
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Marques, Mário, Francisco Saavedra, Catarina Abrantes i Felipe Aidar. "Associations Between Rate of Force Development Metrics and Throwing Velocity in Elite Team Handball Players: a Short Research Report". Journal of Human Kinetics 29A, Special-Issue (1.09.2011): 53–57. http://dx.doi.org/10.2478/v10078-011-0059-0.
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Associations Between Rate of Force Development Metrics and Throwing Velocity in Elite Team Handball Players: a Short Research ReportPerformance assessment has become an invaluable component of monitoring participant's development in distinct sports, yet limited and contradictory data are available in trained subjects. The purpose of this study was to examine the relationship between ball throwing velocity during a 3-step running throw in elite team handball players and selected measures of rate of force development like force, power, velocity, and bar displacement during a concentric only bench press exercise in elite male handball players. Fitteen elite senior male team handball players volunteered to participate. Each volunteer had power and bar velocity measured during a concentric only bench press test with 25, 35, and 45 kg as well as having one-repetition maximum strength determined. Ball throwing velocity was evaluated with a standard 3-step running throw using a radar gun. The results of this study indicated significant associations between ball velocity and time at maximum rate of force development (0, 66; p<0.05) and rate of force development at peak force (0, 56; p<0.05) only with 25kg load. The current research indicated that ball velocity was only median associated with maximum rate of force development with light loads. A training regimen designed to improve ball-throwing velocity in elite male team handball players should emphasize bench press movement using light loads.
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Mezher, Marwan T., Alejandro Pereira i Tomasz Trzepieciński. "Predicting the Effect of RSW Parameters on the Shear Force and Nugget Diameter of Similar and Dissimilar Joints Using Machine Learning Algorithms and Multilayer Perceptron". Materials 17, nr 24 (20.12.2024): 6250. https://doi.org/10.3390/ma17246250.
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Resistance spot-welded joints are crucial parts in contemporary manufacturing technology due to their ubiquitous use in the automobile industry. The necessity of improving manufacturing efficiency and quality at an affordable cost requires deep knowledge of the resistance spot welding (RSW) process and the development of artificial neural network (ANN)- and machine learning (ML)-based modelling techniques, apt for providing essential tools for design, planning, and incorporation in the welding process. Tensile shear force and nugget diameter are the most crucial outputs for evaluating the quality of a resistance spot-welded specimen. This study uses ML and ANN models to predict shear force and nugget diameter responses to RSW parameters. The RSW analysis was executed on similar and dissimilar AISI 304 and grade 2 titanium alloy joints with equal and unequal thicknesses. The input parameters included welding current, pressure, welding duration, squeezing time, holding time, pulse welding, and sheet thickness. Linear regression, Decision tree, Support vector machine (SVM), Random forest (RF), Gradient-boosting, CatBoost, K-Nearest Neighbour (KNN), Ridge, Lasso, and ElasticNet machine learning algorithms, along with two different structures of Multilayer Perceptron, were utilized for studying the impact of the RSW parameters on the shear force and nugget diameter. Different validation metrics were applied to assess each model’s quality. Two equations were developed to determine the shear force and nugget diameter based on the investigation parameters. The current research also presents a prediction of the Relative Importance (RI) of RSW factors. Shear force and nugget diameter predictions were examined using SHapley (SHAP) Additive Explanations for the first time in the RSW field. Trainbr as the training function and Logsig as the transfer function delivered the best ANN model for predicting shear force in a one-output structure. Trainrp with Tansig made the most accurate predictions for nugget diameter in a one-output structure and for shear force and diameter in a two-output structure. Depending on validation metrics, the Random forest model outperformed the other ML algorithms in predicting shear force or nugget diameter in a one-output model, while the Decision tree model gave the best prediction using a two-output structure. Linear regression made the worst ML predictions for shear force, while ElasticNet made the worst nugget diameter forecasts in a one-output model. However, in two-output models, Lasso made the worst predictions.
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Donath, Lars, i Peter Wolf. "Reliability of Force Application to Instrumented Climbing Holds in Elite Climbers". Journal of Applied Biomechanics 31, nr 5 (październik 2015): 377–82. http://dx.doi.org/10.1123/jab.2015-0019.
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Multiaxial force sensors were applied to measure interaction forces during dynamic movements, such as climbing. When interaction forces are interpreted, minimal detectable changes, typical errors, and coefficients of variation of related performance metrics should be quantified. Thus, the presented study evaluated absolute and relative between-trial reliability with and without previous familiarization trials. Eleven Swiss elite climbers (5 females, 6 males) were tested during 2 repetitive climbing sequences (including 4 instrumented holds: 2 crimps, 1 undercling, 1 sloper). To ensure comparable relative intensity, females climbed at 20°, 25°, 30°, 25°, and 20° wall inclination, while males climbed at 25°, 30°, 35°, 30°, and 25°. Contact time, maximal resultant force, mean resultant force, impulse, and the number of load changes were analyzed at the lowest inclination. Acceptable to good between-trial reliability was found for nearly all holds and performance metrics. Performance analyses after 5 minutes of familiarization on the unknown boulder, which equals up to 3 trials, yielded to higher variability compared with performance analyses after several familiarization trials. Accordingly, the majority of absolute and relative reliability data improved after familiarization trails. Thus, to be detectable, interventional changes have to exceed higher biological variability during on-sight conditions than during red-point conditions.
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Robles-Palazón, Francisco Javier, Paul Comfort, Nicholas J. Ripley, Lee Herrington, Christopher Bramah i John J. McMahon. "Force plate methodologies applied to injury profiling and rehabilitation in sport: A scoping review protocol". PLOS ONE 18, nr 10 (9.10.2023): e0292487. http://dx.doi.org/10.1371/journal.pone.0292487.
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Musculoskeletal injuries are a common health problem among sporting populations. Such injuries come with a high financial burden to the involved organisations and can have a detrimental impact on the career attainment of injured individuals. Force plates are now a common tool available to sport and exercise science and medicine professionals to enable them to profile injury risk predisposition and modulate the rehabilitation process within sporting environments. This is because contemporary force plate technology is portable and affordable and often comes with software that enables the automatic and immediate feedback of test variables to key stakeholders. However, to our knowledge, to date, there has been no comprehensive review of the scientific literature pertaining to clinical applications of force plate technology. Therefore, this article presents a protocol and a methodological framework to perform a scoping review to identify and map the available scientific literature in which force plates have been applied to the injury profiling and rehabilitation of athletes. The specific aims of the scoping review are 1) to identify and describe the force plate tests, methodologies, and metrics used to screen for injury risk and guide the return of injured athletes to full-time training and competition, 2) to identify potential trends and/or differences by participants’ age, sex, and/or level of performance in tests, methodologies, and metrics selected, and 3) to identify key gaps in the existing evidence base and new questions that should be addressed in future research. The global aim of the scoping review is to improve practitioner decision-making around force plate test and variable selection when applied to the injury prevention and rehabilitation of sporting populations.
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Zadic, Alexandru, Mircea-Nicolae Ordean, Dan Monea, Vlad Teodor Grosu, Rareș-Mihai Pop, Cornelia Popovici, Emilia Florina Grosu i Sorin Simon. "Improving Balance and Technical Skills of Young Alpine Skiers: Outcomes of a 10-Week Complex Dry-Land Training Program". Applied Sciences 15, nr 5 (6.03.2025): 2831. https://doi.org/10.3390/app15052831.
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Limited research has explored the impact of balance training on young alpine skiers, despite its recognized importance in the sport. This study evaluated the effects of a 10-week dry-land balance training program on the balance and skiing technique of skiers aged 9–11 years. The program employed five training modalities: neuromuscular, plyometric, core stability, proprioceptive, and equipment-based balance training. Thirty participants were divided into experimental and control groups based on their initial SKI IQ scores. The assessments included static balance (BTS P-Walk), explosive power (BTS G-Walk), and on-snow metrics (SKI IQ; balance, pressure, and edging) using CARV technology. The statistical analysis revealed significant improvements in the experimental group for the SKI IQ (F = 13.239; p = 0.001; η2 = 0.321) in terms of the balance metric (F = 4.800; p = 0.037) and pressure metric (F = 8.084; p = 0.008), and for the static balance parameters, such as mediolateral stability in a two-legged stance (F = 4.304; p = 0.047; η2 = 0.133) and anteroposterior stability in eyes-closed conditions (F = 14.249; p = 0.001; η2 = 0.337). The single-leg stance stability and explosive force (F = 6.08; p = 0.02) also showed marked enhancements. The edging performance, however, showed no significant change. This study underscores the value of balance training for enhancing young skiers’ performance metrics and highlights wearable technology as an effective tool for real-time feedback. Integrating balance-focused programs into alpine skiing preparation can boost performance.
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Liang, Jing. "Analyzing biomechanical force characteristics in sports performance monitoring using biochemical sensors and internet of things devices". Molecular & Cellular Biomechanics 22, nr 2 (21.01.2025): 727. https://doi.org/10.62617/mcb727.
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This study explores the application of Internet of Things (IoT) devices and biochemical sensors in sports performance monitoring, focusing on the biomechanical force characteristics of athletes to address limitations in traditional methods, such as limited data types, poor real-time accuracy, and insufficient visualization. Emphasizing mechanobiological principles, the analysis targets key force-producing regions of the body—such as the feet, legs, and torso—to optimize energy efficiency, motion precision, and overall athletic performance. Biochemical sensors were employed to monitor real-time biomechanical and physiological data, while IoT devices ensured accurate data transmission, visualization, and feedback. Data accuracy was enhanced through methods such as zero correction, timestamp synchronization, and Kalman filtering, while data transmission efficiency was optimized using a lossless compression algorithm, hierarchical structuring, the MQTT protocol, and encryption via the AES algorithm. Data organization utilized a star-structured MySQL database with composite indexing for swift access. Analytical tools such as the Apriori algorithm for data correlation, linear discriminant analysis for feature extraction, and multi-source data fusion enabled detailed visualization of performance metrics. Experimental applications in football and sprinting demonstrated the effectiveness of IoT-based monitoring. Football experiments captured multi-dimensional data on technical characteristics, while sprint tests recorded precise performance metrics, including real-time speed profiling and timing accuracy. For instance, in a 100-meter sprint test, an IoT system measured an athlete's performance at 12.54 seconds with 100% accuracy, surpassing manual timing methods. These findings highlight the transformative potential of IoT devices and biochemical sensors in sports analytics, offering enhanced accuracy, real-time tracking, and actionable insights to refine athletic performance and decision-making.
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Giuliano, Francisco, Marcos A. Soriano, Victor Pino-Mulero i Jaime González-García. "Testing Consistency: Analyzing the Reliability of Two Lower Limb Isometric Force Measurements in Strength-Trained Athletes". Applied Sciences 15, nr 1 (31.12.2024): 303. https://doi.org/10.3390/app15010303.
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This study aimed to examine the intra- and inter-session reliability of kinetic variables in the isometric mid-thigh pull (IMTP) and isometric belt squat test (IBSqT) in strength-trained individuals. Fifteen men (26.9 ± 8.9 years; 1.78 ± 0.05 m; 86.9 ± 10.5 kg) and six women (23.8 ± 4.6 years; 1.66 ± 0.06 m; 65.8 ± 10.3 kg), experienced in strength training, completed a familiarization session followed by two experimental sessions. The peak force (PF) and relative peak force to body weight (RPF), were collected for both isometric tests. Additionally, force (F), impulse (I), and rate of force development (RFD) were analyzed across different time windows (50, 100, 150, 200, and 250 ms). The intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of measurement (SEM), smallest worthwhile change (SWC) and Bland-Altman plots were calculated and displayed. Intra-session reliability was excellent for PF and RPF (ICC ≥ 0.98, CV ≤ 10%) in both IMTP and IBSqT. However, RFD and IMP displayed higher variability (CV > 10%), with low to good reliability depending on time frames. Inter-session reliability was excellent for PF and RPF (ICC ≥ 0.96, CV ≤ 5.3%) in both tests. Force at various time points exhibited moderate to excellent reliability (ICC = 0.70–0.90). PF and RPF demonstrated the highest sensitivity to performance changes, with SWC0.2 values exceeding SEM. In contrast, RFD and impulse showed larger variabilities. These findings indicate that PF and RPF are the most reliable and sensitive metrics for monitoring performance. Coaches and practitioners can use IMTP and IBSqT to detect meaningful changes in maximal isometric force production.
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Kadhim, Abdulkareem A., i Sarah A. Rafea. "IMPROVED ROUTING PROTOCOLS BASED ON RPL FOR FULL IOT-WSN STACK". Iraqi Journal of Information and Communications Technology 1, nr 1 (15.12.2021): 58–69. http://dx.doi.org/10.31987/ijict.1.1.172.
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The Internet Engineering Task Force (IETF) standardized several protocols such as Constraint Application Protocol (CoAP) to run over WSN-IoT constrained devices. IPv6 is used to transmit packets over IEEE802.15.4 radio link called 6LoWPAN. The routing protocol for low power and lossy (RPL) network enable connectivity of WSN over IoT. Nodes in RPL optimized its path using objective function (OF), which depends on different node/link metrics. In this paper, the performance of IoT-WSN stack consisting of CoAP, 6LoWPAN and two proposed protocols based on RPL are evaluated. The two proposed protocols depend on a new OF based on link reliability and energy metric. The first is a modification of recently introduced protocol called Energy Threshold RPL (ETRPL) protocol. ETRPL uses the remaining energy of the preferred parent node as a metric. The other protocol used a new metric that combines energy consumption with ETX for all paths to the root called EERPL. The protocols are tested with full IoT-WSN stack and implemented using Cooja simulator. The results showed that ETRPL and EERPL performed better than standard RPL in terms of the energy consumption, average time delay, packet reception ratio, throughput and the number of dead nodes.
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Prasad, Raghu, Manivannan Muniyandi, Govindan Manoharan i Servarayan M. Chandramohan. "Face and Construct Validity of a Novel Virtual Reality–Based Bimanual Laparoscopic Force-Skills Trainer With Haptics Feedback". Surgical Innovation 25, nr 5 (29.05.2018): 499–514. http://dx.doi.org/10.1177/1553350618773666.
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Background. The purpose of this study was to examine the face and construct validity of a custom-developed bimanual laparoscopic force-skills trainer with haptics feedback. The study also examined the effect of handedness on fundamental and complex tasks. Methods. Residents (n = 25) and surgeons (n = 25) performed virtual reality–based bimanual fundamental and complex tasks. Tool-tissue reaction forces were summed, recorded, and analysed. Seven different force-based measures and a 1-time measure were used as metrics. Subsequently, participants filled out face validity and demographic questionnaires. Results. Residents and surgeons were positive on the design, workspace, and usefulness of the simulator. Construct validity results showed significant differences between residents and experts during the execution of fundamental and complex tasks. In both tasks, residents applied large forces with higher coefficient of variation and force jerks (P < .001). Experts, with their dominant hand, applied lower forces in complex tasks and higher forces in fundamental tasks (P < .001). The coefficients of force variation (CoV) of residents and experts were higher in complex tasks (P < .001). Strong correlations were observed between CoV and task time for fundamental (r = 0.70) and complex tasks (r = 0.85). Range of smoothness of force was higher for the non-dominant hand in both fundamental and complex tasks. Conclusions. The simulator was able to differentiate the force-skills of residents and surgeons, and objectively evaluate the effects of handedness on laparoscopic force-skills. Competency-based laparoscopic skills assessment curriculum should be updated to meet the requirements of bimanual force-based training.
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Roe, Gregory, Joshua Darrall-Jones, Kevin Till, Padraic Phibbs, Dale Read, Jonathon Weakley i Ben Jones. "Between-Days Reliability and Sensitivity of Common Fatigue Measures in Rugby Players". International Journal of Sports Physiology and Performance 11, nr 5 (lipiec 2016): 581–86. http://dx.doi.org/10.1123/ijspp.2015-0413.
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This study established the between-days reliability and sensitivity of a countermovement jump (CMJ), plyometric push-up, well-being questionnaire, and whole-blood creatine kinase concentration ([CK]) in elite male youth rugby union players. The study also established the between-days reliability of 1, 2, or 3 CMJs and plyometric-push-up attempts. Twenty-five players completed tests on 2 occasions separated by 5 d (of rest). Between-days typical error, coefficient of variation (CV), and smallest worthwhile change (SWC) were calculated for the well-being questionnaire, [CK], and CMJ and plyometric-push-up metrics (peak/mean power, peak/mean force, height, flight time, and flight-time to contraction-time ratio) for 1 maximal effort or taking the highest score from 2 or 3 maximal efforts. The results suggest that CMJ mean power (2 or 3 attempts), peak force, or mean force and plyometric-push-up mean force (from 2 or 3 attempts) should be used for assessing lower- and upper-body neuromuscular function, respectively, due to both their acceptable reliability (CV < 5%) and good sensitivity (CV < SWC). The well-being questionnaire and [CK] demonstrated between-days CVs >5% (7.1% and 26.1%, respectively) and poor sensitivity (CV > SWC). The findings from this study can be used when interpreting fatigue markers to make an objective decision about a player’s readiness to train or compete.
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Woodbridge, Ryan, Chloe Ryan, Josh Burkitt, Dana Ye-Lee i John Cronin. "Reliability of a Portable Fixed Dynamometer During Different Isometric Hamstring Assessments". Applied Sciences 14, nr 22 (6.11.2024): 10202. http://dx.doi.org/10.3390/app142210202.
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Hamstring strain injuries are one of the most common non-contact injuries in sport. Hamstring strength and asymmetry are two key modifiable risk factors for hamstring strain injuries; therefore, it seems important to find reliable tests for assessing hamstring strength. The purpose of this study was to determine the within- and between-session reliability of a portable fixed dynamometer for measuring hamstring strength using three different protocols. Fourteen male participants completed three hamstring isometric protocols across three testing occasions separated by seven days. Peak force, mean force and impulse all had good to excellent within- and between-session reliability for the standing hamstring, supine 90:90 and standing 90:20 assessment (CV = 2.6–11.7%, ICC = 0.74–0.99), while peak rate of force development had moderate to excellent relative consistency (ICC = 0.64–0.90) and unacceptable absolute consistency (CV = 17.1–36.6%). The 90:20 assessment produced significantly higher values (33.4–47.3%) compared to the standing and 90:90 assessments for peak force, mean force and impulse. It appears that a portable fixed dynamometer can reliably measure a range of force–time metrics during three different hamstring assessments; however, the results of the tests cannot be used interchangeably and practitioners comparing hamstring force capability between individuals/research studies need to be cognizant of this and proceed with caution.
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Davidson, Pavel, Heikki Virekunnas, Dharmendra Sharma, Robert Piché i Neil Cronin. "Continuous Analysis of Running Mechanics by Means of an Integrated INS/GPS Device". Sensors 19, nr 6 (26.03.2019): 1480. http://dx.doi.org/10.3390/s19061480.
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This paper describes a single body-mounted sensor that integrates accelerometers, gyroscopes, compasses, barometers, a GPS receiver, and a methodology to process the data for biomechanical studies. The sensor and its data processing system can accurately compute the speed, acceleration, angular velocity, and angular orientation at an output rate of 400 Hz and has the ability to collect large volumes of ecologically-valid data. The system also segments steps and computes metrics for each step. We analyzed the sensitivity of these metrics to changing the start time of the gait cycle. Along with traditional metrics, such as cadence, speed, step length, and vertical oscillation, this system estimates ground contact time and ground reaction forces using machine learning techniques. This equipment is less expensive and cumbersome than the currently used alternatives: Optical tracking systems, in-shoe pressure measurement systems, and force plates. Another advantage, compared to existing methods, is that natural movement is not impeded at the expense of measurement accuracy. The proposed technology could be applied to different sports and activities, including walking, running, motion disorder diagnosis, and geriatric studies. In this paper, we present the results of tests in which the system performed real-time estimation of some parameters of walking and running which are relevant to biomechanical research. Contact time and ground reaction forces computed by the neural network were found to be as accurate as those obtained by an in-shoe pressure measurement system.
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Soriano, Marcos A., Francisco J. Flores, Juan Lama-Arenales, Miguel Fernández-del-Olmo i Paul Comfort. "Neuromuscular Capabilities in Top-Level Weightlifters and Their Association with Weightlifting Performance". Applied Sciences 14, nr 9 (28.04.2024): 3762. http://dx.doi.org/10.3390/app14093762.
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The aim of this study was to determine the associations between the front and back squat, countermovement jump (CMJ) and deep squat jump (DSJ) force–time metrics, and weightlifting performance in top-level weightlifters. Thirteen top-level weightlifters who classified for the World Championship 2023 participated. The heaviest successful snatch and clean and jerk were recorded within a preparation session as performance indicators. The front and back squat one-repetition maximums (1RMs) were evaluated in separate training sessions. The average of three maximum CMJs and DSJs were recorded using a force plate, and jump height, propulsive net impulse, and peak power were calculated for further analysis. Pearson’s correlation coefficients were used to determine the associations between variables. Statistical significance was set at p ≤ 0.05. The front and back squat 1RMs were significant and nearly perfectly associated with weightlifting performance (p < 0.001, r = 0.98–0.99). CMJ and DSJ propulsive net impulse displayed nearly perfect associations with weightlifting performance (p < 0.001, r = 0.96–0.99), while jump height is a less promising metric to assess the weightlifters’ ballistic capabilities. This study reinforces that lower body maximum strength and ballistic capabilities are closely associated with top-level weightlifters’ performance and are of practical importance to monitor their neuromuscular function.
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Wanda, Paul A., Gang Li i Kurt A. Thoroughman. "State dependence of adaptation of force output following movement observation". Journal of Neurophysiology 110, nr 5 (1.09.2013): 1246–56. http://dx.doi.org/10.1152/jn.00353.2012.
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Humans readily learn to move through direct physical practice and by watching the movements of others. Some researchers have proposed that action observation can inform subsequent changes in control through the acquisition of a neural representation of the novel dynamics, but to date learning following observation has been described by kinematic metrics. Here we designed an experiment to consider the specificity of adaptation to novel dynamic perturbations at the level of force generation. We measured changes in temporal patterns of force output following either the performance or observation of movements perturbed by either position- or velocity-dependent dynamic environments to 1) establish whether previously described observational motor learning effects were attributable to changes in predictive limb control and 2) determine whether such adaptation reflected a learned dependence on limb states appropriate to the haptic environment. We found that subjects who observed perturbed movements produced significant compensatory changes in their lateral force output, despite never directly experiencing force perturbations firsthand while performing the motor task. The time series of observers' adapted force outputs suggested that the state dependence of observed dynamics shapes adaptation. We conclude that the brain can transform observation of kinematics into state-dependent adaptation of reach dynamics.
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Gasparini, Nicole M., Adam M. Forte i Katherine R. Barnhart. "Short Communication: Numerically simulated time to steady state is not a reliable measure of landscape response time". Earth Surface Dynamics 12, nr 6 (4.11.2024): 1227–42. http://dx.doi.org/10.5194/esurf-12-1227-2024.
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Abstract. Quantifying the timescales over which landscapes evolve is critical for understanding past and future environmental change. Computational landscape evolution models are one tool among many that have been used in this pursuit. We compare numerically modeled times to reach steady state for a landscape adjusting to an increase in rock uplift rate. We use three different numerical modeling libraries and explore the impact of time step, grid type, numerical method for solving the erosion equation, and metric for quantifying the time to steady state. We find that modeled time to steady state is impacted by all of these variables. Time to steady state varies inconsistently with time step length, both within a single model and among different models. In some cases, drainage rearrangement extends the time to reach steady state, but this is not consistent in all models or grid types. The two sets of experiments operating on Voronoi grids have the most consistent times to steady state when comparing across time step and metrics. On a raster grid, if we force the drainage network to remain stable, time to steady state varies much less with computational time step. In all cases we find that many measures of modeled time to steady state are longer than that predicted by an analytical equation for bedrock river response time. Our results show that the predicted time to steady state from a numerical model is, in many cases, more reflective of drainage rearrangement and numerical artifacts than the time for an uplift wave to propagate through a fixed drainage network.