Neuromuscular (NM) fatigue can be defined as an exercise-induced decrease in skill-based performance and/or capacity that originates within the NM system (i.e. between activation of the primary motor cortex to the performance of the contractile apparatus (Bigland-Ritchie, 1981)) (Boyas & Guével, 2011). NM fatigue is a fundamental component of athlete training and competition, required for both optimal adaptation and performance. However, in the short-term, NM fatigue can decrease performance and increase injury risk, whilst its accumulation can produce long-term deleterious performance and health consequences. Consequently, athlete fatigue monitoring is recommended for precise management of athlete training adaptation and recovery practices. Regular NM function measurement is a key component of athlete fatigue monitoring; still the best means of assessing fatigue-induced effects on NM function is presently unclear. A broader understanding of the most suitable NM testing methods, and associated NM constructs, would therefore be of value to sport practitioners. As elaborated below, this dissertation aimed to first identify the most suitable NM function test, and then develop the testing technique to better determine the NM responses associated with acute fatigue, an accumulation of exercise stress (i.e. accumulated fatigue), and post-exercise recovery. A secondary aim was to provide a greater understanding of the NM responses elicited by fatiguing exercise. First, the suitability of four NM function tests (e.g. countermovement jump (CMJ), squat jump (SJ), drop jump (DJ), 20-m sprint (SPRINT)) for the regular measurement of NM fatigue was examined. Assessment of test repeatability (mean coefficient of variation for various measures of force, velocity, power, impulse and flight time; SPRINT: 1.2%; CMJ: 3.0%; SJ: 3.5%; DJ: 4.8%) and sensitivity to NM fatigue (substantial post-exercise changes observed up to; SPRINT: 0-hr post; SJ: 24-hr post; CMJ & DJ: 72-hr post) revealed the CMJ test to be the most suitable, with it highly repeatable and sensitive to fatigue-induced changes immediately following fatiguing exercise and during post-exercise recovery. Subsequent investigations further explored the use of CMJ testing for NM fatigue detection. Second, CMJ responses to acute NM fatigue and during post-exercise recovery were examined in recreational athletes. As part of this process, two analytic approaches, anticipated to decrease measurement error and improve test sensitivity through the examination of CMJ mechanics, were utilised. Fatiguing exercise resulted in a biphasic recovery profile. Immediate decreases were evident in most CMJ variables (i.e. small-to-moderate changes), followed by mechanical changes indicative of NM fatigue (i.e. small changes in CMJ time- and rate-based variables) at 72-hour. Observation of mechanical changes at 72-hour, supported the use of the two adopted CMJ analytic approaches. Third, the developed methodology was used with elite snowboard-cross athletes to examine fatigue- and training-induced changes in NM function. Compared to concentric CMJ variables (i.e. peak/mean power/force/velocity), mechanical CMJ changes were more marked following both the fatiguing protocol (ES: moderate-to-large vs. small-to-moderate) and the 19-week training block (large-to-extremely large vs. small-to-very large). The more apparent mechanical changes observed in this highly-trained population (vs. the recreational athletes in Chapter 3) indicated that CMJ mechanical analysis may be of particular value in athlete populations. Fourth, the CMJ testing techniques were used to examine NM changes associated with accumulated fatigue (i.e. an accumulation of exercise and/or non-exercise stress) in a highly-trained population. Alongside increased training loads and decreased wellness, substantial changes in CMJ mechanics (e.g. time to peak force, force at zero velocity) and jump outcome (e.g. flight time, peak displacement) were observed, thereby supporting the inclusion of mechanical CMJ assessment for the monitoring of accumulated NM fatigue effects. This series of investigations support the use of CMJ testing for athlete NM fatigue monitoring, and highlight that NM fatigue can manifest as alterations in the mechanical strategies used to accomplish a task. These changes appear evident in response to acute fatigue (Chapters 3 and 4), alongside increases in training load (Chapters 4 and 5) and during post-exercise recovery (Chapter 3). Practitioners should therefore incorporate analyses of CMJ mechanics to provide a more comprehensive assessment of fatigue- and training-induced changes in NM function. / Graduate / gatherco@uvic.ca

In female college soccer players, there is no protocol for assessing fatigue. A total of 40 members of the Virginia Tech Women's Soccer team participated in the countermovement jump assessment to find a reliable way to gauge player fatigue and readiness in these athletes. These were tested by assessing the within and between-day similarity of a countermovement jump test as a measure of neuromuscular performance by comparing multiple jump heights during jumps performed within a single day and on separate days. Additionally, to determine the responsiveness of countermovement jump height as a marker of fatigue, we compared jump heights before and after activities thought to induce fatigue and competitive matches. All subjects wore a STATSports APEX unit that includes an 18Hz GPS, 952 Hz accelerometer, and 952 Hz gyroscope situated on the upper back over the second thoracic vertebra using a manufacturer-provided vest. After each training session or match, the data was downloaded using the manufacturer's software (APEXA). A custom MATLAB program was then used to calculate CMJ height from vertical acceleration. Results showed that CMJ heights were very reliable both within and between testing days. CMJ heights were found to accurately decrease following both high-load training sessions and a competitive soccer match. For both activities, the decrease in performance was dependent on the amount of load experienced. Lastly, CMJ height did not recover the day following high training load sessions. Across a training week, CMJ consistently decreased each day. This was followed by a recovery in performance following two off days. The results suggest that the use of a trunk-mounted, GPS-embedded accelerometer and a novel three-jump protocol is responsive to assess CMJ height. In addition, it is responsive to estimating fatigue following soccer activity. / Master of Science / In female college soccer players, there is no protocol for assessing fatigue. A total of 40 members of the Virginia Tech Women's Soccer team participated in the countermovement jump assessment to find a reliable way to gauge player fatigue and readiness in these athletes. We hypothesized that countermovement jump heights would not vary between jumps executed on the same day and on different days. We also hypothesized pre-training countermovement jump heights would vary across a 7-day training session with reductions dependent on the prior days' physical demands and would be reduced following a competitive soccer match, also dependent on each player's physical demands. These were tested by assessing the within and between-day reliability of a vertical jump test as a measure of performance by comparing multiple countermovement jump heights during jumps performed within a single day and comparing jumps on separate days. Additionally, to determine the feasibility of countermovement jump height as a marker of fatigue, we compared jump heights before and after activities thought to induce fatigue and competitive matches. All subjects wore a STATSports APEX unit that includes an 18Hz GPS, 952 Hz accelerometer, and 952 Hz gyroscope situated on the upper back over the second thoracic vertebra using a manufacturer-provided vest. After each training session or match, the data was downloaded using the manufacturer's software (APEX) and a custom MATLAB program was then used to calculate CMJ height from vertical acceleration. Results showed that CMJ heights were very reliable both within and between testing days. CMJ heights were found to decrease following both high-load training sessions and following a competitive soccer match. For both activities, the decrease in performance was dependent on the amount of load experienced. Lastly, CMJ height did not recover the day following a high training load sessions. Across a training week, CMJ consistently decreased each day. This was followed by a recovery in performance following two off days. The results suggest that the use of a trunk-mounted, GPS-embedded accelerometer and a novel three-jump protocol is reliable to assess CMJ height. In addition, it is feasible to estimating fatigue following soccer activity.

The purposes of this dissertation were to examine the phase characteristics of the countermovement jump force-time curve between athletes based on jumping ability, examine the influence of maximal muscular strength on the countermovement jump force-time curve phase characteristics of athletes, and to examine the behavior of the countermovement jump force-time curve phase characteristics over the course of a training process in athletes of varying strength levels. The following are the major findings of these dissertations. The analysis of athletes by jumping ability suggested that proficient jumpers are associated with greater relative phase magnitude and phase impulse throughout the phases contained in the positive impulse of the countermovement jump force-time curve. Additionally, phase duration was not found to differ between athletes based on jumping ability or between male and female athletes. The analysis of athletes based on maximal muscular strength suggested that only unweighted phase duration differs between strong and less-strong athletes. Interestingly, in both investigations based on jumping ability and maximal strength indicated the relative shape of the stretching phase representing the rise in positive force was related to an athlete’s jumping ability (jump height). The results of the longitudinal analysis of countermovement jump force-time phase characteristics identified that these variables can be frequently assessed throughout a training process to provide information of regarding an athlete performance state. Furthermore, based on the contrasting behaviors of many of the countermovement jump force-time curve phase characteristics over time, an athlete’s level of muscular strength may influence how these characteristics are expressed in the context of a training process.

The purpose of this study was to examine the influence of accumulated volume load on countermovement jump (CMJ) mechanical variables. Eight athletes underwent weekly CMJ testing using a force plate. Statistical changes were observed in certain CMJ variables over the observation period. Jump height (0.42±0.05 m) and allometrically scaled peak power (88.86±7.49 W·kg-0.67) exhibited multiple statistical changes. These changes appeared to exhibit a delayed effect in response to accumulated volume load. Specifically, following several weeks of large accumulated volume loads these variables declined. In addition subsequently decreasing accumulated volume loads resulted in an increase in both variables. The findings of this study indicate measuring jump height and peak power may be an effective method for monitoring a resistance training process.

The purpose of this study was to understand the relationship between back squat one-repetition maximum relative to body mass (1RMrel), countermovement jump height (CMJH), and optimal drop height in drop jump (DHopt). Fifteen male participants with various sport backgrounds and training experience completed a one repetition maximum (1RM) back squat, maximum countermovement jump (CMJ), and drop jumps (DJ) from incrementally increasing drop heights to determine which drop height elicited the greatest jump height. The DHopt testing protocol was unique in that smaller increments were used to determine DHopt compared to what has been reported in literature previously. Pearson correlation coefficients revealed that DHopt had small (r=0.214) and moderate (r=0.464) relationships with 1RMrel and CMJH, respectively. A second analysis (n=13) was conducted after two participants (i.e. powerlifters) were identified as possibly being representative of a different population. The second analysis found that DHopt had strong relationships with 1RMrel (r=0.645) and CMJH (r=0.690). Results from this study seem to suggest that individuals with greater 1RMrel and CMJH tend to have a higher DHopt. However, this relationship may not be observed among all populations due to likely differences in sport background, genetics, and/or training experience.

This study was designed to provide an overview of weightlifting performance as a function of age group and sex and evaluate the potential of countermovement jump height (CMJH) as a tool to gauge performance potential. Data from 130 youth athletes (female, n = 65 & male, n = 65) were used to examine progression of performance (Total and Sinclair total) and the relationship between CMJH and Sinclair total while considering interactions between CMJH and age and/or sex. ANOVAs with post hoc analyses revealed that both totals had a statistical first-order polynomial interaction effect between age group and sex and the difference between age groups of 12–13 and 14–15 years old was statistically greater for male than female. A linear model, developed to examine the relationship, revealed that CMJH and CMJH x sex x age rejected the null hypothesis. Our primary findings are that male youth weightlifters have a higher rate of performance progression, possibly owing to puberty, and CMJH may be a better gauging tool for older male youth weightlifters.

Bakgrund: Studier visar ett starkt samband mellan sprintprestation på bar mark och styrka i konventionella knäböj. Knäböj återfinns även i många styrkeprogram för hockeyspelare, men en potentiell nackdel med övningen är att den utsätter ländryggen för höga kompressionskrafter, något som minskar om man i stället utför en så kallad frontböj. Författaren av den här uppsatsen saknar kännedom om huruvida forskning finns gällande ett potentiellt samband mellan frontböj och sprintprestation på is. Skulle ett sådant samband finnas kan frontböj vara en alternativ övning till konventionella knäböj, detta för att minska belastningen på ländryggen utan att göra avkall på prestation. Syfte: Att avgöra om maxstyrkan i frontböj och vertikal hopphöjd korrelerar med sprintprestationen på is, hos manliga juniorhockeyspelare på elitnivå. Metod: Experimentiell studiedesign. Tretton ishockeyspelare på juniorelitnivå (ålder 17,1 ± 1,1 år; längd = 180,8 ± 7,8 cm; kroppsvikt 79,5 ± 8,8 kg) testades för maximal styrka i frontböj, vertikal hopphöjd och sprintprestation (0-10 meter) på is. Resultat: Pearson´s korrelation visade ett signifikant måttligt samband mellan maximal styrka i frontböj och sprintprestation på is (r = - 0,55, p = 0,050) samt mellan vertikalhopp (CMJ) och sprintprestation på is (r = - 0,67, p = 0,012). Det var ingen signifikant korrelation mellan 10 meter sprint och kvoten 1RM/kroppsvikt (r = - 0,48, p = 0,095). Konklusion: Den här studien pekar mot ett starkare samband mellan hopprestation och sprintprestation på is än mellan maximal styrka och sprintprestation, även om skillnaden inte är signifikant i den här studien.

The purpose of this study was to examine the effects of vertically oriented resistance training on golf driving performance. Ten Division-I collegiate golfers completed two resistance training sessions per week for 10 weeks during the fall tournament season. Pre- and post-training assessments of strength-power and golf performance were compared. To assess strength-power, jump height, peak force, and peak power were measured from static and countermovement vertical jumps; peak force and rate of force development from 0 to 250 ms were measured from an isometric mid-thigh pull. Golf performance was assessed in terms of ball launch speed, spin rate, carry yardage, and total yardage, averaged from five shots using a driver. Following training, all measures of strength-power improved, with countermovement jump peak power improving significantly (p < 0.00625). The golf performance assessment indicated significant increases (p < 0.0125) in ball speed, carry yardage, and total yardage. These results suggest that vertically oriented resistance training can improve golf driving performance.

Monitoring external workloads and countermovement jump performance may be useful for coaches. PURPOSE: The purpose of this study was to determine the effects of external load on player performance as measured by a CMJ and specific blood biomarkers throughout the preseason. METHODS:10 female division 1 basketball athletes had PlayerLoadTM (PL) monitored for all mandatory basketball training during six weeks of the preseason and CMJs were performed weekly. Blood biomarkers were collected before preseason and at the end of preseason. Data were analyzed via the Catapult Sport software (Openfield, Catapult, Innovations, Melbourne, VIC, Australia) to quantify all participant movement. Data from CMJs were analyzed via Sparta Science technology (SpartaTrac; SPARTA Performance Science, v1.2.4). Cumulative effect of physical activity (CTPL) was estimated as a sum of total PL up to each jump testing session divided by the number of days. Linear mixed-effects models were used to model data related to the efficacy of PL and CTPL. Athletes (id) and their positions were examined as potential random effects. RESULTS: The best fit model suggested a high-order polynomial pattern between PL and the number of days since the first jump testing session with a random effect for the intercept (marginal R2 = 0.290; conditional R2 = 0.471). The fixed effect for the slope of the first order term was found to be positive. There was a significant negative effect of CTPL on JH (p = 0.0037). The boot strapped model showed a marginal R2 of 0.0183 (95% CI [0.000952, 0.0744]) and a conditional R2 of 0.884 (95% CI [0.762, 0.956]). For RSImod, a significant negative association between RSImod and CTPL (p = 0.0039, 95% CI [-0.0002214, -4.597081e-05]). CONCLUSION: Workloads increase during preseason. CMJ height and RSImod may have limited utility in displaying the effects cumulative workloads. Position played did not impact workload or the impact of that workload on the player. PRACTICAL APPLICATION: Cumulative effect of physical activity may be tracked using CTPL derived from PL. Practitioners may be encouraged to monitor alternative countermovement variables to better understand performance response to the cumulative effect of physical activity.

Team sports frequently use inertial measurement units (IMU) fixed at the scapulae for the quantification of athlete performance. Similar IMU are used in clinical settings for gait analysis and jump testing but are located at the center of mass (COM). For clinical methods of jump and gait analysis to be translated to sports related IMU, an investigation of the validity of measure from the scapulae should be assessed. The objective of the current study was to translate clinical methods of gait analysis and jump assessment to commercially available trunk-mounted accelerometers. The current study created a gait program to analyze and compile the gait data. Following completion of the gait program, the IMU (STATSports APEX) was investigated for validity against ankle accelerometers. Once the validity was determined, an application study evaluated the relevance of collecting gait data during a NCAA D1 Women's Soccer season. Similarly, the trunk-mounted accelerometer was validated against force plates to assess countermovement jump height. The final study assessed how both jump height and gait variables changed due to game-related decline in performance. This study provides evidence that trunk-mounted accelerometers are a valid tool for assessing temporal gait variables (ICCRight = 0.95 and ICCLeft = 0.96), CMJ height (ICCJH = 0.90) and flight time (ICCFT = 0.88). A longitudinal analysis of gait showed that StepL, StrideL, kleg, and postural variables changed regularly in pre-post comparisons of performance. Postural variables had more changes towards the end of the season. Root mean squares (RMS) of accelerations and angular velocities had the highest correlations to High Speed Running (HSR). Fractal step and stride length (StepLα and StrideLα) had the strongest correlation to Total Distance (Rstep = -0.29 and Rstride = -0.29), or Tot Dist. When comparing gait and CMJ analyses to detect game-related changes in performance, CMJ was more descriptive of fatigue. In a proof-of-concept study, pre-post changes in CMJ immediately before and after a game had a moderate negative correlation (R = -0.57) to Tot Dist. When the protocol changed to assess the differences between the days before and after the game, the correlation weakened to R = -0.27. Spatiotemporal and spring mass variables did not change, whereas postural variables appeared to improve. The current study has provided evidence that running gait could be used as an athlete monitoring technique, however more data needs to be collected to understand how running gait variables change with team-sports related fatigue. / Doctor of Philosophy / Trunk-mounted accelerometers have become widely popular in team sports such as soccer. Prior to their use in team sports, accelerometers were used in clinical settings to assess gait, and in some cases jump performance. Different from the trunk-mounted accelerometers, the clinical accelerometers were fixed on the lower back to approximate the position of the center of mass. Consequently, the methods to assess gait and jump performance using an accelerometer assume that the accelerometer is fixed on the lower back. For these methods to be translated to trunk-mounted accelerometers, the validity of the methods needs to be established. This paper investigated the validity of trunk-mounted accelerometers in evaluating gait and countermovement jump height. A season-long assessment of gait provided insight into the utility of monitoring gait in team sports athletes. Lastly, a comparison of gait to countermovement jump analyses helped to elucidate what the changes in gait indicate, and how team staff may effectively utilize that information. The trunk-mounted accelerometer (STATSports APEX) was valid in estimating gait and jump variables. The seasonal analysis showed that gait variables changed frequently throughout the season. The main variables affected described the step and stride length of the individual, the stiffness of the leg, and variables representing the variability in trunk movements associated with running. The variability in trunk movements were more perturbed towards the end of the season when players may be beginning to tire from continuous training and competition. In the final study, the jump analysis proved to be more representative of the player's state of fatigue than gait. The gait variables appeared to improve after exhaustive exercise. The apparent improvement in gait variables could indicate that the players recovered quickly from the exhaustive exercise, or that gait variables respond in a more complex fashion than jump variables. More data needs to be collected on how gait changes due to game-related fatigue in soccer players to better understand its effect on neuromuscular performance.