Kinetic Analysis, Potentiation, and Fatigue During Vertical and Horizontal Plyometric Training: An In-Depth Investigation Into Session Volume.

Despite previous support for plyometric training, optimal dosing strategies remain unclear. PURPOSE: To investigate vertical and horizontal jump kinetic performance following a low-volume plyometric stimulus with progressively increased session jump volume. METHODS: Sixteen academy rugby players (20.0 [2.0] y; 103.0 [17.6] kg; 184.3 [5.5] cm) volunteered for this study. Vertical and horizontal jump sessions were conducted 1 week apart and consisted of a 40-jump low-volume plyometric stimulus using 4 exercises, after which volume was progressively increased to 200 jumps, using countermovement jump (CMJ) for vertical sessions and horizontal broad jump (HBJ) for horizontal sessions. Jump performance was assessed via force-plate analysis at baseline (PRE-0), following the low-volume plyometric stimulus (P-40), and every subsequent 10 jumps until the end of the session (P-50, P-60, P-70, ... P-200). RESULTS: The low-volume stimulus was effective in potentiating HBJ (2% to 5%) but not CMJ (0% to -7%) performance (P < .001). The HBJ performance enhancements were maintained throughout the entire high-volume session, while CMJ realized small but significant decrements (-5% to -7%) in jump height P-50 to P-80 before recovering to presession values. Moreover, increases in eccentric impulse (5% to 24%; P < .001) in both sessions were associated with decreased or maintained concentric impulse, indicating a breakdown in performance-augmenting mechanisms and less effective power transfer concentrically after moderate volumes. CONCLUSION: Practitioners should consider kinetic differences between HBJ and CMJ with increasing volume to better inform and understand session dosing strategies.

The associations between physical-test performance and match performance in women's Rugby Sevens players.

Evaluating the relationships between physical-test and match performance in team sports could be useful for training prescription and athlete evaluation. Here we investigated these relationships in women's Rugby Sevens. Thirty provincial-representative players performed Bronco-fitness, countermovement-jump, acceleration, speed, and strength tests within two weeks before a two-day tournament. Match-running and match-action performance measures were provided by GPS units and video analysis. Generalised and general linear mixed models were employed to estimate the effect of a two standard-deviation difference in physical-test measures on match measures. Effect magnitudes were assessed via standardisation (using the between-player SD) and, for effects on tries scored, also via match winning (based on simulating matches). Evidence for substantial and trivial true magnitudes was provided by one-sided interval-hypothesis tests and Bayesian analysis. There was good evidence of positive effects of many physical-test measures on match high-intensity running, with large effects for jump height and acceleration. There was some evidence of small-moderate positive effects of speed and Bronco, and of small-moderate negative effects of maximal strength and jump height, on match total running and high intensity changes in speed. The evidence was generally inadequate for associations between physical-test measures and match actions, but there was good evidence of small-large positive effects of back squat and jump height on tries scored. Enhancing players' jump height and back-squat performance might therefore increase the likelihood of match success in women's Rugby Sevens.

Operation early-bird: Investigating altered light exposure in military barracks on sleep and performance-a placebo-controlled study.

The manipulation of light exposure in the evening has been shown to modulate sleep, and may be beneficial in a military setting where sleep is reported to be problematic. This study investigated the efficacy of low-temperature lighting on objective sleep measures and physical performance in military trainees. Sixty-four officer-trainees (52 male/12 female, mean ± SD age: 25 ± 5 years) wore wrist-actigraphs for 6 weeks during military training to quantify sleep metrics. Trainee 2.4-km run time and upper-body muscular-endurance were assessed before and after the training course. Participants were randomly assigned to either: low-temperature lighting (LOW, n = 19), standard-temperature lighting with a placebo "sleep-enhancing" device (PLA, n = 17), or standard-temperature lighting (CON, n = 28) groups in their military barracks for the duration of the course. Repeated-measures ANOVAs were run to identify significant differences with post hoc analyses and effect size calculations performed where indicated. No significant interaction effect was observed for the sleep metrics; however, there was a significant effect of time for average sleep duration, and small benefits of LOW when compared with CON (d = 0.41-0.44). A significant interaction was observed for the 2.4-km run, with the improvement in LOW (Δ92.3 s) associated with a large improvement when compared with CON (Δ35.9 s; p = 0.003; d = 0.95 ± 0.60), but not PLA (Δ68.6 s). Similarly, curl-up improvement resulted in a moderate effect in favour of LOW (Δ14 repetitions) compared with CON (Δ6; p = 0.063; d = 0.68 ± 0.72). Chronic exposure to low-temperature lighting was associated with benefits to aerobic fitness across a 6-week training period, with minimal effects on sleep measures.

A Contactless App-Based Intervention to Improve Health Behaviors in Airline Pilots: A Randomized Trial.

INTRODUCTION: There is a need for enhanced preventive health care among airline pilots to mitigate the prevalence of cardiometabolic health risk factors. STUDY DESIGN: A randomized, waitlist-controlled trial was utilized to evaluate the effectiveness of a smartphone-based app intervention for improving health behaviors and cardiometabolic health parameters. SETTING/PARTICIPANTS: A total of 186 airline pilots (aged 43.2±9.1 years; male, 64%) were recruited and participated in the trial during 2022. INTERVENTION: This intervention was a personalized, 16-week smartphone-based app multicomponent physical activity, healthy eating, and sleep hygiene intervention. MAIN OUTCOME MEASURES: Outcome measures of objective health (Cooper's 12-minute exercise test, resting heart rate, push ups, plank isometric hold, body mass), subjective health (self-rated health, perceived psychological stress and fatigue), and health behaviors (weekly physical activity, sleep quality and duration, fruit and vegetable intake) were collected at baseline and after intervention. The waitlist control completed the same measures. RESULTS: Significant interactions for time Χ group from baseline to 16 weeks were found for all outcome measures (p<0.001). Significant between-group differences for positive health changes in favor of the intervention group were found after intervention for all outcome measures (p<0.05, d=0.4-1.0) except for self-rated health, body mass, and Pittsburgh Sleep Quality Index score. CONCLUSIONS: Study findings show that an app-based health behavior intervention can elicit positive cardiometabolic health changes among airline pilots over 16 weeks, associated with trivial to large effect sizes. TRIAL REGISTRATION: The trial protocol was prospectively registered at The Australian New Zealand Clinical Trials Registry (ACTRN12622000288729).

Heating Up to Keep Cool: Benefits and Persistence of a Practical Heat Acclimation Protocol in Elite Female Olympic Team-Sport Athletes.

PURPOSE: Although recommendations for effective heat acclimation (HA) strategies for many circumstances exist, best-practice HA protocols specific to elite female team-sport athletes are yet to be established. Therefore, the authors aimed to investigate the effectiveness and retention of a passive HA protocol integrated in a female Olympic rugby sevens team training program. METHODS: Twelve elite female rugby sevens athletes undertook 10 days of passive HA across 2 training weeks. Tympanic temperature (TTymp), sweat loss, heart rate, and repeated 6-second cycling sprint performance were assessed using a sport-specific heat stress test Pre-HA, after 3 days (Mid-HA), after 10 days (Post-HA), and 15 days post-HA (Decay). RESULTS: Compared with Pre-HA, submaximal TTymp was lower Mid-HA and Post-HA (both by -0.2 [0.7] °C; d ≥ 0.71), while resting TTymp was lower Post-HA (by -0.3 [0.2] °C; d = 0.81). There were no differences in TTymp at Decay compared with Pre-HA, nor were there any differences in heart rate or sweat loss at any time points. Mean peak 6-second power output improved Mid-HA and Post-HA (76 [36] W; 75 [34] W, respectively; d ≥ 0.45) compared with Pre-HA. The observed performance improvement persisted at Decay by 65 (45) W (d = 0.41). CONCLUSIONS: Ten days of passive HA can elicit some thermoregulatory and performance benefits when integrated into a training program in elite female team-sport athletes. However, such a protocol does not provide a sufficient thermal impulse for thermoregulatory adaptations to be retained after 15 days with no further heat stimulus.

A Multidisciplinary Approach to Game Day Preparation for Team Sports: A Delphi Study With Expert Consensus.

ABSTRACT: Mason, BRJ, Pumpa, KL, McKune, AJ, Gill, ND, and Ball, NB. A multidisciplinary approach to game day preparation for team sports: A Delphi study with expert consensus. J Strength Cond Res 36(5): 1345-1352, 2022-The aim of this study was to identify game day preparation strategies used by performance staff to improve team sport performance and to determine consensus regarding the application and importance of these strategies. Twenty-five performance staff working in high performance or professional team sports participated in this Delphi study, which implemented 3 survey rounds. The first round sought responses to open-ended questions relating to the use of game day preparation strategies. These responses were developed into statements and recirculated (round-2 survey), with subjects asked to rate their level of agreement with each statement. The third and final survey presented revised versions of statements that did not reach a consensus in the previous round, along with new statements derived from subject responses. A thematic analysis of the open-ended responses in the first survey identified 5 key themes relating to game day preparation strategies: "exercise," "nutrition," "psychological," "technical and tactical," and "other." The round-2 survey included 38 statements across the 5 themes, with 22 reaching the consensus threshold (≥75%) for agreement. The remaining 16 statements did not reach consensus. The final survey included 18 statements (16 revised and 2 new) with 12 reaching the consensus threshold for agreement. Key preparation strategies identified in this study include structured and progressive warm-ups, strength and power-based priming sessions, individualized nutrition plans, and precooling in hot conditions. Performance staff working in similar environments should consider adopting these strategies to improve athlete or team performance.

Under Pressure: The Chronic Effects of Lower-Body Compression Garment Use during a 6-Week Military Training Course.

Background: Previous studies have shown that compression garments may aid recovery in acute settings; however, less is known about the long-term use of compression garments (CG) for recovery. This study aimed to assess the influence of wearing CG on changes in physical performance, subjective soreness, and sleep quality over 6 weeks of military training. Methods: Fifty-five officer-trainees aged 24 ± 6 y from the New Zealand Defence Force participated in the current study. Twenty-seven participants wore CG every evening for 4−6 h, and twenty-eight wore standard military attire (CON) over a 6-week period. Subjective questionnaires (soreness and sleep quality) were completed weekly, and 2.4 km run time-trial, maximum press-ups, and curl-ups were tested before and after the 6 weeks of military training. Results: Repeated measures ANOVA indicated no significant group × time interactions for performance measures (p > 0.05). However, there were small effects in favour of CG over CON for improvements in 2.4 km run times (d = −0.24) and press-ups (d = 0.36), respectively. Subjective soreness also resulted in no significant group × time interaction but displayed small to moderate effects for reduced soreness in favour of CG. Conclusions: Though not statistically significant, CG provided small to moderate benefits to muscle-soreness and small benefits to aspects of physical-performance over a 6-week military training regime.

The Influence of Full-Time Holistic Support Delivered by a Sports Nutritionist on Within-Day Macronutrient Distribution in New Zealand Provincial Academy Rugby Union Players.

Dietary intake is an important consideration for rugby union ('rugby') players to ensure substrate provision for optimal performance and facilitate recovery. Within-day meal distribution is especially important for athletes, particularly those with congested schedules and multiple daily training sessions. In the present study, 10 provincial academy rugby players engaged in a holistic support protocol informed by behaviour-change techniques led by a full-time sports nutritionist. Dietary intake was estimated during a 4-week monitoring and 4-week intervention period using the remote food photography method on one high-volume training day (two training sessions) and two low-volume training days (≤1 training session) per week. Lean body mass did not change significantly in response to the intervention. Significant increases were observed for protein on both low-volume (breakfast, AM snack, evening snack) and high-volume (post-gym, AM snack, evening snack) training days. Carbohydrate intake post-intervention was significantly greater at the pre-gym eating occasion but lower at PM snack and dinner eating occasions on high-volume days. These data suggest that incorporating a holistic support protocol led by a sports nutritionist can influence within-day nutrient intake in rugby players; however, no change to lean body mass was observed, and the influence of these changes in nutrient intake on performance and recovery warrants further investigation.

Sleep duration and physical performance during a 6-week military training course.

Sleep is vital in influencing effective training adaptations in the military. This study aimed to assess the relationship between sleep and changes in physical performance over 6 weeks of military training. A total of 22 officer-trainees (age: 24 ± 5 years) from the New Zealand Defence Force were used for this prospective cohort study. Participants wore wrist-actigraphs to monitor sleep, completed subjective wellbeing questionnaires weekly, and were tested for: 2.4-km run time-trial, maximum press-up and curl-ups before and after 6 weeks of training. Average sleep duration was calculated over 36 nights (6:10 ± 0:28 hr:min), and sleep duration at the mid-point (6:15 hr:min) was used to stratify the trainees into two quantile groups (UNDERS: 5:51 ± 0:29 hr:min, n = 11) and (OVERS: 6:27 ± 0:09 hr:min, n = 11). There were no significant group × time interactions for 2.4-km run, press-ups or curl-ups (p > .05); however, small effects were observed in favour of OVERS for 2.4-km run (59.8 versus 44.9 s; d = 0.26) and press-ups (4.7 versus 3.2 reps; d = 0.45). Subjective wellbeing scores resulted in a significant group × time interaction (p < .05), with large effect sizes in favour of the OVERS group for Fatigue in Week 1 (d = 0.90) and Week 3 (d = 0.87), and Soreness in Week 3 (d = 1.09) and Week 4 (d = 0.95). Sleeping more than 6:15 hr:min per night over 6 weeks was associated with small benefits to aspects of physical performance, and moderate to large benefits on subjective wellbeing measures when compared with sleeping < 6:15 hr:min.

Horizontal Force-Velocity-Power Profiling of Rugby Players: A Cross-Sectional Analysis of Competition-Level and Position-Specific Movement Demands.

ABSTRACT: Watkins, CM, Storey, A, McGuigan, MR, Downes, P, and Gill, ND. Horizontal force-velocity-power profiling of rugby players: A cross-sectional analysis of competition-level and position-specific movement demands. J Strength Cond Res 35(6): 1576-1585, 2021-Speed and acceleration are crucial to competitive success in all levels of rugby union. However, positional demands affect an athlete's expression of force and velocity during the match. This study investigated maximal sprint performance and horizontal force-velocity (FV) profiles in 176 rugby union players participating in amateur club, professional, and international competitions. Rugby players were divided into 5 positional groups: tight-5 forwards (n = 63), loose forwards (n = 35), inside backs (n = 29), midbacks (n = 22), and outside (n = 27) backs. Sprint performance was averaged across 2 trials of a maximal 30-m sprint, separated by a 3-minute rest. The results demonstrated differences in sprint performance and FV profile characteristics across competitions and positional groups. Specifically, both international and professional players possessed significantly faster split times and superior FV profiles than club players (p < 0.01; effect size [ES]: 0.22-1.42). International players were significantly faster across 0-10 m than professional players (p = 0.03; ES: 0.44-0.47), whereas professional players had faster 10-20 m times (p = 0.03; ES: 0.37-0.41) and a more force-dominant profile (p < 0.01; ES: 0.71-1.00). Across positions, split times decreased and maximal velocity characteristics increased in proportion with increasing positional number, with outside backs being the fastest (ES: 0.38-2.22). On the other hand, both forwards groups had more force-dominant profiles and average sprint momentum across all distances than all backs positions. Interestingly, loose forwards had a more forceful profile and slower 10-, 20-, and 30-m split times but similar maximal velocity characteristics to inside backs, highlighting unique positional demands and physical attributes.

Implementation and Efficacy of Plyometric Training: Bridging the Gap Between Practice and Research.

ABSTRACT: Watkins, CM, Storey, A, McGuigan, M, and Gill, ND. Implementation and efficacy of plyometric training: Bridging the gap between practice and research. J Strength Cond Res 35(5): 1244-1255, 2021-Plyometric training is an effective method for improving speed and acceleration. However, a gap seems to exist between research recommendations and practitioner's actual programs. Some reports suggest as many as 400 jumps per session, while anecdotally some strength and conditioning coaches are using as few as 15-40 jumps even with elite athletes. Thus, the purposes of this study were to obtain a clearer understanding of the practitioner's perspective on plyometric training strategies as compared to literary recommendations and to compare any trends across competition level or sport categories. An integrative mixed-methods model was used. Globally, 61 strength and conditioning practitioners completed an anonymous online survey, containing 5 sections: 1. Sport and coaching background information, 2. Plyometric training focus, 3. Periodization strategy, 4. Plyometric program details, and 5. Efficacy of plyometrics for sport performance. Questions included yes/no, multiple choice, Likert scale, percentage-based, and open-ended questions. The majority (70.5%) of respondents reported regularly implementing plyometric training and overwhelmingly (96.7%) reported positive athlete feedback surrounding its perceived efficacy. Findings confirmed that many practitioners regularly use significantly lower session volumes than previous literary recommendations (p < 0.05). In addition, significant differences were noted in many program details across competition level and sport category including volume periodization, exercise choice, and plyometric intensity. Practitioners may want to reflect on these reported group differences when building training programs best suited for their athletes. Meanwhile, future research should consider these reported perspectives when formulating interventions in attempts of bridging the gap between practice and theory.

The Use of Global Positioning and Accelerometer Systems in Age-Grade and Senior Rugby Union: A Systematic Review.

BACKGROUND: Global positioning systems (GPS) imbedded with accelerometer systems (AS) are used in rugby union (RU) to collect information on absolute and relative distances, distances in different speed zones, high-speed running (HSR) distances, repeated high-intensity efforts (RHIE) and collisions and impacts. This information can be used to monitor match play which can then be used to plan training sessions. The objective of this review was to conduct a systematic review of studies which have reported the use of GPS and AS. METHODS: A systematic review of the use of GPS and AS in both age-grade and senior rugby was conducted. The authors systematically searched electronic databases from January 2010 until March 2020. Keywords included rugby union, GPS, global position* and microtechnology. RESULTS: A total of 51 studies met the eligibility criteria and were included in this review. There was a total of 34 studies utilising GPS and AS in senior RU players (mean ± SD; age 26.2 ± 1.9 years; height 185.7 ± 2.6 cm; mass 101.3 ± 4.2 kg) and 17 studies in age-grade RU players (mean ± SD; age 17.6 ± 1.5 years; height 182.1 ± 3.3 cm; mass 87.1 ± 8.6 kg). The results of this review highlighted that there are differences between backs and forwards and within these positions in these groups during both match play and training sessions. The backs covered greater total absolute, relative and HSR distance compared to forwards. Forwards are involved in more collisions and impacts than backs. When investigating the most intense periods of match play, studies in this review highlighted that the demands during these periods outweigh the average demands of the game. It was proposed that a rolling average over different time epochs is the best way to assess this and ensure that the most intense periods of play are assessed and monitored. CONCLUSIONS: The information highlighted in this review can be used to help coaches assess performances in match play, allow them to plan appropriate training sessions and monitor training load.

The Effect of Low-Volume Preseason Plyometric Training on Force-Velocity Profiles in Semiprofessional Rugby Union Players.

ABSTRACT: Watkins, CM, Gill, ND, Maunder, E, Downes, P, Young, JD, McGuigan, MR, and Storey, AG. The effect of low-volume preseason plyometric training on force-velocity profiles in semiprofessional rugby union players. J Strength Cond Res 35(3): 604-615, 2021-Rugby union is a physically demanding and complex team sport requiring athletes across all positions to express speed and acceleration. Plyometrics can effectively improve speed profiles by enhancing both force- and velocity-(FV) characteristics; however, the optimal dose and exercise direction for trained athletes is still relatively unknown. Therefore, the aim of this investigation was to determine the efficacy of a low-dose, directionally specific plyometric training program for improving speed profiles in semiprofessional rugby players. Players were randomly allocated to one of 2 plyometric training groups that performed low-volume (40-60 ground contacts per session) plyometrics twice weekly, or a control group that did not participate in any plyometric training. The 2 training groups underwent reverse back-to-back three-week vertically and horizontally focused plyometric training programs, with a 12-day washout. Body composition, aerobic capacity, and sprint performance (10-, 20-, 30-m split time, horizontal FV profile) were measured. During the intervention, HV-1 (horizontal/vertical training group 1) improved sprint performance (n = 12; ∆30 m = -0.020 seconds; p = 0.038), VH-2 (vertical/horizontal training group 2) maintained sprint performance (n = 8; ∆30 m = +0.049 seconds; p = 0.377), and the control group progressively declined in sprint performance (n = 12; ∆30 m = +0.071; p = 0.019). In addition, vertical plyometrics may preferentially benefit secondary acceleration (∆10-20 m split time: -0.01 seconds; p = 0.03) and many force-oriented FV profile characteristics. Correlational analyses (r2 = -0.568 to 0.515) showed sprint improvements were hindered in athletes with lower initial aerobic fitness, suggesting accumulated fatigue may have limited the magnitude of adaptation. Therefore, including low-volume plyometric training may be beneficial for improving sprint profiles or attenuating decrements realized during periods of high-volume sport-specific training.

Match Demands, Anthropometric Characteristics, and Physical Qualities of Female Rugby Sevens Athletes: A Systematic Review.

Sella, FS, McMaster, DT, Beaven, CM, Gill, ND, and Hébert-Losier, K. Match demands, anthropometric characteristics, and physical qualities of female rugby sevens athletes: A systematic review. J Strength Cond Res 33(12): 3463-3474, 2019-Since the inclusion of rugby sevens in the 2016 Olympic Games, the popularity of women's rugby sevens has grown rapidly worldwide. This systematic review aimed to summarize the scientific literature addressing the match demands, anthropometric characteristics, and physical qualities of female rugby sevens athletes and to highlight differences between competition levels and playing positions. Four electronic databases were searched, as were the reference lists and key journals. Hedges' g effect sizes with 95% confidence intervals were calculated to evaluate differences between elite and nonelite athletes, and backs and forwards. Twenty-seven studies met inclusion criteria and scored 68 ± 13% upon quality assessment. Comparisons between groups were restricted to variables where data were available. Greater running demands and intensities, number of sprints and accelerations, but lower physiological responses characterized international matches compared with nationals. At international level, backs demonstrated greater running demands and intensities, number of sprints, and physiological responses than forwards. Elite athletes were leaner, taller, and displayed superior physical qualities (e.g., maximal speed, power, upper-body strength, and aerobic capacity) compared with nonelite athletes. At elite level, forwards were heavier and displayed greater upper-body strength, whereas backs showed greater acceleration and maximal speed abilities. The specific match demands and physical requirements of female rugby sevens athletes competing at different playing levels and playing positions must be considered for developing effective training programs.

Physical and Physiological Demands of Elite Rugby Union Officials.

PURPOSE: To examine the movement and physiological demands of rugby union officiating in elite competition. METHODS: Movement demands of 9 elite officials across 12 Super Rugby matches were calculated, using global positioning system devices. Total distance (in m), relative distance (in m·min-1), and percentage time spent in various speed zones were calculated across a match. Heart-rate (HR) responses were also recorded throughout each match. Cohen d effect sizes were reported to examine the within-match variations. RESULTS: The total distance covered was 8030 (506) m, with a relative distance of 83 (5) m·min-1 and with no differences observed between halves. Most game time was spent at lower movement speeds (76% [2%]; <2.0 m·s-1), with large effects for time spent >7.0 m·s-1 between halves (d = 2.85). Mean HR was 154 (10) beats·min-1 (83.8 [2.9]%HRmax), with no differences observed between the first and second halves. Most game time was spent between 81%HRmax and 90%HRmax (40.5% [7.5%]) with no observable differences between halves. Distances covered above 5.1 m·s-1 were highest during the first 10 min of a match, while distance at speeds 3.7 to 5 m·s-1 decreased during the final 10 min of play. CONCLUSIONS: These findings highlight the highly demanding and intermittent nature of rugby union officiating, with only some minor variations in physical and physiological demands across a match. These results have implications for the physical preparation of professional rugby union referees.

No Effect of Muscle Stretching within a Full, Dynamic Warm-up on Athletic Performance.

PURPOSE: This study aimed to examine the effects of static and dynamic stretching routines performed as part of a comprehensive warm-up on flexibility and sprint running, jumping, and change of direction tests in team sport athletes. METHODS: A randomized, controlled, crossover study design with experimenter blinding was conducted. On separate days, 20 male team sport athletes completed a comprehensive warm-up routine. After a low-intensity warm-up, a 5-s static stretch (5S), a 30-s static stretch (30S; 3 × 10-s stretches), a 5-repetition (per muscle group) dynamic stretch (DYN), or a no-stretch (NS) protocol was completed; stretches were done on seven lower body and two upper body regions. This was followed by test-specific practice progressing to maximum intensity. A comprehensive test battery assessing intervention effect expectations as well as flexibility, vertical jump, sprint running, and change of direction outcomes was then completed in a random order. RESULTS: There were no effects of stretch condition on test performances. Before the study, 18/20 participants nominated DYN as the most likely to improve performance and 15/20 nominated NS as least likely. Immediately before testing, NS was rated less "effective" (4.0 ± 2.2 on a 10-point scale) than 5S, 30S, and DYN (5.3-6.4). Nonetheless, these ratings were not related to test performances. CONCLUSION: Participants felt they were more likely to perform well when stretching was performed as part of the warm-up, irrespective of stretch type. However, no effect of muscle stretching was observed on flexibility and physical function compared with no stretching. On the basis of the current evidence, the inclusion of short durations of either static or dynamic stretching is unlikely to affect sprint running, jumping, or change of direction performance when performed as part of a comprehensive physical preparation routine.

Relationships Between Concentric and Eccentric Strength and Countermovement Jump Performance in Resistance Trained Men.

Bridgeman, LA, McGuigan, MR, Gill, ND, and Dulson, DK. Relationships between concentric and eccentric strength and countermovement jump performance in resistance trained men. J Strength Cond Res 32(1): 255-260, 2018-The purpose of this study was to investigate the relationships between concentric and eccentric peak force (PF) and countermovement jump (CMJ) performance in resistance trained men. Subjects were 12 men (mean ± SD; age: 25.4 ± 3.5 years; height: 177.2 ± 4.5 cm; mass: 84.0 ± 10.1 kg). The men were tested for concentric and eccentric PF using the Exerbotics squat device. Subjects then completed 3 CMJs to allow for the calculation of peak power (PP), peak ground reaction force, and jump height (JH). Correlations between the variables of interest were calculated using Pearson product-moment correlation coefficients. A large relationship was found between absolute concentric PF and absolute CMJ PP (r = 0.66, p ≤ 0.05). Absolute eccentric PF had a very large relationship with absolute CMJ PP and CMJ JH (r = 0.74, p < 0.01 and r = 0.74, p < 0.001, respectively). In addition, absolute eccentric PF was found to have a moderate relationship with relative CMJ PP (r = 0.58, p ≤ 0.05). Relative eccentric PF was had a very large relationship with relative CMJ PP and CMJ JH (r = 0.73, p < 0.001 and r = 0.79, p < 0.001, respectively). Based on these findings, strength and conditioning coaches and athletes who wish to enhance CMJ performance may wish to include exercises, which enhance lower-body eccentric strength within their training.

The Effects of Accentuated Eccentric Loading on the Drop Jump Exercise and the Subsequent Postactivation Potentiation Response.

The aims of this study were (a) to investigate the acute effects of different drop jump (DJ) accentuated eccentric loading (AEL) protocols and (b) to investigate the effect of these AEL DJ protocols on subsequent countermovement jump (CMJ) performance. The subjects were 12 strength-trained athletes; initially, baseline CMJ performance was assessed and individual optimal DJ drop height identified. In subsequent weeks, subjects completed 1 set of 5 DJs with no additional load or an AEL of 10, 20, or 30% of their individual body mass (BM) using dumbbells to provide the extra load. After the AEL DJ protocols, 3 CMJs were completed after 2, 6, and 12 minutes rest. A generalized linear mixed model was used to investigate the effects of AEL load and time post-DJs on CMJ height, peak power, and ground reaction force. The 20% AEL condition resulted in greater CMJ height in comparison with all other conditions (p < 0.001). CMJ height was significantly greater after 2 and 6 minutes rest compared with 12 minutes (p < 0.001 and p ≤ 0.05 respectively). Greater peak power was also found during the CMJs after the 20% AEL condition compared with baseline, BM, and 10% AEL (p ≤ 0.05). In conclusion, 5 DJs with 20% AEL followed by a 2 minutes recovery period resulted in significant enhancement in CMJ height and peak power.

The Effect of Exercise-Induced Muscle Damage After a Bout of Accentuated Eccentric Load Drop Jumps and the Repeated Bout Effect.

Bridgeman, LA, Gill, ND, Dulson, DK, and McGuigan, MR. The effect of exercise induced muscle damage after a bout of accentuated eccentric load drop jumps and the repeated bout effect. J Strength Cond Res 31(2): 386-394, 2017-Although previous studies have investigated exercise-induced muscle damage (EIMD) after a bout of unloaded drop jumps (DJs), none have investigated the effects of accentuated eccentric load (AEL) DJs on EIMD. The purpose of this study was to investigate the effects of 30 and 50 AEL DJs on strength, jump performance, muscle soreness, and blood markers. Eight resistance trained athletes participated in this study. In week 1, baseline countermovement jump (CMJ), squat jump (SJ), concentric and eccentric peak force (PF), creatine kinase, and muscle soreness were assessed. Subjects then completed 30 AEL DJs and baseline measures were retested immediately postintervention, 1, 24, and 48 hours later. Two weeks later, the subjects completed the same protocol with an increase in AEL DJ volume (50). Subjects' SJ height was reduced in week 1 compared with week 3, postintervention, 1, 24, and 48 hours later (ES = -0.34, -0.44, -0.38, and -0.40). Subjects' CMJ height was reduced in week 1 compared with week 3, postintervention, 1, and 24 hours later (ES = -0.37, -0.29, and -0.39). Concentric PF was reduced in week 1 compared with week 3, postintervention and 24 and 48 hours later (ES = -0.02, -0.23, and -0.32). Eccentric PF was reduced in week 1 compared with week 3, postintervention, 24, and 48 hours later (ES = -0.24, -0.16, and -0.50). In this sample, 30 AEL DJs attenuated the effects of EIMD following which 50 AEL DJs completed 2 weeks later.

Test-Retest Reliability of a Novel Isokinetic Squat Device With Strength-Trained Athletes.

Bridgeman, LA, McGuigan, MR, Gill, ND, and Dulson, DK. Test-retest reliability of a novel isokinetic squat device with strength-trained athletes. J Strength Cond Res 30(11): 3261-3265, 2016-The aim of this study was to investigate the test-retest reliability of a novel multijoint isokinetic squat device. The subjects in this study were 10 strength-trained athletes. Each subject completed 3 maximal testing sessions to assess peak concentric and eccentric force (N) over a 3-week period using the Exerbotics squat device. Mean differences between eccentric and concentric force across the trials were calculated. Intraclass correlation coefficients (ICCs) and coefficients of variation (CVs) for the variables of interest were calculated using an excel reliability spreadsheet. Between trials 1 and 2 an 11.0 and 2.3% increase in mean concentric and eccentric forces, respectively, was reported. Between trials 2 and 3 a 1.35% increase in the mean concentric force production and a 1.4% increase in eccentric force production was reported. The mean concentric peak force CV and ICC across the 3 trials was 10% (7.6-15.4) and 0.95 (0.87-0.98) respectively. However, the mean eccentric peak force CV and ICC across the trials was 7.2% (5.5-11.1) and 0.90 (0.76-0.97), respectively. Based on these findings it is suggested that the Exerbotics squat device shows good test-retest reliability. Therefore practitioners and investigators may consider its use to monitor changes in concentric and eccentric peak force.