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Purpose: This meta-analysis aimed to (1) provide a comparison of peak changes in indirect markers of exercise-induced muscle damage (EIMD) in youths versus adults and (2) determine if the involved limb moderated this effect. Method: Studies were eligible for inclusion if they (1) provided a human youth versus adult comparison; (2) provided data on muscle strength, soreness, or creatine kinase markers beyond ≥24 hours; and (3) did not provide a recovery treatment. Effect sizes (ES) were presented alongside 95% confidence intervals. Results: EIMD exhibited larger effects on adults than in youths for muscle strength (ES = −2.01; P <.001), muscle soreness (ES = −1.52; P <.001), and creatine kinase (ES = −1.98; P <.001). The random effects meta-regression indicated that the effects of upper- and lower-limb exercise in youths and adults were significant for muscle soreness (coefficient estimate = 1.11; P <.001) but not for muscle strength or creatine kinase (P >.05). As such, the between-group effects for muscle soreness (ES = −2.10 vs −1.03; P <.05) were greater in the upper than lower limbs. Conclusion: The magnitude of EIMD in youths is substantially less than in their adult counterparts, and this effect is greater in upper than lower limbs for muscle soreness. These findings help guide practitioners who may be concerned about the potential impact of EIMD when training youth athletes. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this study were to examine the variability of selected external load metrics within 15-minute intervals during soccer match play and examine their relationship with players' high-intensity intermittent fitness. Methods: A total of 18 male soccer players were monitored for their external load metrics during 26 matches, which included total distance, high-metabolic-load distance, and mechanical work (defined as the sum of accelerations and decelerations >3 m2). Additionally, players completed the 30-15 Intermittent Fitness Test. Results: Total distance had lower coefficients of variation than high-metabolic-load distance and mechanical work (effect size [ES]: 5.2 to 6.4; very large). Within-player Δ-15min showed moderate to large decreases (ES: −0.7 to −1.6) and increases (ES: 0.9 to 1.8) in absolute and coefficient-of-variation values, respectively. Large relationships (r =.55 to.61) were observed between the Intermittent Fitness Test and 15-minmean and 15-minbest in all selected external load metrics. However, small to moderate (0.27 to 0.41) associations were observed between the Intermittent Fitness Test and Δ-15min in selected external load metrics. Conclusions: These findings suggest that players with relatively lower intermittent running capacity might show lower variability during matches, as evidenced by smaller reductions in high-intensity actions during the final 15 minutes. We attribute these observations to players' possessing better pacing strategies. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to examine the physical match profiles of professional soccer players using 3 and 5 min fixed and rolling averages as well as fixed 1 min averages, with considerations to training prescription. Methods: Twenty-nine professional U23 soccer outfield players competed across 17 competitive matches during the 2017/18 season, equating to a total of 130 separate physical match profiles. Match activities were recorded using global positioning system (GPS) devices with integrated micro-electrical mechanical systems (MEMS), recording total distance (TD), high-speed running (HSR), and metabolic power (MP). For each individual match profile and variable, 1, 3, and 5 min peak, post-peak, and average values were calculated using fixed-time epochs (FIXED) and rolling averages (ROLL). Linear mixed models were employed to examine the differences in the dependent variables as a function of the method of measurement. Results: Results revealed significantly higher peak values, for relative TD, relative HSR and relative MP when employing the ROLL sampling method, in comparison to the FIXED method, for both 3 min and 5 min epoch lengths. Analysis of epoch length revealed significantly higher peak values, across all positions, for relative TD, relative HSR and MP for 1 min epochs, in comparison to 3 min and 5 min epochs. Conclusions: The data offers a novel insight into the appropriate identification of physical demands during youth soccer match-play. Researchers and practitioners should consider the sampling method and epoch length when assessing the physical demands of competitive match-play, as well as when designing and prescribing sport-specific conditioning drills.

Purpose: We examined the movement, physiological and muscle function responses to running with and without (i.e. linear) multiple directional changes to understand which measures of external demands better reflected changes in the internal response. Methods: Twelve team sport athletes completed a linear and multidirectional running trial during which movement characteristics, oxygen consumption (V_O2), blood lactate (B[La]) and heart rate (HR) were measured. Isometric peak torque of knee extensors and flexors was also assessed before and after each trial. Results: High speed running distance was higher during the linear trial (p < 0.001), whereas time at high metabolic power (p = 0.046), number of accelerations (p < 0.001), summated HR (p = 0.003) and B[La] (p = 0.002) were higher during the multidirectional trial. Integrated external to internal ratios of high-speed running: summated HR and highspeed running: total VO2 were different between multidirectional and linear trials (p = 0.001). Conversely, high metabolic power: summated HR and high metabolic power: total V_O2 were similar (p = 0.246). Small decrements in knee flexor (p = 0.003) and extensor torque (p = 0.004) were observed after both trials. Conclusion: Time at high metabolic power better reflects the increased internal response during running with more directional changes than high speed running. [ABSTRACT FROM AUTHOR]

Aging is anecdotally associated with a prolonged recovery from resistance training, though current literature remains equivocal. This brief review considers the effects of resistance training on indirect markers of muscle damage and recovery (i.e., muscle soreness, blood markers, and muscle strength) in older males. With no date restrictions, four databases were searched for articles relating to aging, muscle damage, and recovery. Data from 11 studies were extracted for review. Of these, four reported worse symptoms in older compared with younger populations, while two have observed the opposite, and the remaining studies (n = 6) proposed no differences between age groups. It appears that resistance training can be practiced in older populations without concern for impaired recovery. To improve current knowledge, researchers are urged to utilize more ecologically valid muscle-damaging bouts and investigate the mechanisms which underpin the recovery of muscle soreness and strength after exercise in older populations. [ABSTRACT FROM AUTHOR]

Purpose: To identify the association between several contextual match factors, technical performance, and external movement demands on the subjective task load of elite rugby league players. Methods: Individual subjective task load, quantified using the National Aeronautics and Space Administration Task Load Index (NASA-TLX), was collected from 29 professional rugby league players from one club competing in the European Super League throughout the 2017 season. The sample consisted of 26 matches (441 individual data points). Linear mixed modeling revealed that various combinations of contextual factors, technical performance, and movement demands were associated with subjective task load. Results: Greater number of tackles (effect size correlation ± 90% confidence intervals; η2 =.18 ±.11), errors (η2 =.15 ±.08), decelerations (η2 =.12 ±.08), increased sprint distance (η2 =.13 ±.08), losing matches (η2 =.36 ±.08), and increased perception of effort (η2 =.27 ±.08) led to most likely–very likely increases in subjective total task load. The independent variables included in the final model for subjective mental demand (match outcome, time played, and number of accelerations) were unclear, excluding a likely small correlation with technical errors (η2 =.10 ±.08). Conclusions: These data provide a greater understanding of the subjective task load and their association with several contextual factors, technical performance, and external movement demands during rugby league competition. Practitioners could use this detailed quantification of internal loads to inform recovery sessions and current training practices. [ABSTRACT FROM AUTHOR]

Purpose: To examine responses to a simulated rugby league protocol designed to include more stochastic commands, and therefore require greater vigilance, than traditional team-sport simulation protocols. Methods: Eleven male university rugby players completed 2 trials (randomized and control [CON]) of a rugby league movement simulation protocol, separated by 7 to 10 d. The CON trial consisted of 48 repeated ∼115-s cycles of activity. The stochastic simulation (STOCH) was matched for the number and types of activity performed every 5.45 min in CON but included no repeated cycles of activity. Movement using GPS, heart rate, rating of perceived exertion, and Stroop test performance was assessed throughout. Maximum voluntary contraction peak torque, voluntary activation (in percentage), and global task load were assessed after exercise. Results: The mean mental demand of STOCH was higher than CON (effect size [ES] = 0.56; ±0.69). Mean sprint speed was higher in STOCH (22.5 [1.4] vs 21.6 [1.6] km·h−1, ES = 0.50; ±0.55), which was accompanied by a higher rating of perceived exertion (14.3 [1.0] vs 13.0 [1.4], ES = 0.87; ±0.67) and a greater number of errors in the Stroop test (10.3 [2.5] vs 9.3 [1.4] errors; ES = 0.65; ±0.83). Maximum voluntary contraction peak torque (CON = −48.4 [31.6] N·m and STOCH = −39.6 [36.6] N·m) and voluntary activation (CON = −8.3% [4.8%] and STOCH = −6.0% [4.1%]) was similarly reduced in both trials. Conclusions: Providing more stochastic commands, which requires greater vigilance, might alter performance and associated physiological, perceptual, and cognitive responses to team-sport simulations. [ABSTRACT FROM AUTHOR]

Purpose: To examine the within- and between-sexes physical performance, well-being, and neuromuscular function responses across a 4-day international touch rugby (Touch) tournament. Methods: Twenty-one males and 20 females completed measures of well-being (fatigue, soreness, sleep, mood, and stress) and neuromuscular function (countermovement jump height, peak power output, and peak force) during a 4-day tournament with internal, external, and perceptual loads recorded for all matches. Results: Relative and absolute total, low-intensity (females), and high-intensity distance were lower on day 3 (males and females) (effect size [ES] = −0.37 to −0.71) compared with day 1. Mean heart rate was possibly to most likely lower during the tournament (except day 2 males; ES = −0.36 to −0.74), whereas rating of perceived exertion-training load was consistently higher in females (ES = 0.02 to 0.83). The change in mean fatigue, soreness, and overall well-being was unclear to most likely lower (ES = −0.33 to −1.90) across the tournament for both sexes, with greater perceived fatigue and soreness in females on days 3 to 4 (ES = 0.39 to 0.78). Jump height and peak power output were possibly to most likely lower across days 2 to 4 (ES = −0.30 to −0.84), with greater reductions in females (ES = 0.21 to 0.66). Well-being, countermovement jump height, and peak force were associated with changes in external, internal, and perceptual measures of load across the tournament (η2 = −.37 to.39). Conclusions: Elite Touch players experience reductions in well-being, neuromuscular function, and running performance across a 4-day tournament, with notable differences in fatigue and running between males and females, suggesting that sex-specific monitoring and intervention strategies are necessary. [ABSTRACT FROM AUTHOR]

Purpose: To determine the utility of running-only and rugby-specific, in-season sprint interval interventions in professional rugby league players. Methods: Thirty-one professional academy rugby players were assigned to a rugby-specific (SITr/s, n = 16) or running-only (SITr, n = 15) sprint interval training group. Measures of speed, power, change of direction ability, prone Yo-Yo Intermittent Recovery Test (Yo-Yo IR1) performance, and heart rate recovery were taken before and after the 2-week intervention as were submaximal responses to the prone Yo-Yo IR1. Internal, external, and perceptual responses were collected during SITr/s and SITr, with well-being and neuromuscular function assessed before each session. Results: Despite contrasting (possible to most likely) internal, external, and perceptual responses to the SIT interventions, possible to most likely within-group improvements in physical characteristics, heart rate recovery, and submaximal responses to the prone Yo-Yo IR1 were observed after both interventions. Between-group analysis favored the SITr/s intervention (trivial to moderate) for changes in 10-m sprint time, countermovement jump, change of direction, and medicine ball throw as well as submaximal (280–440 m) high metabolic power, PlayerLoad™, and acceleration distance during the prone Yo-Yo IR1. Overall changes in well-being or neuromuscular function were unclear. Conclusions: Two weeks of SITr/s and SITr were effective for improving physical characteristics, heart rate recovery, and submaximal responses to the prone Yo-Yo IR1, with no clear change in well-being and neuromuscular function. Between-group analysis favored the SITr/s group, suggesting that the inclusion of sport-specific actions should be considered for in-season conditioning of rugby league players. [ABSTRACT FROM AUTHOR]

Body mass index (BMI) is increasingly recognized as an inadequate measure for determining obesity in children. Therefore, the aim within this study was to investigate other indirect methods of body fat assessment that could potentially be used in place of BMI. Twenty-four children (boys: 13.8 [plus or minus] 0.8 yr; girls: 13.3 [plus or minus] 0.5 yr) participated in this study. Measurements of BMI and waist-to-hip ratio (WHR) were obtained, along with percentage body fat (%BF) from skinfolds (SKF), bioelectrical impedance analysis (BIA) (arm-to-arm, leg-to-leg, arm-to-leg) and air displacement plethysmography (ADP). BMI was correlated with %BF from ADP (r = 0.45, p less than 0.05), while WHR was not (r = 0.21, p greater than 0.05). %BF from the SKF method and all BIA methods demonstrated a significant relationship with ADP %BF (p less than 0.05). The 95% limits of agreement (LoA) indicated that individual prediction errors between all BIA methods and ADP were large, while the SKF method showed strong agreement with ADP. The results of this study provide further evidence that the predictive accuracy of indirect methods for determining body fatness varies considerably with children. The findings are discussed in relation to the National Child Measurement Programme (NCMP), which is currently operating in primary schools in England. (Contains 1 table and 1 figure.)