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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.

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.

Exercise-induced muscle damage (EIMD) is characterized by symptoms that present both immediately and for up to 14 days after the initial exercise bout. The main consequence of EIMD for the athlete is the loss of skeletal muscle function and soreness. As such, numerous nutrients and functional foods have been examined for their potential to ameliorate the effects of EIMD and accelerate recovery, which is the purpose of many nutritional strategies for the athlete. However, the trade-off between recovery and adaptation is rarely considered. For example, many nutritional interventions described in this review target oxidative stress and inflammation, both thought to contribute to EIMD but are also crucial for the recovery and adaptation process. This calls into question whether long term administration of supplements and functional foods used to target EIMD is indeed best practice. This rapidly growing area of sports nutrition will benefit from careful consideration of the potential hormetic effect of long term use of nutritional aids that ameliorate muscle damage. This review provides a concise overview of what EIMD is, its causes and consequences and critically evaluates potential nutritional strategies to ameliorate EIMD. We present a pragmatic practical summary that can be adopted by practitioners and direct future research, with the purpose of pushing the field to better consider the fine balance between recovery and adaptation and the potential that nutritional interventions have in modulating this balance.

Fernandes, JFT, Lamb, KL, and Twist, C. A comparison of load-velocity and load-power relationships between well-trained young and middle-aged males during 3 popular resistance exercises. J Strength Cond Res 32(5): 1440-1447, 2018-This study examined the load-velocity and load-power relationships among 20 young (age 21.0 ± 1.6 years) and 20 middle-aged (age 42.6 ± 6.7 years) resistance-trained males. Participants performed 3 repetitions of bench press, squat, and bent-over-row across a range of loads corresponding to 20-80% of 1 repetition maximum (1RM). Analysis revealed effects (p < 0.05) of group and load × group on barbell velocity for all 3 exercises, and interaction effects on power for squat and bent-over-row (p < 0.05). For bench press and bent-over-row, the young group produced higher barbell velocities, with the magnitude of the differences decreasing as load increased (ES; effect size 0.0-1.7 and 1.0-2.0, respectively). Squat velocity was higher in the young group than the middle-aged group (ES 1.0-1.7) across all loads, as was power for each exercise (ES 1.0-2.3). For all 3 exercises, both velocity and 1RM were correlated with optimal power in the middle-aged group (r = 0.613-0.825, p < 0.05), but only 1RM was correlated with optimal power (r = 0.708-0.867, p < 0.05) in the young group. These findings indicate that despite their resistance training, middle-aged males were unable to achieve velocities at low external loads and power outputs as high as the young males across a range of external resistances. Moreover, the strong correlations between 1RM and velocity with optimal power suggest that middle-aged males would benefit from training methods which maximize these adaptations.

Godwin, MS, Fernandes, JFT, and Twist, C. Effects of variable resistance using chains on bench throw performance in trained rugby players. J Strength Cond Res 32(4): 950-954, 2018-This study sought to determine the effects of variable resistance using chain resistance on bench throw performance. Eight male rugby union players (19.4 ± 2.3 years, 88.8 ± 6.0 kg, 1RM 105.6 ± 17.0 kg) were recruited from a national league team. In a randomized crossover design, participant's performed 3 bench throws at 45% one repetition maximum (1RM) at a constant load (no chains) or a variable load (30% 1RM constant load and 15% 1RM variable load; chains) with 7 days between conditions. For each repetition, the peak and mean velocity, peak power, peak acceleration, and time to peak velocity were recorded. Differences in peak and mean power were very likely trivial and unclear between the chain and no chain conditions, respectively. Possibly greater peak and likely greater mean bar velocity were accompanied by likely to most likely greater bar velocity between 50 and 400 ms from initiation of bench press in the chain condition compared with the no chain condition. Accordingly, bar acceleration was very likely greater in the chain condition compared with the no chain condition. In conclusion, these results show that the inclusion of chain resistance can acutely enhance several variables in the bench press throw and gives support to this type of training.

Till, K, Morris, R, Stokes, K, Trewartha, G, Twist, C, Dobbin, N, Hunwicks, R, and Jones, B. Validity of an isometric midthigh pull dynamometer in male youth athletes. J Strength Cond Res 32(2): 490-493, 2018-The purpose of this study was to investigate the validity of an isometric midthigh pull dynamometer against a criterion measure (i.e., 1,000-Hz force platform) for assessing muscle strength in male youth athletes. Twenty-two male adolescent (age 15.3 ± 0.5 years) rugby league players performed 4 isometric midthigh pull efforts (i.e., 2 on the dynamometer and 2 on the force platform) separated by 5-minute rest in a randomized and counterbalanced order. Mean bias, typical error of estimate (TEE), and Pearson correlation coefficient for peak force (PF) and peak force minus body weight (PFBW) from the force platform were validated against peak force from the dynamometer (DynoPF). When compared with PF and PFBW, mean bias (with 90% confidence limits) for DynoPF was very large (-32.4 [-34.2 to -30.6] %) and moderate (-10.0 [-12.8 to -7.2] %), respectively. The TEE was moderate for both PF (8.1 [6.3-11.2] %) and PFBW (8.9 [7.0-12.4]). Correlations between DynoPF and PF (r 0.90 [0.79-0.95]) and PFBW (r 0.90 [0.80-0.95]) were nearly perfect. The isometric midthigh pull assessed using a dynamometer underestimated PF and PFBW obtained using a criterion force platform. However, strong correlations between the dynamometer and force platform suggest that a dynamometer provides an appropriate alternative to assess isometric midthigh pull strength when a force platform is not available. Therefore, practitioners can use an isometric midthigh pull dynamometer to assess strength in the field with youth athletes but should be aware that it underestimates peak force.

Objectives: The metabolic requirements of a rugby league match simulation protocol and the timing of carbohydrate provision on glycogen re-synthesis in damaged muscle were examined., Design: Fifteen (mean±SD: age 20.9±2.9 year, body-mass 87.3±14.1kg, height 177.4±6.0cm) rugby league (RL) players consumed a 6gkgday-1 CHO diet for 7-days, completed a time to exhaustion test (TTE) and a glycogen depletion protocol on day-3, a RL simulated-match protocol (RLMSP) on day-5 and a TTE on day-7. Players were prescribed an immediate or delayed (2-h-post) re-feed post-simulation., Methods: Muscle biopsies and blood samples were obtained post-depletion, before and after simulated match-play, and 48-h after match-play with PlayerLoad and heart-rate collected throughout the simulation. Data were analysed using effects sizes±90% CI and magnitude-based inferences., Results: PlayerLoad (8.0±0.7 AUmin-1) and %HRpeak (83±4.9%) during the simulation were similar to values reported for RL match-play. Muscle glycogen very likely increased from immediately after to 48-h post-simulation (272±97 cf. 416±162mmolkg-1d.w.; ES±90%CI) after immediate re-feed, but changes were unclear (283±68 cf. 361±144mmolkg-1d.w.; ES±90%CI) after delayed re-feed. CK almost certainly increased by 77.9±25.4% (0.75±0.19) post-simulation for all players., Conclusions: The RLMSP presents a replication of the internal loads associated with professional RL match-play, although difficulties in replicating the collision reduced the metabolic demands and glycogen utilisation. Further, it is possible to replete muscle glycogen in damaged muscle employing an immediate re-feed strategy., (Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

Objectives: Although the physical demands of Rugby League (RL) match-play are well-known, the fuel sources supporting energy-production are poorly understood. We therefore assessed muscle glycogen utilisation and plasma metabolite responses to RL match-play after a relatively high (HCHO) or relatively low CHO (LCHO) diet., Design: Sixteen (mean±SD age; 18±1 years, body-mass; 88±12kg, height 180±8cm) professional players completed a RL match after 36-h consuming a non-isocaloric high carbohydrate (n=8; 6gkgday -1 ) or low carbohydrate (n=8; 3gkgday -1 ) diet., Methods: Muscle biopsies and blood samples were obtained pre- and post-match, alongside external and internal loads quantified using Global Positioning System technology and heart rate, respectively. Data were analysed using effects sizes ±90% CI and magnitude-based inferences., Results: Differences in pre-match muscle glycogen between high and low carbohydrate conditions (449±51 and 444±81mmolkg -1 d.w.) were unclear. High (243±43mmolkg -1 d.w.) and low carbohydrate groups (298±130mmolkg -1 d.w.) were most and very likely reduced post-match, respectively. For both groups, differences in pre-match NEFA and glycerol were unclear, with a most likely increase in NEFA and glycerol post-match. NEFA was likely lower in the high compared with low carbohydrate group post-match (0.95±0.39mmoll -1 and 1.45±0.51mmoll -1 , respectively), whereas differences between the 2 groups for glycerol were unclear (98.1±33.6mmoll -1 and 123.1±39.6mmoll -1 ) in the high and low carbohydrate groups, respectively., Conclusions: Professional RL players can utilise ∼40% of their muscle glycogen during a competitive match regardless of their carbohydrate consumption in the preceding 36-h., (Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate how the type of contact influences physiological, perceptual and locomotive load during a simulated rugby league match. Eleven male university rugby league players performed two trials of the rugby league movement simulation protocol for interchange forwards with a traditional soft tackle bag and a weighted tackle sled to replicate contact demands. The interchange forward-specific simulation was chosen given the contact frequency is higher for this group of players compared to whole match players. Locomotive rate, sprint speed, tackle intensity, heart rate (HR) and rating of perceived exertion were analysed during the first and second bouts that replicated two ~23 min on-field passages. Countermovement jump (CMJ) was measured before and immediately after each trial. More time was spent in heart rate zone between 91 and 100% HRpeak during the first (effect size ± 90% confidence interval: 0.44 ± 0.49) and second bouts (0.44 ± 0.43), and larger (0.6 ± 0.69) decrements in CMJ performance were observed during the sled trial (5.9, s = 4.9%) compared to the bag trial (2.6, s = 5.4%). Changing the type of contact during the match simulation subtly altered both the internal and external loads on participants. Using a standard tackle bag results in faster sprint speed to contact, but lower overall high-intensity running. Conversely, a heavier tackle object increases the internal load and results in greater lower limb neuromuscular fatigue as reflected by the decrease in CMJ performance.

Purpose: While exercise-induced muscle damage (EIMD) after rugby league match play has been well documented, the specific match actions that contribute to EIMD are unclear. Accordingly, the purpose of this study was to investigate the positional demands of elite rugby league matches and examine their relationship with subsequent EIMD., Methods: Twenty-eight performances (from 17 participants) were captured using 10-Hz global positioning systems over 4 competitive matches. Upper- and lower-body neuromuscular fatigue, creatine kinase (CK), and perceived muscle soreness were assessed 24 h before and at 12, 36, and 60 h after matches., Results: High-intensity running was moderately higher in backs (6.6 ± 2.6 m/min) than in forwards (5.1 ± 1.6 m/min), whereas total collisions were moderately lower (31.1 ± 13.1 vs 54.1 ± 37.0). Duration (r = .90, CI: .77-.96) and total (r = .86, CI: .70-.95) and high-intensity distance covered (r = .76, CI: .51-.91) were associated (P < .05) with increased CK concentration postmatch. Total collisions and repeated high-intensity efforts were associated (P < .05) with large decrements in upper-body neuromuscular performance (r = -.48, CI: -.74 to .02; r = -.49, CI: -.77 to .05, respectively), muscle soreness (r = -.68, CI: -.87 to -.10, r = -.66, CI: -.89 to .21, respectively), and CK concentration (r = .67, CI: .42-.85; r = .73, CI: .51-.87, respectively). All EIMD markers returned to baseline within 60 h., Conclusion: Match duration, high-intensity running, and collisions were associated with variations in EIMD markers, suggesting that recovery is dependent on individual match demands.

Rugby League (RL) is a high-impact collision sport characterised by repeated sprints and numerous high-speed impacts and consequently players often report immediate and prolonged muscle soreness in the days after a match. We examined muscle soreness after matches during a full season to understand the extent to which match characteristics influence soreness. Thirty-one elite Super League players provided daily measures of muscle soreness after each of the 26 competitive fixtures of the 2012 season. Playing position, phase of the season, playing surface and match characteristics were recorded from each match. Muscle soreness peaked at day 1 and was still apparent at day 4 post-game with no attenuation in the magnitude of muscle soreness over the course of the season. Neither playing position, phase of season or playing surface had any effects on the extent of muscle soreness. Playing time and total number of collisions were significantly correlated with higher ratings of muscle soreness, especially in the forwards. These data indicate the absence "contact adaptations" in elite rugby players with soreness present throughout the entire season. Strategies must now be implemented to deal with the physical and psychological consequences of prolonged feeling of pain.

It is important to understand the extent to which physical contact changes the internal and external load during rugby simulations that aim to replicate the demands of match play. Accordingly, this study examined the role of physical contact on the physiological and perceptual demands during and immediately after a simulated rugby league match. Nineteen male rugby players completed a contact (CON) and a noncontact (NCON) version of the rugby league match-simulation protocol in a randomized crossover design with 1 wk between trials. Relative distance covered (ES = 1.27; ± 0.29), low-intensity activity (ES = 1.13; ± 0.31), high-intensity running (ES = 0.49; ± 0.34), heart rate (ES = 0.52; ± 0.35), blood lactate concentration (ES = 0.78; ± 0.34), rating of perceived exertion (RPE) (ES = 0.72; ± 0.38), and session RPE (ES = 1.45; ± 0.51) were all higher in the CON than in the NCON trial. However, peak speeds were lower in the CON trial (ES = -0.99; ± 0.40) despite unclear reductions in knee-extensor (ES = 0.19; ± 0.40) and -flexor (ES = 0.07; ± 0.43) torque. Muscle soreness was also greater after CON than in the NCON trial (ES = 0.97; ± 0.55). The addition of physical contact to the movement demands of a simulated rugby league match increases many of the external and internal demands but also results in players' slowing their peak running speed during sprints. These findings highlight the importance of including contacts in simulation protocols and training practices designed to replicate the demands of real match play.

Purpose: This study examined whether lower-volume exercise-induced muscle damage (EIMD) performed 2 weeks before high-volume muscle-damaging exercise protects against its detrimental effect on running performance., Methods: Sixteen male participants were randomly assigned to a lower-volume (five sets of ten squats, n = 8) or high-volume (ten sets of ten squats, n = 8) EIMD group and completed baseline measurements for muscle soreness, knee extensor torque, creatine kinase (CK), a 5-min fixed-intensity running bout and a 3-km running time-trial. Measurements were repeated 24 and 48 h after EIMD, and the running time-trial after 48 h. Two weeks later, both groups repeated the baseline measurements, ten sets of ten squats and the same follow-up testing (Bout 2)., Results: Data analysis revealed increases in muscle soreness and CK and decreases in knee extensor torque 24-48 h after the initial bouts of EIMD. Increases in oxygen uptake [Formula: see text], minute ventilation [Formula: see text] and rating of perceived exertion were observed during fixed-intensity running 24-48 h after EIMD Bout 1. Likewise, time increased and speed and [Formula: see text] decreased during a 3-km running time-trial 48 h after EIMD. Symptoms of EIMD, responses during fixed-intensity and running time-trial were attenuated in the days after the repeated bout of high-volume EIMD performed 2 weeks after the initial bout., Conclusions: This study demonstrates that the protective effect of lower-volume EIMD on subsequent high-volume EIMD is transferable to endurance running. Furthermore, time-trial performance was found to be preserved after a repeated bout of EIMD.

Exercise-induced muscle damage (EIMD), described as the acute weakness of the musculature after unaccustomed eccentric exercise, increases oxidative metabolism at rest and during endurance exercise. However, it is not known whether oxygen uptake during recovery from endurance exercise is increased when experiencing symptoms of EIMD. Therefore, the purpose of this study was to investigate the effects of EIMD on physiological and metabolic responses before, during and after sub-maximal running. After a 12 h fast, eight healthy male participants completed baseline measurements comprising resting metabolic rate (RMR), indirect markers of EIMD, 10 min of sub-maximal running and 30 min of recovery to ascertain excess post-exercise oxygen consumption (EPOC). Measurements were then repeated at 24 and 48 h after 100 Smith-machine squats. Data analysis revealed significant (P<0.05) increases in muscle soreness and creatine kinase (CK) and decreases in peak knee extensor torque at 24 and 48 h after squatting exercise. Moreover, RMR, physiological, metabolic and perceptual responses during sub-maximal running and EPOC were increased in the two days after squatting exercise (P<0.05). It is suggested that the elevated RMR was a consequence of a raised energy requirement for the degradation and resynthesis of damaged muscle fibres. The increased oxygen demand during sub-maximal running after muscle damage was responsible for the increase in EPOC. Individuals engaging in unaccustomed resistance exercise that results in muscle damage should be mindful of the increases in resting energy expenditure and increased metabolic demand to exercise in the days that follow.

The effects of exercise-induced muscle damage (EIMD) on the physiological, metabolic and perceptual responses during upper body arm cranking exercise are unknown. Nine physically active male participants performed 6 min of arm cranking exercise at ventilatory threshold (VT), followed by a time to exhaustion (TTE) trial at a workload corresponding to 80 % of the difference between VT and [Formula: see text] 48 h after bench pressing exercise (10 × 6 repetitions at 70 % one repetition maximum) or 20 min sitting (control). Reductions in isokinetic strength and increased muscle soreness of the elbow flexors and extensors were evident at 24 and 48 h after bench pressing exercise (P < 0.05). Despite no change in [Formula: see text], [Formula: see text], HR and blood lactate concentration ([Bla]) between conditions (P > 0.05), rating of perceived exertion (RPE) was higher during the 6 min arm cranking after bench pressing exercise compared to the control condition (P < 0.05). TTE was reduced in the treatment condition (207.2 ± 91.9 cf. 293.4 ± 75.6 s; P < 0.05), as were end [Formula: see text] (P < 0.05) and [Bla] at 0, 5 and 10 min after exercise (P < 0.05). RPE during the TTE trial was higher after bench pressing (P < 0.05), although end RPE was not different between conditions (P > 0.05). This study provides evidence that EIMD caused by bench pressing exercise increases the sense of effort during arm cranking exercise that leads to a reduced exercise tolerance. The findings have implications for individuals participating in concurrent endurance and resistance training of the upper body.

Previous research has advocated that plyometric training improves endurance performance. However, a consequence of such a training is the immediate and prolonged appearance of exercise-induced muscle damage (EIMD). This study examined whether a single bout of plyometric exercise, designed to elicit muscle damage, affected cycling endurance performance. Seventeen participants were randomly assigned to either a muscle damage (n = 7 men, 1 woman) or nonmuscle damage (n = 8 men, 1 woman) group. Before and at 48 hours, participants were measured for perceived muscle soreness, peak isokinetic strength, and physiological, metabolic, and perceptual responses during 5-minute submaximal cycling at ventilatory threshold (VT) and a 15-minute time trial. Perceived muscle soreness and isokinetic strength (p < 0.05) were significantly altered in the muscle damage group after EIMD. No changes in heart rate or blood lactate were evident during submaximal exercise (p > 0.05). However, VO2, V(E), and rating of perceived exertion (RPE) values were increased at VT in the muscle damage group at 48 hours after EIMD (p < 0.05). During the time trial, mean power output, distance covered, and VO2 were lower in the muscle damage group at 48 hours after EIMD (p < 0.05). However, there was no change in RPE (p > 0.05), suggesting effort perception was unchanged during time-trial performance after EIMD. In conclusion, individuals using concurrent plyometric and endurance training programs to improve endurance performance should be aware of the acute impact of muscle-damaging exercise on subsequent cycling performance.

Unaccustomed eccentric exercise has a profound impact on muscle structure and function. However, it is not known whether associated microvascular dysfunction disrupts the matching of O2 delivery (Qo2) to O2 utilization (Vo2). Near-infrared spectroscopy (NIRS) was used to test the hypothesis that eccentric exercise-induced muscle damage would elevate the muscle Qo2:Vo2 ratio during severe-intensity exercise while preserving the speed of the Vo2 kinetics at exercise onset. Nine physically active men completed "step" tests to severe-intensity exercise from an unloaded baseline on a cycle ergometer before (Pre) and 48 h after (Post) eccentric exercise (100 squats with a load corresponding to 70% of body mass). NIRS and breath-by-breath pulmonary Vo2 were measured continuously during the exercise tests and subsequently modeled using standard nonlinear regression techniques. There were no changes in phase II pulmonary Vo2 kinetics following the onset of exercise (time constant: Pre, 25 +/- 4 s; Post, 24 +/- 2 s; amplitude: Pre, 2.36 +/- 0.23 l/min; Post, 2.37 +/- 0.23 l/min; all P > 0.05). However, the primary (Pre, 14 +/- 3 s; Post, 19 +/- 3 s) and overall (Pre, 16 +/- 4 s; Post, 21 +/- 4 s) mean response time of the [HHb] response was significantly slower following eccentric exercise (P < 0.05). The slower [HHb] kinetics observed following eccentric exercise is consistent with an increased Qo2:Vo2 ratio during transitions to severe-intensity exercise. We propose that unchanged primary phase Vo2 kinetics are associated with an elevated Qo2:Vo2 ratio that preserves blood-myocyte O2 flux.

Exercise-induced muscle damage (EIMD) is a common occurrence following activities with a high eccentric component. Alterations to the torque-velocity relationship following EIMD would appear to have serious implications for athletic performance, particularly as they relate to impairment of maximal intensity exercise. However, this has been studied infrequently. The purpose of this study was to assess the effects of EIMD on maximal intermittent sprint performance. Ten male participants (age 22.4 +/- 3.2 years, height 178.6 +/- 5.2 cm, mass 80.6 +/- 10.7 kg) performed 10 x 6 s cycle ergometer sprints, interspersed with 24 s recovery against a load corresponding to 0.10 kp/kg and 10 x 10 m sprints from a standing start, each with 12 s active (walking) recovery. All variables were measured immediately before and at 30 min, 24, 48 and 72 h following a plyometric exercise protocol comprising of 10 x 10 maximal counter movement jumps. Repeated measures ANOVA showed significant changes over time (all P<0.05) for perceived soreness, plasma creatine kinase activity (CK), peak power output (PPO), sprint time and rate of fatigue. Soreness was significantly higher (P<0.01) than baseline values at all time intervals (3.1, 4.9, 5.5 and 3.2 at 30 min, 24, 48 and 72 h, respectively). CK was significantly elevated (P<0.05) at 24 h (239 IU/l) and 48 h (245 IU/l) compared to baseline (151 IU/l). PPO was significantly lower (P<0.05) than baseline (1,054 W) at all time intervals (888, 946, 852 and 895 W, at 30 min, 24, 48 and 72 h, respectively). The rate of fatigue over the ten cycling sprints was reduced compared to baseline, with the greatest reduction of 48% occurring at 48 h (P<0.01). This was largely attributed to the lower PPO in the initial repetitions, resulting in a lower starting point for the rate of fatigue. Values returned to normal at 72 h. Sprint times over 10 m were higher (P<0.05) at 30 min, 24 h and 48 h compared to baseline (1.96 s) with values corresponding to 2.01, 2.02 and 2.01 at 30 min, 24 h and 48 h, respectively. Values returned to baseline by 72 h. The results provide further evidence that, following a plyometric, muscle-damaging exercise protocol, the ability of the muscle to generate power is reduced for at least 3 days. This is also manifested by a small, but statistically significant reduction in very short-term (approximately 2 s) intermittent sprint running performance. These findings have implications for appropriate training strategies in multiple sprint sports.

Exercise-induced muscle damage is a well documented phenomenon particularly resulting from eccentric exercise. When eccentric exercise is unaccustomed or is performed with an increased intensity or duration, the symptoms associated with muscle damage are a common outcome and are particularly associated with participation in athletic activity. Muscle damage results in an immediate and prolonged reduction in muscle function, most notably a reduction in force-generating capacity, which has been quantified in human studies through isometric and dynamic isokinetic testing modalities. Investigations of the torque-angular velocity relationship have failed to reveal a consistent pattern of change, with inconsistent reports of functional change being dependent on the muscle action and/or angular velocity of movement. The consequences of damage on dynamic, multi-joint, sport-specific movements would appear more pertinent with regard to athletic performance, but this aspect of muscle function has been studied less often. Reductions in the ability to generate power output during single-joint movements as well as during cycling and vertical jump movements have been documented. In addition, muscle damage has been observed to increase the physiological demand of endurance exercise and to increase thermal strain during exercise in the heat. The aims of this review are to summarise the functional decrements associated with exercise-induced muscle damage, relate these decrements to theoretical views regarding underlying mechanisms (i.e. sarcomere disruption, impaired excitation-contraction coupling, preferential fibre type damage, and impaired muscle metabolism), and finally to discuss the potential impact of muscle damage on athletic performance.