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The aim of this study was to prospectively analyse the relationship between workloads and injury in elite football academy players. Elite football academy players (n = 122) from under-19 (U19) and under-21 (U21) of a professional football team competing in UEFA European Cups were followed during 5 seasons. Injuries were collected and absolute workload and workload ratios (4-weeks, 3-weeks, 2-weeks and week-to-week) calculated using a rolling days method with the help of the session Rate of Perceived Exertion. There was no association between absolute workload or workload ratio with the injury incidence in the U19. In the U21, the level of cumulative absolute workloads during 3-weeks (RR = 1.39, p = 0.026) and during 4-weeks (RR = 1.40, p = 0.019) were associated with an increase in injury. There was no association between workload ratio and injury in U21. The significant link between high cumulated 3-weeks and 4 weeks workloads and injury in U21 confirmed the requirement to monitor the internal subjective workload in U21 in order to prevent injury. Further studies exploring the relationships between workload and injury are required in football academy.

This study aimed (1) to determine the reliability of a simple and quick test to assess isometric posterior lower limb muscle force in professional football players and (2) verify its sensitivity to detect reductions in force following a competitive match. Twenty-nine professional football players performed a 3-s maximal isometric contraction of the posterior lower limb muscles for both legs with players lying supine. Both legs were tested using a knee angle of 90° and 30° measured on a force plate. Players were tested twice with one week between sessions to verify reliability. Sensitivity was tested following a full competitive football match. The test showed high reliability for dominant leg at 90° (CV = 4.3%, ICC = 0.95, ES = 0.15), non-dominant leg at 90° (CV = 5.4%, ICC = 0.95, ES = 0.14), and non-dominant leg at 30° (CV = 4.8%, ICC = 0.93, ES = 0.30) and good reliability for dominant leg at 30° (CV = 6.3%, ICC = 0.86, ES = 0.05). The measure was sensitive enough to detect reductions in force for dominant leg at 90° (P = 0.0006, ES > 1), non-dominant leg at 90° (P = 0.0142, ES = 1), and non-dominant leg at 30° (P = 0.0064, ES > 1) and for dominant leg at 30° (P = 0.0016, ES > 1). In conclusion, the present test represents a useful and practical field tool to determine the magnitude of match-induced fatigue of the posterior lower limb muscles and potentially to track their recovery.

This study aimed to compare the recovery kinetics of physical performance and subjective ratings in response to a soccer-specific exercise simulation on natural grass and artificial turf. Physical performance tests and subjective ratings were assessed on 13 professional soccer players before, immediately after, 24 h and 48 h after the test. Physical performance tests included squat jump, countermovement jump, 6-s sprint on a non-motorised treadmill and isokinetic eccentric hamstring assessment (2.09 rad · s(-1)). Hamstring peak torque decrement was higher (P < 0.05) on natural grass than on artificial turf immediately (-4.0%, CI 95%: -10.0 to 2.0%, effect size [ES] = 0.29), 24 h (-3.1%, CI 95%: -9.3 to 3.1%, ES = 0.29) and 48 h (-3.8%, CI 95%: -8.5 to 0.9%, ES = 0.43) after the test. Squat jump performance decrement was significantly lower (P < 0.05) on natural grass than artificial turf 48 h after the test (+3.7%, CI 95%: 1.1 to 6.3%, ES = 0.40). Sprint performance showed no change from baseline performance for both trials throughout the protocol. No significant interaction between surface and time was found for countermovement jump and subjective ratings. These results suggest that a one-off exercise on artificial turf does not induce greater fatigue nor does it delay the recovery process when compared to natural grass among regular artificial turf players.

In this study, we examined the effects of three recovery intensities on time spent at a high percentage of maximal oxygen uptake (t90[Vdot]O(2max)) during a short intermittent session. Eight endurance-trained male adolescents (16 +/- 1 years) performed four field tests until exhaustion: a graded test to determine maximal oxygen uptake ([Vdot]O(2max); 57.4 +/- 6.1 ml x min(-1) . kg(-1)) and maximal aerobic velocity (17.9 +/- 0.4 km x h(-1)), and three intermittent exercises consisting of repeat 30-s runs at 105% of maximal aerobic velocity alternating with 30 s active recovery at 50% (IE(50)), 67% (IE(67)), and 84% (IE(84)) of maximal aerobic velocity. In absolute values, mean t90[Vdot]O(2max) was not significantly different between IE(50) and IE(67), but both values were significantly longer compared with IE(84). When expressed in relative values (as a percentage of time to exhaustion), mean t90[Vdot]O(2max) was significantly higher during IE(67) than during IE(50). Our results show that both 50% and 67% of maximal aerobic velocity of active recovery induced extensive solicitation of the cardiorespiratory system. Our results suggest that the choice of recovery intensity depends on the exercise objective.

Using the data from Making a HIIT, this paper aimed to: 1) investigate the different heart rate (HR) quantification methods reported in school-based high-intensity interval training (HIIT) studies; and 2) assess the criterion validity of session rating of perceived exertion (RPE). During an 8-week HIIT intervention, 213 students (13.1 (0.6) years; 46% female) completed 10-minute HIIT workouts during physical education lessons. In total, 1057 HR and RPE measurements were collected across 68 HIIT workouts. For aim 1, the average and peak HR across all participants and workouts were 79% (8%) and 92% (6%) of HRmax, respectively. The average RPE was 6 (2) points on a 10-point scale. An average of 51% of students in a class had an average HR ≥ 80% for each workout. The between-person variation for peak and average HR were 19% and 30% , respectively. Both average and peak HR decreased by 0.5% each week (p < 0.001). To assess aim 2, a within-participant correlation was calculated for the internal training load produced using HR and RPE data. The correlation was 0.39 (p < 0.001), which suggests utility of using RPE when HR is not a viable option. [ABSTRACT FROM AUTHOR]

Repeated sprint ability (RSA) is more closely related to match performance outcomes than single-sprint performance, but the kinetic determinants in youth athletes remain poorly understood. Therefore, the aim of the study was to explore the kinetic determinants of RSA in youth athletes. Twenty trained adolescents (15 girls; 14.4 ± 1.0 years) completed five 15 m repetitions interspersed with 5-s rest. Velocity was measured during each trial using a radar gun at >46 Hz, following which the force–velocity–power (F-v-P) profile was fitted to a velocity–time curve and instantaneous power and force variables calculated. The mechanical efficiency of force application (DRF) was the primary predictor of both single and repeated sprint performance in adolescents. Secondly, hierarchical analyses revealed the percentage reduction in peak velocity, DRF, and allometrically scaled peak force explained 91.5% of the variance in 15 m sprint time from sprints 1–5. Finally, declines in allometrically scaled peak power were more closely related to declines in peak force than reductions in velocity. In conclusion, given DRF was the primary predictor of both single and repeated sprint performance training programmes targeting RSA need to include technique, and skill acquisition, components. [ABSTRACT FROM AUTHOR]

Alterations of aerobic fitness and muscle deoxygenation during a ramp incremental exercise test (GXT) were assessed on two occasions within a time-frame of 2.9 ± 0.1y in competitive youth cyclists. Nine cyclists (age, 14.5 ± 1.1y; peak oxygen uptake ( V ˙ O2peak), 62.6 ± 4.2 mL.min−1.kg−1) participated in this investigation. V ˙ O2peak, the gas exchange threshold (GET) and the respiratory compensation point (RCP), as well as the muscle deoxygenation response pattern were determined during a GXT using open circuit spirometry and near-infrared spectroscopy, respectively. T-tests and Pearson's correlations were used to assess effects of time on the dependent variables and relationships between changes of parameter estimates of aerobic fitness and the muscle deoxygenation response, respectively. Workrate and metabolic rate at GET (33 ± 20 and 42 ± 23%) and RCP (36 ± 20 and 40 ± 22%), and V ˙ O2peak (30 ± 18%) significantly increased throughout the study (P < 0.05). The muscle deoxygenation response showed a significant rightward shift from occasion one to two (P < 0.05). Alterations in the workrate/metabolic rate at RCP, and V ˙ O2peak, were correlated with alterations of the muscle deoxygenation response (R = 0.71–0.89, P < 0.05). Together, this is thought to indicate a superior muscle perfusion within the tissue of interrogation at the same metabolic rate on occasion two vs. one, which partially contributed to the improved aerobic fitness in the cyclists herein. [ABSTRACT FROM AUTHOR]

The purposes of this study were to determine if 1) recurrent neural networks designed for multivariate, time-series analyses outperform traditional linear and non-linear machine learning classifiers when classifying athletes based on competition level and sport played, and 2) athletes of different sports move differently during non-sport-specific movement screens. Optical-based kinematic data from 542 athletes were used as input data for nine different machine learning algorithms to classify athletes based on competition level and sport played. For the traditional machine learning classifiers, principal component analysis and feature selection were used to reduce the data dimensionality and to determine the best principal components to retain. Across tasks, recurrent neural networks and linear machine learning classifiers tended to outperform the non-linear machine learning classifiers. For all tasks, reservoir computing took the least amount of time to train. Across tasks, reservoir computing had one of the highest classification rates and took the least amount of time to train; however, interpreting the results is more difficult compared to linear classifiers. In addition, athletes were successfully classified based on sport suggesting that athletes competing in different sports move differently during non-sport specific movements. Therefore, movement assessment screens should incorporate sport-specific scoring criteria. [ABSTRACT FROM AUTHOR]

This study aimed to compare the significant turning demands of English Premier League soccer match play relative to playing position using LiDAR technology. Turning data were collected from an English Premier League soccer team (2020–2021 season; 18 fixtures) using a Sportlight® LiDAR tracking system. Turns were tracked during match play, sub-categorised by entry speed (<3.0, 3.0–5.5, 5.5–7.0 and >7.0 m/s) and turning angle (Low: 20–59°; Medium: 60–119°; High: 120–180°). Turning metric frequencies were compared between playing positions (centre backs, full-backs, central midfielders, wide midfielders, and central forwards). On average, per match, central midfielders performed more total turns (~38 vs ~18–27), turns with entry speeds <3.0 (~15 vs ~7–10) and 3.0–5.5 m/s (~21 vs ~8–15) and low (~4 vs ~1–2), medium (~10 vs ~3–6) and high angled turns (~24 vs ~12–18) compared to all other playing positions (p ≤ 0.001, d = 0.96–2.74). Approximately, 90% of turns during matches were performed with entry speeds <5.5 m/s and ~63–70% were high angled turns. This study provides unique insights into the turning demands of English Premier League soccer matches , which can be used to inform position-specific physical preparation strategies, turning testing battery selection, agility drill construction, and rehabilitation and return to play standards. [ABSTRACT FROM AUTHOR]

Substitutions are probably the most important opportunity for football coaches to actively influence a match in progress. The present article presents two studies investigating substitutions in football from two different methodological perspectives: Study I, a survey reporting the opinions of 73 licensed coaches, and Study II, data-based analysis of a total of 41,301 substitutions from 7,230 matches in seasons 2014/15 to 2018/19 of the top four European football leagues. The coaches stated to prefer offensive substitutions over defensive substitutions and additionally indicated that changing the current score was more likely to be a reason for substitution than keeping the score. The analysis of the data revealed that not offensive, but neutral substitutions, where the player is replaced by a player of the same playing position, were most frequent. However, offensive players participated significantly more frequently in substitutions. In addition, a high level of score dependence was found, as more than half of the defensive substitutions were made while winning and more than half of the offensive substitutions were made while losing. The present study sheds light on the substitution behaviour of coaches in football and intends to stimulate discussion on the optimal timing and the type of substitutions. [ABSTRACT FROM AUTHOR]

To increase physical activity levels in children, knowledge on how school playgrounds can be optimally designed is important. Until now, the contribution of playground variety and greening to children's physical activity level during recess remains unclear. This study examined the associations of school playground variety and greening with energy expenditure (EE) in elementary school children in Ecuador and Belgium. Additionally, moderating effects of study site and gender were studied. Observational data were collected using SOPLAY in ten schools in East Flanders (Belgium) and Cuenca (Ecuador). Data were analysed with linear mixed-effects model analyses. Results showed that independent of study site, EE was higher in playground areas with less green elements, and a higher level of total variety. Primary surface was only associated with EE in boys, they were more active when an artificial surface was present. Implementation of loose equipment was somewhat more strongly positively associated with EE in Ecuadorian than in Belgian children. Because of the well-known restorative effects of green elements, we do not wish to suggest that less greening should be implemented at schools. However, ideally green spaces should be designed in a way that active play is stimulated by combining green elements with other improvements. [ABSTRACT FROM AUTHOR]

Player movement metrics in football such as speed and distance are typically analysed as aggregates, sometimes outside of any specific tactical or match context. This research adds context to a player's movement over the course of a match by analysing movement profiles s and bringing together tools from the sport science and sports analytics literature. Position-specific distributions of player movement metrics: speed, acceleration and tortuosity were compared across phases of play and in-game win probability using 25 Hz optical player tracking data from all 52 matches at the 2019 FIFA Women's World Cup. Comparing the distributions using the Kolmogorov–Smirnov test and Wasserstein distances, differences were identified in these movement profiles across, in and out of possession phases, with small negligible overall positional trends across in-game win probabilities. In-game win probabilities are used in tandem with phases to present a player specific case study. The results demonstrate how sports analytics metrics can be used to contextualise a subset of movement metrics from sport science and provide a framework for analysis of further movement metrics and sports analytics modelling approaches. [ABSTRACT FROM AUTHOR]

Despite more than four decades of research examining the physical demands of match-play, quantification of the customary training loads of adult male professional soccer players is comparatively recent. The training loads experienced by players during weekly micro-cycles are influenced by phase of season, player position, frequency of games, player starting status, player-specific training goals and club coaching philosophy. From a macronutrient perspective, the periodization of physical loading within (i.e., match versus training days) and between contrasting micro-cycles (e.g., 1, 2 or 3 games per week schedules) has implications for daily carbohydrate (CHO) requirements. Indeed, aside from the well-recognised role of muscle glycogen as the predominant energy source during match-play, it is now recognised that the glycogen granule may exert regulatory roles in activating or attenuating the molecular machinery that modulate skeletal muscle adaptations to training. With this in mind, the concept of CHO periodization is gaining in popularity, whereby CHO intake is adjusted day-by-day and meal-by-meal according to the fuelling demands and specific goals of the upcoming session. On this basis, the present paper provides a contemporary overview and theoretical framework for which to periodize CHO availability for the professional soccer player according to the "fuel for the work" paradigm. [ABSTRACT FROM AUTHOR]

The associations between swimming and cycling abilities and fitness levels in 9–11-year-old children were examined. A cross-sectional study involving 2258 children (50.7% boys; aged 10.52 ± 0.6 years) from 33 schools across Wales, participated in Swan/BridgeLinx health, fitness, and lifestyle programmes between 2013–2019. Health and fitness data were collected; namely body composition, cardiorespiratory fitness, muscular strength, flexibility, power, and speed using standardised measures. Children completed an online survey collecting data on swimming and cycling abilities and sports club attendance. Multivariate multilevel regressions were used to examine the associations between measures. The ability to swim and cycle was significantly (p < 0.05) associated with all components of fitness when accounting for age, body mass index (BMI), deprivation, gender, and sports club attendance. Boys outperformed girls with significant interactions between swimming, cycling and cardiorespiratory fitness for gender by swim (p = 0.001) and gender by cycle (p = 0.015). The gender by cycle interaction significantly predicted grip strength and power (p < 0.05). Swimming and cycling are important "milestones" in the journey of motor development and are associated with higher levels of fitness. These activities should be promoted to allow for an optimal development of motor skills, fitness, and health. [ABSTRACT FROM AUTHOR]

High-speed running (HSR) loads have been linked with non-contact injury risks in team-sports. This study investigated whether player-specific speed zones, reflecting individual fitness characteristics, impact the associations between non-contact injury and acute and chronic HSR loads. Semi-professional soccer players from two clubs (n = 47) were tracked over two seasons using 10 Hz GPS (5552 observations). HSR distances were calculated arbitrarily (≥5.5 m·s−1), and in an individualised fashion based on the final speed of the 30–15 intermittent fitness test. Cumulative running loads were represented by exponentially weighted moving averages with 7-(acute) and 28-day (chronic) decay parameters. Physiotherapists collected non-contact, lower-limb, time-loss injury data (n = 101). Injury models using session type (training vs matches), coach, as well as arbitrary or individualised running loads were constructed via mixed-effect logistic regression. Session type had the largest effect on injury (training vs match OR = 0.28; 95%CI:0.17–0.44). Variations in individualised or arbitrary acute and chronic HSR loads within the mid-range of the observed data had negligible effects on predicted injury risk. However, the uncertainty of estimated effects at extreme values of acute and chronic HSR loads prevented any conclusive findings. Therefore, the efficacy of using customised speed thresholds in quantifying load for injury risk mitigation purposes remains unclear. [ABSTRACT FROM AUTHOR]

We assessed the association between school time and physical fitness in adolescents. The study included 2,024 adolescents, aged 12.5–17.5 years, who participated in the Healthy Lifestyle in Europe by Nutrition in Adolescence study. Health-related physical fitness components were assessed using the physical fitness tests battery. Cardiovascular risk was categorized using the sex-specific cut-offs for a healthy cardiorespiratory fitness level in adolescents proposed by FitnessGram®. School time was classified as short or long. Multivariate analysis accounted for confounding factors such age, sex, body mass index, time spent in moderate to vigorous physical activity, pubertal status, and parents' educational level. Cardiorespiratory fitness was higher in adolescents with a long school time than in those with a short school time (42.0 ± 7.6 vs 40.7 ± 7.2 mL.kg–1.min–1, respectively; p < 0.05). The percentage of adolescents at cardiovascular risk in adulthood was higher in the short than in the long time group (45.2% vs 31.7%, respectively) (p < 0.05). These findings suggest that a long school day is associated with higher cardiorespiratory fitness in adolescents and that school time should be considered in interventions and health promotion strategies. [ABSTRACT FROM AUTHOR]

The International Paralympic Committee (IPC) mandates Paralympic Sports to develop evidence-based classification systems that allocate athletes into 'classes' according to the impact of their impairment on sport-specific performance. In wheelchair-basketball, a panel of classifiers assesses athlete's performance through observation. One key barrier to evidence-based classification is the absence of defined eligible impairments, including clear guidelines on how to assess them and their impact on wheelchair basketball performance. This study aims to reach expert consensus on issues specific to wheelchair basketball that can benefit from evidence-based classification. It offers recommendations for refining the classification manual, thus improving adherence to the IPC classification code. A three-round Delphi study was conducted with 29 experts in wheelchair basketball. The experts agreed with the new definition for the aim of wheelchair basketball classification, which is in line with the IPC code. Cases identified as having the highest risk for disagreement between classifiers included classifying players with upper limb deficiency or with impaired coordination. The panel failed to agree on changing the classification procedures and on defining the eligible impairment list. This study identifies issues specific to wheelchair basketball classification to be addressed in future research. Additional discussions need to take place to promote further resolution. [ABSTRACT FROM AUTHOR]

The purpose of this study was to analyze the influence of grade of obesity on the probability of achieving a VO2 plateau and threshold secondary criteria for verifying VO2max during a treadmill walk test in youths with obesity. Therefore, 72 youths with obesity (aged 8-16) performed an incremental treadmill walk test to exhaustion during which oxygen uptake (VO2), minute ventilation (VE), heart rate (HR) and rating of perceived exertion were continuously measured. HR corresponding to a "hard" level of perceived exertion was reported and expressed as a percentage of the predicted HRmax. The rate of achievement of criteria for validation VO2max (VO2 plateau; HR>95% theoretical HRmax; RER>1.0; rating of perceived exertion ≥ "hard") was compared between participants with grade I and grade II obesity. 37% of the participants achieved a VO2 plateau and 23% achieved both an HR>95% and RER >1.0. Youths with grade II obesity had lower minute ventilation (p<0.01) tended to be more likely to reach an HR>95% (OR = 0.33; P=0.06) and a "hard" rating of perceived exertion than grade I (OR = 4.5; P=0.07). However, there was no influence of grade of obesity on the achievement of VO2 plateau, and RER>1.0. [ABSTRACT FROM AUTHOR]

The aims in the present study were to assess reliability for two unilateral and two bilateral field-based hamstring assessments and compare magnitude, direction and agreement of inter-limb asymmetry between tests and sessions. Twenty-nine female soccer players (age: 21.1 ± 4.5 years; height: 169.7 ± 5.8 cm; body mass: 66.2 ± 6.4 kg) performed three repetitions per leg of unilateral isometric 30° and 90° knee flexion (KF) tasks, and three repetitions total for a bilateral 90° isometric KF and Nordic hamstring exercise. Absolute reliability of most methods were acceptable (<10%). Relative reliability within-session was fair to excellent (ICC≥0.784; lower bound 95%CI ≥0.623). Greater variability in between-session relative reliability was observed during the unilateral tests, demonstrating poor to good (ICC = 0.698–0.798; lower bound 95%CI = 0.274–0.638). Bilateral assessments demonstrated similar ranges of poor to excellent (ICC = 0.679–0.963; lower bound 95%CI = 0.231–0.790). Agreement between-session for inter-limb asymmetry identification was slight and fair in the unilateral tests, with moderate to substantial agreement demonstrated in the bilateral. Being the most reliable within- and between-sessions, demonstrating substantial agreement in asymmetry between-sessions, the NHE would be most appropriate to identify inter-limb asymmetry and assess chronic changes in hamstring strength. [ABSTRACT FROM AUTHOR]

The study examined the utility of surrogate measures of athletic performance to determine locomotor qualities (maximal aerobic velocity and peak velocity) in elite Australian Football (AF). 29 professional AF players undertook aerobic fitness (3km time-trial [TT] and 30–15 Intermittent Fitness Test [30–15 IFT]) and peak velocity (PV; 50 m maximal sprints using 10Hz GPS) assessments in pre-season. Characteristics of TT performance (mean velocity, 500m and 1km splits) were compared with a surrogate for maximal aerobic velocity (MAV; 80% of 30–15 IFT final velocity). PVs derived from sprint tests were compared to those attained in AF matches (10 Hz GPS). Higher Pearson correlations were observed between MAV versus the fastest 500m (r = 0.74) and 1km (r = 0.75) of the 3km TT, but they were not superior to mean velocity (r = 0.72; p ≥ 0.30) which also demonstrated the lowest bias (p ≤ 0.01) and equivalent typical errors (0.16–0.17 m.s−1). Peak velocity was higher across match observations (0.28, CI: ± 0.17 m.s −1, p = 0.017) versus sprint tests. There was no impact of playing position on the determination of locomotor qualities using surrogate measures of locomotor qualities. Locomotor qualities can be determined practically using 10Hz GPS devices during 3km time-trials and competitive matches (assuming appropriate signal quality), without additional fitness assessments. [ABSTRACT FROM AUTHOR]

Football boots are marketed with emphasis on a single key performance characteristic (e.g. speed). Little is known on how design parameters impact players' performance. This study investigated the impact of boot design on performance maintenance and perceived foot comfort during a 90-minute match simulation drill. Eleven male university football players tested two commercially available "sprint boots" known to generate significantly different plantar pressures (high=Boot H and low=Boot L). Players completed a modified Soccer-specific Aerobic Field Test on a 3G pitch. Heart rate, rated perceived exertion and perceived foot discomfort were assessed for each 15-min interval. Power generation was assessed pre- and post-match simulation. A significantly higher mean heart rate was seen for Boot L in the 60th–75th and 75th–90th minute intervals (P = 0.017, P = 0.012 respectively). Perceived exertion did not differ between boots (P ≥ 0.302). Power generation significantly decreased in Boot H between pre- and post-match (P = 0.042). Both boots increased discomfort with significantly more plantar discomfort felt in the last 30 min in Boot H (75th min: P = 0.037; 90th min: P = 0.048). The results imply that a comfortable boot design may improve maintenance of performance during match-play. [ABSTRACT FROM AUTHOR]

To establish the test–retest reliability of pulmonary oxygen uptake (V̇O2), muscle deoxygenation (deoxy[haem]) and tissue oxygen saturation (StO2) kinetics in youth elite-cyclists. From baseline pedalling, 15 youth cyclists completed 6-min step transitions to a moderate- and heavy-intensity work rate separated by 8 min of baseline cycling. The protocol was repeated after 1 h of passive rest. V̇O2 was measured breath-by-breath alongside deoxy[haem] and StO2 of the vastus lateralis by near-infrared spectroscopy. Reliability was assessed using 95% limits of agreement (LoA), the typical error (TE) and the intraclass correlation coefficient (ICC). During moderate- and heavy-intensity step cycling, TEs for the amplitude, time delay and time constant ranged between 3.5–21.9% and 3.9–12.1% for V̇O2 and between 6.6–13.7% and 3.5–10.4% for deoxy[haem], respectively. The 95% confidence interval for estimating the kinetic parameters significantly improved for ensemble-averaged transitions of V̇O2 (p < 0.01) but not for deoxy[haem]. For StO2, the TEs for the baseline, end-exercise and the rate of deoxygenation were 1.0–42.5% and 1.1–5.5% during moderate- and heavy-intensity exercise, respectively. The ICC ranged from 0.81 to 0.99 for all measures. Test–retest reliability data provide limits within which changes in V̇O2, deoxy[haem] and StO2 kinetics may be interpreted with confidence in youth athletes. [ABSTRACT FROM AUTHOR]

This investigation examined the effect of prior workload on high-intensity football match performance. Player load variables were recorded using a global positioning system and converted into composite variables: rolling season accumulated load (AL), exponentially weighted moving average acute, chronic and acute:chronic workload ratio (A:C). Match-play high-intensity performance-per-minute: accelerations (ACC), sprints, high-speed running (HSR) and high metabolic load (HMLd) distances; and situational and contextual variables were recorded for all games. Partial least squares modelling, and backward stepwise selection determined the most parsimonious model for each performance variable. Quadratic relationships of small to moderate effect sizes were identified for sprint AL and sprint performance, HSR AL and HSR performance, acute HMLd and HMLd performance, acute sprint load and ACC performance and A:C sprint load and ACC performance. Match performance was typically greatest between the mean and +1SD. High chronic HMLd, and combined acceleration and deceleration (ACC+DEC) load exerted small beneficial effects on HMLd and HSR performance, whereas high acute load exerted trivial to moderate negative effects. High sprint A:C exerted a small beneficial effect on sprint performance and playing position exerted small effects on HSR and HMLd performance. Prior workload has trivial to moderate effects on high-intensity match performance in professional players. [ABSTRACT FROM AUTHOR]

The effects of acute ingestion of nitrate on short-duration repeated sprint performance (RSP) are unclear. This study investigated the effect of acute ingestion of beetroot juice on a test of RSP in team sport athletes. Sixteen male team sport athletes undertook four trials using a 40 m maximum shuttle run test (MST), which incorporates 10 × 40 m shuttle sprints with 30 s between the start of each sprint. Two familiarisation trials, followed by nitrate-rich beetroot juice (BR; ~6 mmol nitrate) and nitrate-depleted beetroot juice (PLA; ~0.0034 mmol nitrate) trials were completed in a randomised, double-blind manner. Ingestion of beetroot juice 3 h prior to exercise elevated plasma nitrate concentrations ~6-fold in BR (BR, 413 ± 56 μM; PLA, 69 ± 30 μM; P < 0.001). RSP, assessed by sprint performance decrement (Sdec; %), did not differ (P = 0.337) between BR (5.31 ± 2.49%) and PLA (5.71 ± 2.61%). There was no difference between trials for total sprint time (P = 0.806), fastest sprint (P = 0.341), slowest sprint (P = 0.787), or post-exercise blood lactate concentration (BR, 11.8 ± 2.5 mM; PLA, 12.2 ± 2.3 mM; P = 0.109). Therefore, acute ingestion of beetroot juice did not improve a test of short-duration RSP in team sport athletes. [ABSTRACT FROM AUTHOR]

With potential implications for recovery and conditioning practices, the aim of this study was to assess the cumulative and residual response of angle specific eccentric knee flexor (eccKF) strength indices following soccer-specific activity. Thirteen semi-professional soccer players were therefore required to complete a 90-minute soccer-specific treadmill running. with eccKF isokinetic strength assessments completed pre-trial, immediately post-trial, and 48 hours post-trial. The strength assessments comprised the completion of 5 repetitions at angular velocities of 60 and 300 deg·s−1. Isokinetic data was analysed for measures of peak torque (PT), angle of peak torque (APT), functional range (FR), and angle specific torque (AST). Significant post-trial impairments were observed for measures of slow velocity PT60 (6.6%) and AST300 (12.5%). Further significant differences were observed 48 hours post-trial for PT300 (10.7%) and PT60 (12.8%) PT, APT60 (~15°), and AST300 (>13.6%). These data have implications for post exercise recovery monitoring and the prescription of recovery modalities and conditioning practices in the 2 days following match-play. The AST and APT responses highlight the importance of analysis of the entire strength-angle curve and at a range of angular velocities. [ABSTRACT FROM AUTHOR]

We examine how mental fatigue (MF) influences peripheral perception, tactical behaviour, and physical performance of soccer players during a standardized small-sided game. Eighteen male university first-team soccer players participated. A modified Stroop task and the Vienna Test System were employed to induce MF and to evaluate players' peripheral perception, respectively. The FUT-SAT test was used to assess participants' tactical behaviour and physical performance was quantified using GPS technology. MF decreased players' visual field (pre-test = 189.9° and post-test = 181.6°). Additionally, MF constrained players to more frequently perform actions related to the tactical principles of penetration, depth mobility, and defensive unity, and less frequently perform actions of defensive coverage and balance. During MF, players showed decreased accuracy in actions related to the principles of offensive coverage, width and length, offensive unity, delay, balance, concentration, and defensive unity. Finally, under MF players covered higher total distance and at more moderate speed. MF decreased players' peripheral perception, making them prioritize actions towards the opposing goal and protecting their own goal, while displaying more errors for most tactical actions. In summary, MF impaired several aspects of players' cognitive and tactical behaviours, causing a compensatory increase in physical performance. [ABSTRACT FROM AUTHOR]

Research has demonstrated that induced mental fatigue impairs soccer-specific technical, tactical and physical performance in soccer players. The findings are limited by the lack of elite players and low ecological validity of the tasks used to induce mental fatigue, which do not resemble the cognitive demands of soccer. The current study collected survey data from English academy soccer players (n = 256; age groups - U14 – U23), with questions comprising of five themes (descriptors of physical and mental fatigue, travel, education, match-play and fixture congestion). The survey consisted of multiple choice responses, checkboxes and blinded/unblinded (for duration based questions) 0-100 arbitrary unit (AU) slider scales. Listening to music (81.6% of players), using social media (58.3%) and watching videos (34.3%) were the most common pre-match activities. Pre-match subjective mental fatigue was low (18.7±18.8 AU), and most frequently reported at the end of a match (47±26 AU) and remained elevated 24-hours post-match (36±27 AU). Travel (29±24 AU), fixture congestion (44±25 AU) and education (30±26 AU) demonstrated a low to moderate presence of subjective mental fatigue. These findings provide an overview of activities performed by English academy soccer players pre-match, and demonstrate that mental fatigue is experienced as a result of match-play. [ABSTRACT FROM AUTHOR]

The current study compared cold-water immersion (CWI) and active recovery (AR) to static stretching (SS) on muscle recovery post-competitive soccer matches in elite youth players (n = 15). In a controlled crossover design, participants played a total of nine competitive soccer games, comprising three 80 minute games for each intervention (SS, CWI and AR). Muscle oedema, creatine kinase (CK), countermovement jump performance (CMJA) and perceived muscle soreness (PMS) were assessed pre-, immediately post-, and 48 hours post-match and compared across time-intervals and between interventions. Following SS, all markers of muscle damage remained significantly elevated (P < 0.05) compared to baseline at 48 hours post-match. Following AR and CWI, CMJA returned to baseline at 48 hours post-match, whilst CK returned to baseline following CWI at 48 hours post-match only. Analysis between recovery interventions revealed a significant improvement in PMS (P < 0.05) at 48 hours post-match when comparing AR and CWI to SS, with no significant differences between AR and CWI observed (P > 0.05). Analysis of %change for CK and CMJA revealed significant improvements for AR and CWI compared to SS. The present study indicated both AR and CWI are beneficial recovery interventions for elite young soccer players following competitive soccer matches, of which were superior to SS. [ABSTRACT FROM AUTHOR]

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = −0.26 to 0.18) and CMJ and DJ (Kappa = −0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists. [ABSTRACT FROM AUTHOR]

This study validated sedentary behaviour (SB), moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) accelerometer cut-points in 5–7-year-old children. Participants (n = 49, 55% girls) wore an ActiGraph GT9X accelerometer, recording data at 100 Hz downloaded in 1 s epochs, on both wrists and the right hip during a standardised protocol and recess. Cut-points were generated using ROC analysis with direct observation as a criterion. Subsequently, cut-points were optimised using Confidence intervals equivalency analysis and then cross-validated in a cross-validation group. SB cut-points were 36 mg (Sensitivity (Sn) = 79.8%, Specificity (Sp) = 56.8%) for non-dominant wrist, 39 mg (Sn = 75.4%, Sp = 70.2%) for dominant wrist and 20 mg (Sn = 78%, Sp = 50.1%) for hip. MVPA cut-points were 189 mg (Sn = 82.6%, Sp = 78%) for non-dominant wrist, 181 mg (Sn = 79.1%, Sp = 76%) for dominant wrist and 95 mg (Sn = 79.3%, Sp = 75.6%) for hip. VPA cut-points were 536 mg (Sn = 75.1%, Sp = 68.7%) for non-dominant wrist, 534 mg (Sn = 67.6%, Sp = 95.6%) for dominant wrist and 325 mg (Sn = 78.2%, Sp = 96.1%) for hip. All placements demonstrated adequate levels of accuracy for SB and PA assessment. [ABSTRACT FROM AUTHOR]

This study aimed to assess the effect of playing surface (Natural [NT] and Artificial [AT] Turf) on the fatigue response to a soccer-specific exercise protocol (SSEP). Eighteen male soccer players completed the SSEP on NT and AT with pre-, post-, and 48 h post-assessments of eccentric knee flexor (eccKF) and concentric knee extensor peak torque (PT), peak countermovement (CMJ) and squat jump (SJ) height, and Nordic hamstring break angle. No significant main effects for surface or any surface and time interactions were observed for any of the outcome measures, except for eccKF PT recorded at 3.14 rad·s-1, which was significantly lower 48 h post-trial in the AT condition (AT = 146.3 ± 20.4 Nm; NT = 158.8 ± 24.7 Nm). Main effects for time were observed between pre- and post-trial measures for eccKF PT at all angular velocities, Nordic break angle, CMJ and SJ height. Nordic break angle, and both CMJ and SJ height were significantly impaired 48 h post-trial when compared to pre-trial. The findings of the current study suggest surface dependent changes in eccKF PT which may have implications for recovery and subsequent performance after competition on AT. [ABSTRACT FROM AUTHOR]

High-intensity-interval-training (HIIT) has been suggested to have beneficial effects in multiple populations across individual systematic reviews, although there is a lack of clarity in the totality of the evidence whether HIIT is effective and safe across different populations and outcomes. The aim of this meta-review was to establish the benefits, safety and adherence of HIIT interventions across all populations from systematic reviews and meta-analyses. Major databases were searched for systematic reviews (with/without meta-analyses) of randomised & non-randomised trials that compared HIIT to a control. Thirty-three systematic reviews (including 25 meta-analyses) were retrieved encompassing healthy subjects and people with physical health complications. Evidence suggested HIIT improved cardiorespiratory fitness, anthropometric measures, blood glucose and glycaemic control, arterial compliance and vascular function, cardiac function, heart rate, some inflammatory markers, exercise capacity and muscle mass, versus non-active controls. Compared to active controls, HIIT improved cardiorespiratory fitness, some inflammatory markers and muscle structure. Improvements in anxiety and depression were seen compared to pre-training. Additionally, no acute injuries were reported, and mean adherence rates surpassed 80% in most systematic reviews. Thus, HIIT is associated with multiple benefits. Further large-scale high-quality studies are needed to reaffirm and expand these findings. Abbreviations: ACSM: American College of Sports Medicine; BMI: Body Mass Index; BNP: Brain Natriuretic Peptide; BP: Blood Pressure; CAD: Coronary Artery Disease; CHD: Coronary Heart Disease; COPD: Chronic Obstructive Pulmonary Disease; CRP: c- reactive Protein; CVD: Cardiovascular Disease; DBP: Diastolic Blood Pressure; ES: Effect Size; FAS: Reduced Fatty Acid Synthase; FATP-1: Reduced Fatty Acid Transport Protein 1; FMD: Flow Mediated Dilation; Hs-CRP: High-sensitivity c- reactive Protein; HDL: High Density Lipoprotein; HIIT: High-Intensity Interval Training; HOMA: Homoeostatic Model Assessment; HR: Heart Rate; HTx: Heart Transplant Recipients; IL-6: Interleukin-6; LDL: Low Density Lipoprotein; LV: Left Ventricular; LVEF: Left Ventricular Ejection Fraction; MD: Mean Difference; MetS: Metabolic Syndrome; MPO: Myeloperoxidase; MICT: Moderate-Intensity Continuous Training; NO: Nitric Oxide; NRCT: Non-Randomised Controlled Trial; PA: Physical Activity; PAI-1: Plasminogen-activator-inhibitor-1; QoL: Quality of Life; RCT: Randomised Controlled Trial; RoB: Risk of Bias; RPP: Rate Pressure Product; RT: Resistance Training; SBP: Systolic Blood Pressure; SD: Standardised Difference; SMD: Standardised Mean Difference; TAU: Treatment-As-Usual; T2DM: Type 2 Diabetes Mellitus; TC: Total Cholesterol; TG: Triglycerides; TNF-alfa: Tumour Necrosis Factor alpha; UMD: Unstandardised Mean Difference; WC: Waist Circumference; WHR: Waist-to-Hip Ratio; WMD: Weighted Mean Difference Key points: HIIT may improve cardiorespiratory fitness, cardiovascular function, anthropometric variables, exercise capacity, muscular structure and function, and anxiety and depression severity in healthy individuals and those with physical health disorders. Additionally, HIIT appears to be safe and does not seem to be associated with acute injuries or serious cardiovascular events. [ABSTRACT FROM AUTHOR]

This study assessed the intra-individual reliability of oxygen saturation in intercostal muscles (SmO2-m.intercostales) during an incremental maximal treadmill exercise by using portable NIRS devices in a test-retest study. Fifteen marathon runners (age, 24.9 ± 2.0 years; body mass index, 21.6 ± 2.3 kg·m−2; V̇O2-peak, 63.7 ± 5.9 mL·kg−1·min−1) were tested on two separate days, with a 7-day interval between the two measurements. Oxygen consumption (V̇O2) was assessed using the breath-by-breath method during the V̇O2-test, while SmO2 was determined using a portable commercial device, based in the near-infrared spectroscopy (NIRS) principle. The minute ventilation (VE), respiratory rate (RR), and tidal volume (Vt) were also monitored during the cardiopulmonary exercise test. For the SmO2-m.intercostales, the intraclass correlation coefficient (ICC) at rest, first (VT1) and second ventilatory (VT2) thresholds, and maximal stages were 0.90, 0.84, 0.92, and 0.93, respectively; the confidence intervals ranged from −10.8% – +9.5% to −15.3% – +12.5%. The reliability was good at low intensity (rest and VT1) and excellent at high intensity (VT2 and max). The Spearman correlation test revealed (p ≤ 0.001) an inverse association of SmO2-m.intercostales with V̇O2 (ρ = −0.64), VE (ρ = −0.73), RR (ρ = −0.70), and Vt (ρ = −0.63). The relationship with the ventilatory variables showed that increased breathing effort during exercise could be registered adequately using a NIRS portable device. [ABSTRACT FROM AUTHOR]

Introduction: High-Intensity Interval Training (HIIT) and Constant-Intensity Endurance Training (CIET) improves peak oxygen uptake (V̇O2) similarly in adults; but in children this remains unclear, as does the influence of maturity. Methods: Thirty-seven boys formed three groups: HIIT (football; n = 14; 14.3 ± 3.1 years), CIET (distance runners; n = 12; 13.1 ± 2.5 years) and a control (CON) group (n = 11; 13.7 ± 3.2 years). Peak V̇O2 and gas exchange threshold (GET) were determined from a ramp test and anaerobic performance using a 30 m sprint pre-and-post a three-month training cycle. Results: The HIIT groups peak V̇O2 was significantly higher than the CON group pre (peak V̇O2: 2.54 ± 0.63 l·min-1 vs 2.03 ± 0.53 l·min-1, d = 0.88; GET: 1.41 ± 0.26 l·min-1 vs 1.13 ± 0.29 l·min-1, d = 1.02) and post-training (peak V̇O2: 2.63 ± 0.73 l·min-1 vs 2.08 ± 0.64 l·min-1, d = 0.80; GET: 1.32 ± 0.33 l·min-1 vs 1.15 ± 0.38 l·min-1, d = 0.48). All groups showed a similar magnitude of change during the training (p > 0.05). Conclusion: HIIT was not superior to CIET for improving aerobic or anaerobic parameters in adolescents. Secondly, pre- and post-pubertal participants demonstrated similar trainability. [ABSTRACT FROM AUTHOR]

Little is known regarding the influence of asthma and exercise, and their interaction, on heart rate variability (HRV) in adolescents. Thirty-one adolescents with asthma (13.7±0.9 years; 21.9±3.9 kg·m−2; 19 boys, 12 girls) and thirty-three healthy adolescents (13.8±0.9 years; 20.3±3.2 kg·m−2; 16 boys, 17 girls) completed an incremental ramp test and three heavy-intensity constant-work-rate cycle tests. Thirteen adolescents (7 boys, 6 girls; 6 asthma, 7 control) completed six-months high-intensity interval training (HIIT) and were compared to age- and sex-matched controls. Standard time-domain, frequency-domain and non-linear indices of HRV were derived at baseline, three- and six-months. Asthma did not influence HRV at baseline or following HIIT. Total power, low frequency and normalised low frequency power, and sympathovagal balance increased at three-months in HIIT, subsequently declining towards baseline at six-months. Normalised high frequency power was reduced at three-months in both groups, which was sustained at six-months. No effects of HIIT were observed in the time-domain nor in the non-linear indices. HRV was not influenced by asthma, potentially because such derangements are a function of disease progression, severity or duration. HIIT may be associated with a short-term shift towards greater sympathetic predominance during exercise, perhaps caused by physiological overload and fatigue. [ABSTRACT FROM AUTHOR]

Improving sedentary measurement is critical to understanding sedentary-health associations in youth. This study assessed agreement between the thigh-worn activPAL and commonly used hip-worn ActiGraph accelerometer methods for assessing sedentary patterns in children. Both devices were worn by 8–12-year-olds (N = 195) for 4.6 ± 1.9 days. Two ActiGraph cut-points were applied to two epoch durations: ≤25 counts (c)/15 s, ≤75c/15s, ≤100c/60s, and ≤300c/60s. Bias, mean absolute deviation (MAD), and intraclass correlation coefficients (ICCs) tested agreement between devices for total sedentary time and 11 sedentary pattern variables (usual bout duration, sedentary time accumulated in various bout durations, breaks/day, break rate, and alpha). For most sedentary pattern variables, ActiGraph 25c/15s, 75c/15s, and 100c/60s had poor ICCs, with bias and MAD >20%. ActiGraph 300c/60s had a better agreement than the other cut-points, but all ICCs were <0.587. ActiGraph underestimated sedentary time in longer bouts and usual bout duration, and overestimated sedentary time in shorter bouts, breaks/day, and alpha. For total sedentary time, ActiGraph 25c/15s, 300c/60s, and 75c/15s had good/fair ICCs, with bias and MAD <20%. Sedentary patterns derived from two commonly used ActiGraph cut-points did not appear to reflect postural changes. These differences between measurement devices should be considered when interpreting findings from sedentary pattern studies. [ABSTRACT FROM AUTHOR]

Aim was to identify critical load (CL) in young and elderly apparently healthy male cohorts. To contrast the metabolic, cardiovascular and perceptual responses on CL according to age. We evaluated 12 young (23 ± 3 years) and 10 elderly (70 ± 2 years) apparently healthy active males, who underwent: (1) 1 repetition maximum (1RM) test on a 45° Leg Press; (2) on different days, three high-intensity resistance exercise constant load tests (60%, 75% and 90% 1RM) until fatigue (Tlim). Absolute values of both the CL asymptote and curvature constant (kg) were significantly lower in elderly subjects (P < 0.05). In contrast, elderly subjects demonstrated a significantly higher number of repetitions at CL when compared with young subjects (P < 0.05). As expected, oxygen uptake (VO2) and heart rate (HR) during maximal aerobic exercise testing were significantly reduced in older subjects. However, percent-predicted aerobic capacity were higher in older subjects (P < 0.05). In addition, blood lactate ([La−]) corrected to Tlim and rating of perceived exertion values were greater in younger subjects at all intensities (P < 0.05). These findings, despite reduced force production in older subjects, endurance-related parameters are well preserved according to age-adjusted percent-predicted values in apparently healthy males. [ABSTRACT FROM AUTHOR]

We aimed to evaluate the internal consistency and factor structure of the Functional Movement Screen (FMSTM) in youth athletes and quantify differences between individual task score at different stages of maturation. FMSTM and anthropometric variables were measured in 144 youth athletes (96 female, 48 male). Biological maturation was categorised as before- (<-0.5 years), at- (−0.49–0.50 years) and after- peak height velocity [PHV] (>0.51 years). Internal consistency was poor (Cronbach's alpha; 0.53, ±90% confidence limit 0.10; ordinal alpha 0.6, ±0.09). Principle component analysis extracted two components, representing 47% of the total variance. Tasks loading highest on component 1 required stability, while those loading highest on component 2 favoured mobility. "Likely" decrements in component 1 tasks were observed before-PHV. In-line lunge (effect size ±90% confidence limit; −0.47, ±0.49), hurdle step (−0.38, ±0.49), and trunk stability push-up (−0.51, ±0.45), were lower compared with athletes at-PHV and rotatory stability (−0.44, ±0.37) was lower than those after-PHV. Boys' scored "most likely", higher (0.73, ±0.28) in trunk stability push-up, and girls "likely" higher in shoulder mobility (0.46, ±0.29). In our population, the FMSTM is not uni-dimensional, thus total score should be avoided. Clear maturation affects were observed in stability tasks. [ABSTRACT FROM AUTHOR]

The aim of the current study was to investigate positional specific physical performance and external load responses to short term fixture congestion in English professional soccer. A total of 515 match observations were categorised as G1: the first game in a week with >4 days following a previous game, G2: the second game in a week played <4 days since G1, and G3: the third game in a week played with <4 days between each of the previous games. Global positioning system and accelerometer-based metrics were partitioned into fifteen-minute epochs. These data were then analysed using a linear mixed model to assess both the within and between game positional differences. Total, low-intensity (<4.0 m·s−1), medium-intensity (MID; 4.0–5.5 m·s−1), and sprint distance (>7.0 m·s−1) were significantly different across games. No between game positional differences were identified; however, within match position specific differences were observed for measures of MID and HID. No significant differences were evident for accelerometer derived metrics between games or across positions. The current data suggests that the use of fifteen minute within game epochs enables the detection of alterations in physical output during congested schedules. The observed within game positional differences has implications for player specific conditioning and squad rotation strategies. [ABSTRACT FROM AUTHOR]

Small-sided games (SSG) are played on a small pitch, often using modified rules and involving a smaller number of players. This article aimed to critically analyse the literature to determine how small-sided games affect the performance of football players in the short- and long term. Electronic databases were searched for literature dating from January 2000 to July 2018. The methodological quality of the studies was evaluated using the modified Downs and Black Quality Index (cross-sectional studies) and the Physiotherapy Evidence Database (PEDro) scale (intervention studies). Fifty-three studies, 44 cross-sectional and 9 intervention studies, met the inclusionary criteria for review. Most of the cross-sectional studies focused on describing the differences between SSG protocols, whereas 4 studies focused on making a comparison between "interval" and "continuous" SSG training regimes. On the other hand, intervention studies focused on making a comparison between SSG-based protocols and high-intensity intermittent training (HIIT)-based running protocols, in addition to determine the effect of a SSG-based training programme alone. SSG-based football plans (2 to 4 SSG sessions per week) show athletic performance improvements in football players by improving sprint, repeated sprint ability (RSA) and change of direction (COD) along with muscular and physiological adaptation. [ABSTRACT FROM AUTHOR]

This randomised controlled trial investigated changes in eccentric hamstring strength, 10m sprint speed, and change-of-direction (COD) performance immediately post Nordic hamstring curl (NHC) intervention and following a 3-week detraining period. Fourteen male team sports athletes were randomised to a do-as-usual control group (CG; n = 7) or to a NHC intervention group (NHC; n = 7). Isokinetic dynamometry at 180°/s evaluated eccentric hamstring strength immediately post-intervention as the primary outcome measure. Secondary outcomes included 10 m sprint time and COD. Each outcome was measured, pre, immediately post-intervention and following a 3-week detraining period. Immediately post-intervention significant group differences were observed in the NHC group for eccentric hamstring strength (31.81 Nm−1 vs. 6.44 Nm−1, P = 0.001), COD (−0.12 s vs. 0.20 s; P = 0.003) and sprint (- 0.06 s vs. 0.05 s; P = 0.024) performance. Performance improvements were maintained following a detraining period for COD (−0.11 s vs. 0.20 s; P = 0.014) and sprint (−0.05 s vs. 0.03 s, P = 0.031) but not eccentric hamstring strength (15.67 Nm−1 vs. 6.44 Nm−1, P = 0.145) These findings have important implications for training programmes designed to reduce hamstring injury incidence, whilst enhancing physical qualities critical to sport. [ABSTRACT FROM AUTHOR]

During soccer matches, performance decrements have been reported that relate to both physical abilities and technical skills. To investigate the effects of low-frequency electrical stimulation LFES (VeinoplusSport®, Ad Rem Technology, France) administered during half-time recovery on performance alterations during the second half. Twenty-two highly trained young players undertook a soccer-match simulation (SAFT90). During half-time, they were randomly assigned to LFES group or Placebo group. Each half was split into 3 bouts of 12 minutes. Following each bout, maximal strike speed (MSS), sprint test (ST), maximal sprint accelerations (MA) and metabolic power (MP) were determined in both groups. Arterial (AF) and venous flows (VF) were measured at rest and at the end of half-time. LEFS group exhibited beneficial effects on performance compared to the Placebo group with a likely effect for MSS, ST, MA, and a possible effect for MP. AF and VF increased statistically more in LEFS group compared to Placebo group. The use of specific calf-pump LFES during half-time of a youth simulated soccer match attenuated the decrease in performance during the second half compared to Placebo group. This effect is most marked at the beginning of the second half with regards to explosive parameters. [ABSTRACT FROM AUTHOR]

Anterior cruciate ligament (ACL) injury prevention programmes have not been as successful at reducing injury rates in women's basketball as in soccer. This randomised controlled trial (ClinicalTrials.gov #NCT02530333) compared biomechanical adaptations in basketball and soccer players during jumplanding activities after an ACL injury prevention programme. Eighty-seven athletes were cluster randomised into intervention (6-week programme) and control groups. Three-dimensional biomechanical analyses of drop vertical jump (DVJ), double- (SAG-DL) and single-leg (SAG-SL) sagittal, and double- (FRONT-DL) and single-leg (FRONT-SL) frontal plane jump landing tasks were tested before and after the intervention. Peak angles, excursions, and joint moments were analysed using two-way MANCOVAs of post-test scores while controlling for pre-test scores. During SAG-SL the basketball intervention group exhibited increased peak knee abduction angles (p = .004) and excursions (p = .003) compared to the basketball control group (p = .01) and soccer intervention group (p = .01). During FRONT-SL, the basketball intervention group exhibited greater knee flexion excursion after training than the control group (p = .01), but not the soccer intervention group (p = .11). Although women's soccer players exhibit greater improvements in knee abduction kinematics than basketball players, these athletes largely exhibit similar biomechanical adaptations to ACL injury prevention programmes. [ABSTRACT FROM AUTHOR]

The purpose of this systematic review and meta-analysis is to assess the effect of concurrent high intensity interval training (HIIT) and resistance training (RT) on strength and hypertrophy. Five electronic databases were searched using terms related to HIIT, RT, and concurrent training. Effect size (ES), calculated as standardised differences in the means, were used to examine the effect of concurrent HIIT and RT compared to RT alone on muscle strength and hypertrophy. Sub-analyses were performed to assess region-specific strength and hypertrophy, HIIT modality (cycling versus running), and intermodal rest responses. Compared to RT alone, concurrent HIIT and RT led to similar changes in muscle hypertrophy and upper body strength. Concurrent HIIT and RT resulted in a lower increase in lower body strength compared to RT alone (ES = -0.248, p = 0.049). Sub analyses showed a trend for lower body strength to be negatively affected by cycling HIIT (ES = -0.377, p = 0.074) and not running (ES = -0.176, p = 0.261). Data suggests concurrent HIIT and RT does not negatively impact hypertrophy or upper body strength, and that any possible negative effect on lower body strength may be ameliorated by incorporating running based HIIT and longer inter-modal rest periods. [ABSTRACT FROM AUTHOR]

This study examined agreement between self-perceived sleep and sleep estimated via activity monitors in professional rugby league athletes. 63 athletes, from three separate teams wore actigraphy monitors for 10.3 ± 3.9 days. During the monitoring period, ratings of perceived sleep quality (on a 1-5 and 1-10 Likert scale), and an estimate of sleep duration were recorded daily. Agreement between sleep estimated via activity monitors and self-perceived sleep was examined using mean bias, Pearson correlation (r) and typical error of the estimate (TEE). 641 nights of sleep were recorded, with a very large, positive correlation observed between sleep duration estimated via activity monitors and subjective sleep duration (r = 0.85), and a TEE of 48 minutes. Mean bias revealed subjective sleep duration overestimated sleep by an average of 19.8 minutes. The relationship between sleep efficiency estimated via activity monitors and self-perceived sleep quality on a 1-5 (r = 0.22) and 1-10 Likert scale (r = 0.28) was limited. The outcomes of this investigation support the use of subjective measures to monitor sleep duration in rugby league athletes when objective means are unavailable. However, practitioners should be aware of the tendency of athletes to overestimate sleep duration. [ABSTRACT FROM AUTHOR]

Forty-one practitioners inclusive of physiotherapists, sports scientists and strength and conditioning coaches from the academies of elite soccer clubs in the United Kingdom completed an on-line questionnaire which examined their: (1) background information; (2) perceptions of injury occurrence and risk factors; (3) screening and return to play; and (4) approach to designing and delivering injury prevention programmes with a response rate of 55% (41/75). Contact injuries were the most common mechanism reported and players between 13-16 years of age were perceived to be at the greatest risk. Pertinent risk factors included: reduced lower limb and eccentric hamstring strength, proprioception, muscle imbalances, and under developed foundational movement skills. Joint range of motion, jump tests, the functional movement screen, overhead and single leg squats were the most utilised screening methods. Training modalities rated in order of importance included: resistance training, flexibility development, agility, plyometrics and balance training. Training frequency was most commonly once or twice per week, during warm-ups, independent sessions or a combination of both. Injury prevention strategies in this cohort appear to be logical; however, the classification of injury occurrence and application of screening tools to identify “at risk” players do not align with existing research. The frequency and type of training used may also be insufficient to elicit an appropriate stimulus to address pertinent risk factors based on current recommendations. [ABSTRACT FROM AUTHOR]

This study compared children’s physical activity (PA) levels, the prevalence of children meeting current guidelines of ≥60 minutes of daily moderate to vigorous PA (MVPA), and PA-health associations using individually calibrated (IC) and empirical accelerometer cutpoints. Data from 75 (n = 32 boys) 10-12 year old children were included in this study. Clustered cardiometabolic (CM) risk, directly measured cardiorespiratory fitness (CRF), anthropometric and 7 day accelerometer data were included within analysis. PA data were classified using Froude anchored IC, Evenson et al. (Evenson, K. R., Catellier, D. J., Gill, K., Ondrak, K. S., & McMurray, R. G. (2008). Calibration of two objective measures of physical activity for children. Journal of Sports Sciences, 26(14), 1557-1565. doi:10.1080/02640410802334196) (Ev) and Mackintosh et al. (Mackintosh, K. A., Fairclough, S. J., Stratton, G., & Ridgers, N. D. (2012). A calibration protocol for population-specific accelerometer cutpoints in children. PLoS One, 7(5), e36919. doi:10.1371/journal.pone.0036919) (Mack) cutpoints. The proportion of the cohort meeting ≥60mins MVPA/day ranged from 37%-56% depending on the cutpoints used. Reported PA differed significantly across the cutpoint sets. IC LPA and MPA were predictors of CRF (LPA: standardised β = 0.32, p = 0.002, MPA: standardised β = 0.27 p = 0.013). IC MPA also predicted BMI Z-score (standardised β = −0.35, p = 0.004). Ev VPA was a predictor of BMI Z-score (standardised β = −0.33, p = 0.012). Cutpoint choice has a substantial impact on reported PA levels though no significant associations with CM risk were observed. Froude IC cutpoints represent a promising approach towards classifying children’s PA data. [ABSTRACT FROM AUTHOR]