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This study investigated the extent of injury incidence and burden in a professional women football team of the Scottish Women's Premier League during two seasons. All injuries causing time-loss or required medical attention were recorded prospectively. A total of 671 injuries, 570 requiring medical attention and 101 causing time-loss were recorded in 41 players. Injuries occurring with National Team resulted in 12% of the club's international players' lay-off. Overall injury incidence was 11.1/1000-hours and burden was 368.9 days/1000-hours. Injury incidence (23.9/1000-hours vs 8.2/1000-hours) and burden (1049.8 days/1000-hours vs 215.1 days/1000-hours) were higher for match compared to training. Foremost mechanism of match injury burden was indirect-contact, which was different than the non-contact predominantly observed for training injury burden. Injury incidence, burden and patterns differed between training, match and playing positions. Tailoring injury-risk reduction strategies considering context, circumstances and playing position deserve consideration to enhance player's injury resilience in professional women footballers.

Purpose: Global navigation satellite system device-derived metrics are commonly represented by discrete zones with intensity often measured by standardizing volume to per-minute of activity duration. This approach is sensitive to imprecision in duration measurement and can lead to highly variable outcomes-transforming data from zones to a gradient may overcome this problem. The purpose of this study was to critically evaluate this approach for measuring team-sport activity demands., Methods: Data were collected from 129 first-team and 73 academy matches from a Scottish Premiership football club. Gradients were calculated for velocity, acceleration, and deceleration zones, along with per-minute values for several commonly used metrics. Means and 95% CIs were calculated for playing level, as well as first-team positional groups. Within-subject coefficients of variation were also calculated for match level, position, and individual groups., Results: The gradient approach showed consistency with per-minute metrics when measuring playing level and position groups. With coefficients of variation of 10.8% to 26.9%, the gradients demonstrated lower variability than most per-minute variables, which ranged from 10.7% to 84.5%., Conclusions: Gradients are a potentially useful way of describing intensity in team sports and compare favorably to existing intensity variables in their ability to distinguish between match types and position groups, providing evidence that gradient variables can be used to monitor match and training intensity in team sports.

The aim of this review was to critically appraise the literature concerning the genetic association with athlete status, physical performance, and injury risk in soccer. The objectives were to provide guidance on which genetic markers could potentially be used as part of future practice in soccer and to provide direction for future research in this area. The most compelling evidence identified six genetic polymorphisms to be associated with soccer athlete status ( ACE I/D; ACTN3 rs1815739; AGT rs699; MCT1 rs1049434; NOS3 rs2070744; PPARA rs4253778), six with physical performance ( ACTN3 rs1815739; AMPD1 rs17602729; BDNF rs6265; COL2A1 rs2070739; COL5A1 rs12722; NOS3 rs2070744), and seven with injury risk ( ACTN3 rs1815739; CCL2 rs2857656; COL1A1 rs1800012; COL5A1 rs12722; EMILIN1 rs2289360; IL6 rs1800795; MMP3 rs679620). As well as replication by independent groups, large-scale genome-wide association studies are required to identify new genetic markers. Future research should also investigate the physiological mechanisms associating these polymorphisms with specific phenotypes. Further, researchers should investigate the above associations in female and non-Caucasian soccer players, as almost all published studies have recruited male participants of European ancestry. Only after robust, independently replicated genetic data have been generated, can genetic testing be considered an additional tool to potentially inform future practice in soccer., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)

This study investigates variations in skinfold thickness in a European professional football team within and across multiple seasons, including before and after COVID-19 restrictions. Skinfold thickness was measured in 49 male players on 32 occasions across three seasons (2018/19, 2019/20 and 2020/21). Intra- and inter-seasonal trends were examined by comparing values for the sum of eight skinfolds (sum8) at key time points using linear mixed models. In each season, the largest differences in sum8 occurred after the preseason period. These differences ranged from a mean difference (M diff ) of -11.0 mm ( p  < 0.001) in 2018/19 to -4.8 mm ( p  < 0.001) in 2020/21. Increases in sum8 occurred after each off-season; however, the increase after the off-season before the 2020/21 season (which included the COVID-19 lockdown period) was the lowest in magnitude and was not statistically significant (M diff  = 2.9 mm, p  = 0.06). Changes occurring in sum8 between the start and end of the competitive season did not follow a consistent pattern and were generally smaller in magnitude than the changes between other seasonal time points. Despite the notable heterogeneity in sum8 between players, changes within players generally followed a similar pattern between the different seasonal timepoints. In summary, changes in skinfold thickness were predominantly related to off-season and 'preparation for competition' periods. Increases in skinfold thickness can be mitigated during extended remote training periods with appropriate training and nutritional strategies.

Aim: To describe and compare the peak physical demands through the worst-case scenario method (WCS), according to different rolling average (RA) time epochs (i.e. 1 min, 3 min, and 5 min) and contextual variables in women soccer players. Methods: Using an observational-comparative study design, an elite women soccer team from the Spanish 1 st league division was monitored during 27 matches. Nine WCS-dependent variables were assessed, including total distance (TD), high-speed running distance (HSR), sprint distance (SP), acceleration, and deceleration distance at different intensities by players position (i.e., central defenders [CD], wide defenders [WD], central midfielders [CM], wide midfielders [WM], forwards [F]), match half, location, and match outcome. Results: The 1-min RA showed the lowest variability (CV = 9.8-65.8%) for all nine dependent variables. The WD presented the highest TD (168 ± 15.71 m/min). Differences between positions were observed for: CM

Professional soccer players typically perform regular training sessions and match play for most of the yearly macrocycle with limited time focused on solely developing physical development. The COVID-19 outbreak in 2020 caused mass disruption to professional soccer but provided an opportunity for an alternative approach to training in attempt to develop professional soccer players physical fitness levels. In a non-randomised and non-controlled study, we aimed to assess the effectiveness of a 13-week remote based physical training programme on physical fitness levels in elite professional soccer players. Twenty professional soccer players undertook body composition assessments, a countermovement jump (CMJ) test, eccentric hamstring strength test and a submaximal 30-15 intermittent fitness test (IFT) pre- and post-remote based training programme. Body mass (79.3 ± 6.7 vs. 80.0 ± 7.3 kg), skinfold thickness (54.1 ± 14.8 vs. 56.7 ± 15.2 mm), maximum CMJ height (38.4 ± 3.4 vs. 40.9 ± 4.1 cm), eccentric hamstring strength (1035 ± 158 vs. 1009 ± 140 n) and percentage max heart rate reached in submaximal 30-15 IFT (81.3 ± 5.2 vs. 82.3 ± 7.3%) were maintained (all P > 0.05) from pre- to post training programme, respectively. Although team-based soccer specific training load was removed, and the training programmes prescribed had an increased physical focus, fitness levels were maintained. This suggests that alternative modes of training can potentially be used in instances where team-based soccer specific training load isn't required or is unavailable, without negatively impacting physical development., (© The Author(s) 2022.)

In elite football, the emphasis is placed on monitoring the output from the Global Positioning Systems (GPS) component of a Micro-Electro-Mechanical Systems (MEMS) device; however, this does not comprehensively overview the total demands due to the intermittent multidirectional nature. The aim of the study was to investigate the application of accelerometer data provided by MEMS, to evaluate movement requirements in elite football. A two-staged research approach, involving an effectiveness and efficacy stage, was deployed. The effectiveness stage examined two MEMS-accelerometer variables (PlayerLoad TM (PL) and PlayerLoad TM per meter (PL.m -1 )) for four years and four months. Ninety-nine English Premier League outfield football players' participated. In the efficacy stage, 26 elite outfield football players completed three different training modalities (running, possession and dribbling) and a range of MEMS-accelerometer variables were analysed. In the effectiveness stage, the mean difference in PL for all training activities other than Set Pieces were similar to Matches (-283 to -246au). Model coefficients for PL.m -1 were smallest in Team Shape (-0.00114au), Attacking (0.00025au) and Games (0.00196au), and largest for Possession (0.03356AU), Defending (0.03182au) and Skills Games (0.03106au) compared to Matches. The findings suggest that PL.m -1 but not PL may be effective at describing differences in movement requirements. In the efficacy stage, PL.m -1 and inertial movement analysis (IMA) efforts were the only variables that had greater mean differences in the smaller conditions, confirming PL.m -1 's suitability in evaluating movement requirements of different training activities and pitch dimensions. The findings suggest such a variable offers value in a monitoring strategy in football.

Background: The SARS-CoV-2 agent initiated a global pandemic. The initial response to the pandemic was severe disruption to the public and private sector including sports. The resultant was that soccer clubs had to prescribe that the players trained in isolation for a prolonged period of time in an attempt to maintain fitness. The aim of the present study was to evaluate the impact of a 10-week period of training in isolation on aerobic fitness, body composition and injury incidence on the return to preseason team-training in a group of elite, male soccer players., Methods: Twenty-two professional soccer players (age: 25.2±4.4 years) who played for an English Championship first team participated in this study. A weekly training program was sent to each player at the start of each week. Prior to the start of the isolated training period, all players underwent a maximal aerobic speed test (MAS), and Body Mass Index data (BMI) were obtained. These measurements were repeated on the return to team training., Results: There was a significant (P<0.05) increase in MAS pre-post isolated training (pre: 4.71±0.15 vs. post: 4.92±0.17 m/s), no change in BMI (pre: 24.3±1.3 vs. post: 24.1±1.1 kg/m 2 ) and a low non-contact, soft-tissue injury incidence on the return to team training., Conclusions: The evidence from this study suggests that a more prolonged preseason schedule can enhance aerobic conditioning and mitigate the injury risk on the return to competitive match-play in elite soccer players.

Purpose: This study aimed to examine the responsiveness of commonly used measurement instruments to a short training camp by examining the time course of psychophysiological responses in high-level youth soccer players., Methods: Monitoring was carried out in 14 U15 male soccer players of 1 professional youth academy. Players provided data 3 days prior to (D - 3), during (D2-D4), and 1 (D + 1) and 4 days (D + 4) after the camp: 4 items for the Short Recovery and Stress Scale (SRSS), a countermovement jump (CMJ), and a submaximal run to assess exercise heart rate and heart-rate recovery. Training load during the camp followed an alternating low-high pattern, with lower training loads on D1 and D3 and higher training loads on D2 and D4., Results: Changes in SRSS physical performance capability, emotional balance, overall recovery, muscular stress, and overall stress were small to moderate on D3 and moderate to large on D + 1, while changes were trivial on D + 4. Some CMJ parameters related to the eccentric phase were slightly improved on D3, and these parameters were slightly impaired on D4. Changes in CMJ parameters were trivial on D + 1 and D + 4. After a moderate decrease in exercise heart rate on D3, there was a small decrease on D + 4 and a moderate increase in heart-rate recovery., Conclusion: Measurement instruments such as the SRSS and submaximal runs can be used to monitor acute psychophysiological responses to load, while the CMJ may provide little insight during periods of intensified training load.

The purpose of this study was to present reference standards for physical performance test outcomes relevant to elite female soccer players. We analysed mixed-longitudinal data (n = 1715 observations) from a sample of 479 elite youth and senior players as part of the English Football Association's national development programme (age range: 12.7 to 36.0 years). Semi-parametric generalized additive models for location, scale and shape (GAMLSS) estimated age-related reference centiles for 5-m sprinting, 30-m sprinting, countermovement jump (CMJ) height, and Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) performance. The estimated reference centiles indicated that the median of the distribution of physical performance test scores varied non-linearly with advancing chronological age, improving until around 25 years for each performance variable. These are the first reference ranges for performance test outcomes in elite English female soccer players. These data can assist practitioners when interpreting physical test performance outcomes to track an individual's progress over time and support decision-making regarding player recruitment and development.

Purpose: The aim of this study was to investigate the frequency of change of directions (COD) and examine the influences of position, leg dominance and anthropometrics on COD in elite youth soccer match play., Methods: Twenty-four elite male English Premier League (EPL) academy players (19.0 ± 1.9 years) were individually recorded during ten competitive U18s and U23s matches. Video footage of individual players was analysed using a manual notation system to record COD frequency, direction, estimated angle and recovery time. The influences of position, anthropometrics and leg dominance were accounted for., Results: Elite youth soccer players performed on average 305 ± 50 CODs with on average 19.2 ± 3.9 seconds of recovery. The frequency of CODs was independent of position, leg dominance, anthropometry and occurred equally between left and right direction and forwards and backwards direction. CODs were mostly ≤90° (77%) and there were significantly less CODs in the 2 nd half (-29, ES  = 1.23, P < 0.001). The average and peak within match demands within 15 and 5-minute periods were 49 and 62 CODs, and 16 and 25 CODs, respectively., Conclusion: This study is the first to illustrate COD frequencies of elite youth soccer match play, providing practitioners guidance to prepare soccer players for competitive match demands.

Context: Whether playing position influences injury in male academy soccer players (ASPs) is unclear., Objective: To determine if playing position was associated with injury in ASPs., Design: Descriptive epidemiology study., Setting: English, Spanish, Uruguayan, and Brazilian soccer academies., Patients or Other Participants: A total of 369 ASPs from the under-14 to under-23 age groups, classified as post-peak height velocity using maturity offset, and grouped as goalkeepers, lateral defenders, central defenders, lateral midfielders, central midfielders, or forwards., Main Outcome Measure(s): Injuries were recorded prospectively over 1 season. Injury prevalence proportion (IPP), days missed, and injury incidence rate (IIR, injuries/1000 training or match hours, n = 116) were analyzed according to playing position., Results: No association with playing position was observed for any injury type or location regarding IPP (P ≥ .089) or days missed (P ≥ .235). The IIR was higher in central defenders than in lateral defenders for general (9.30 versus 4.18 injuries/1000 h, P = .009), soft tissue (5.14 versus 1.95 injuries/1000 h, P = .026), and ligament or tendon injuries (2.69 versus 0.56 injuries/1000 h, P = .040). The central versus lateral or forward positions were not associated with IPP (P ≥ .051) or days missed (P ≥ .083), but general IIR was greater in the central position than the lateral or forward positions (8.67 versus 6.12 injuries/1000 h, P = .047)., Conclusions: Academy soccer players' playing positions were not associated with IPP or days missed, but the higher general, soft tissue, and ligament or tendon IIRs in central defenders suggest that this position warrants specific attention regarding injury-prevention strategies. These novel findings highlight the importance of considering training or match exposure when investigating the influence of playing position on injury in ASPs., (© by the National Athletic Trainers' Association, Inc.)

We investigated whether 20 candidate single nucleotide polymorphisms (SNPs) were associated with in vivo exercise-induced muscle damage (EIMD), and with an in vitro skeletal muscle stem cell wound healing assay. Sixty-five young, untrained Caucasian adults performed 120 maximal eccentric knee-extensions on an isokinetic dynamometer to induce EIMD. Maximal voluntary isometric/isokinetic knee-extensor torque, knee joint range of motion (ROM), muscle soreness, serum creatine kinase activity and interleukin-6 concentration were assessed before, directly after and 48 h after EIMD. Muscle stem cells were cultured from vastus lateralis biopsies from a separate cohort (n = 12), and markers of repair were measured in vitro. Participants were genotyped for all 20 SNPs using real-time PCR. Seven SNPs were associated with the response to EIMD, and these were used to calculate a total genotype score, which enabled participants to be segregated into three polygenic groups: 'preferential' (more 'protective' alleles), 'moderate', and 'non-preferential'. The non-preferential group was consistently weaker than the preferential group (1.93 ± 0.81 vs. 2.73 ± 0.59 N ∙ m/kg; P = 9.51 × 10 -4 ) and demonstrated more muscle soreness (p = 0.011) and a larger decrease in knee joint ROM (p = 0.006) following EIMD. Two TTN-AS1 SNPs in linkage disequilibrium were associated with in vivo EIMD (rs3731749, p ≤ 0.005) and accelerated muscle stem cell migration into the artificial wound in vitro (rs1001238, p ≤ 0.006). Thus, we have identified a polygenic profile, linked with both muscle weakness and poorer recovery following EIMD. Moreover, we provide evidence for a novel TTN gene-cell-skeletal muscle mechanism that may help explain some of the interindividual variability in the response to EIMD., (© 2022 The Authors. Journal of Cellular Physiology published by Wiley Periodicals LLC.)

Purpose: The aim of this study was to assess the short-term responsiveness of measurement instruments aiming at quantifying the acute psycho-physiological response to load in high-level adolescent soccer players., Methods: Data were collected from 16 high-level male youth soccer players from the Under 15 age group. Players were assessed on two occasions during the week: after 2 days of load accumulation ("high load") and after at least 48 h of rest. Measurements consisted of the Short Recovery and Stress Scale (SRSS), a countermovement jump (CMJ) and a sub-maximal run to assess exercise heart-rate (HRex) and heart-rate recovery (HRR60s). Training load was quantified using total distance and high-speed running distance to express external and sRPE training load to express internal load. It was expected that good instruments can distinguish reliably between high load and rest., Results: Odd ratios (0.74-1.73) of rating one unit higher or lower were very low for athlete-reported ratings of stress and recovery of the SRSS. Standardized mean high load vs. rest differences for CMJ parameters were trivial to small (-0.31 to 0.34). The degree of evidence against the null hypothesis that changes are interchangeable ranged from p = 0.04 to p = 0.83. Moderate changes were observed for HRex (-0.62; 90% Cl -0.78 to -0.47; p = 3.24 × 10 -9 ), while small changes were evident for HRR60s (0.45; 90% Cl 0.08-0.80; p = 0.04). Only small to moderate repeated-measures correlations were found between the accumulation of load and acute responses across all measurement instruments. The strongest relationships were observed between HRex and total distance (rm-r = -0.48; 90% Cl -0.76 to -0.25)., Conclusion: Results suggest that most of the investigated measurement instruments to assess acute psycho-physiological responses in adolescent soccer players have limited short-term responsiveness. This questions their potential usefulness to detect meaningful changes and manage subsequent training load and program adequate recovery., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ruf, Drust, Ehmann, Skorski and Meyer.)

Introduction: Valid and informed interpretations of changes in physical performance test data are important within athletic development programmes. At present, there is a lack of consensus regarding a suitable method for deeming whether a change in physical performance is practically relevant or not., Methods: We compared true population variance in mean test scores between those derived from evidence synthesis of observational studies to those derived from practioner opinion (n = 30), and to those derived from a measurement error (minimal detectable change) quantification (n = 140). All these methods can help to obtain 'target' change score values for performance variables., Results: We found that the conventional 'blanket' target change of 0.2 (between-subjects SD) systematically underestimated practically relevant and more informed changes derived for 5-m sprinting, 30-m sprinting, CMJ, and Yo-Yo Intermittent Recovery Level 1 (IR1) tests in elite female soccer players., Conclusions: For the first time in the field of sport and exercise sciences, we have illustrated the use of a principled approach for comparing different methods for the definition of changes in physical performance test variables that are practically relevant. Our between-method comparison approach provides preliminary guidance for arriving at target change values that may be useful for research purposes and tracking of individual female soccer player's physical performance.

Objectives: To investigate if maturity status was associated with injury risk in male academy soccer players., Design: Prospective cohort surveillance study., Setting: Professional soccer academies., Participants: 501 players (aged 9-23 years) from eight academies in England, Spain, Uruguay and Brazil., Main Outcome Measures: Players were grouped by maturity offset as pre-peak height velocity (PHV), circa-PHV, post-PHV or adult. Injury prevalence proportion (IPP) and days missed were recorded for one season per player, with training/match exposure recorded in a sub-sample (n = 166)., Results: IPP for all injuries combined increased with advancing maturity, with circa-PHV (p = 0.032), post-PHV (p < 0.001) and adult (p < 0.001) higher than pre-PHV. IPP was higher in post-PHV and adult than pre-PHV for non-contact (p = 0.001 and p = 0.012), soft-tissue (both p < 0.001), non-contact soft-tissue (p < 0.001 and p = 0.005), muscle (both p < 0.001), thigh (both p < 0.001), ankle (p = 0.035 and p = 0.007) and hamstring injuries (p = 0.041 and p = 0.017). Ligament/tendon IPP was greater in adult versus pre-PHV (p = 0.002). IPP for growth-related injuries was lower in post-PHV than pre-PHV (p = 0.039). Injury incidence rates (n = 166) exhibited similar patterns to IPP in the full cohort., Conclusions: Injury patterns were similar between post-PHV and adult academy players but, crucially, relatively more of these groups suffered injuries compared to pre- and circa-PHV (except growth-related injuries)., Competing Interests: Declaration of competing interest The authors declare no conflict of interest, financial or otherwise, related to the preparation of this manuscript. This study was funded as part of a University PhD scholarship., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

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.

It is currently unknown if injury risk is associated with genetic variation in academy soccer players (ASP). We investigated whether nine candidate single nucleotide polymorphisms were associated (individually and in combination) with injury in ASP at different stages of maturation. Saliva samples and one season's injury records were collected from 402 Caucasian male ASP from England, Spain, Uruguay, and Brazil, whose maturity status was defined as pre- or post-peak height velocity (PHV). Pre-PHV COL5A1 rs12722 CC homozygotes had relatively higher prevalence of any musculoskeletal soft tissue (22.4% vs. 3.0%, p = 0.018) and ligament (18.8% vs. 11.8%, p = 0.029) injury than T-allele carriers, while VEGFA rs2010963 CC homozygotes had greater risk of ligament/tendon injury than G-allele carriers. Post-PHV IL6 rs1800795 CC homozygotes had a relatively higher prevalence of any (67.6% vs. 40.6%, p = 0.003) and muscle (38.2% vs. 19.2%, p = 0.013) injuries than G-allele carriers. Relatively more post-PHV EMILIN1 rs2289360 CC homozygotes suffered any injury than CT and TT genotypes (56.4% vs. 40.3% and 32.8%, p = 0.007), while the "protective" EMILIN1 TT genotype was more frequent in post- than pre-PHV ASP (22.3 vs. 10.0%, p = 0.008). Regardless of maturity status, T-alleles of ACTN3 rs1815739 and EMILIN1 rs2289360 were associated with greater absence following ankle injury, while the MMP3 rs679620 T-allele and MYLK rs28497577 GT genotype were associated with greater absence following knee injury. The combination of injury-associated genotypes was greater in injured vs. non-injured ASP. This study is the first to demonstrate that a genetic association exists with injury prevalence in ASP, which differs according to maturity status., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Abstract: Beato, M, Bianchi, M, Coratella, G, Merlini, M, and Drust, B. A single session of straight line and change-of-direction sprinting per week does not lead to different fitness improvements in elite young soccer players. J Strength Cond Res 36(2): 518-524, 2022-Effective prescription is especially important in elite soccer players, who have a very limited time to dedicate to specific physical development as a consequence of factors such as congested match schedules and travel. The aim of this study was to compare the effectiveness of one repeated-sprint training (RST) session per week over an 8-week period on physical performance. A second aim was to compare the effect of RST involving straight sprints (RST-SS) or changes of direction (RST-COD). This study used a randomized pre-post parallel group trial design. The elite soccer players were randomly assigned to either an RST-SS (10 players) or RST-COD (10 players). RST-SS was 3 sets of 7 × 30-m sprints with 20-second and 4-minute recovery between sprints and sets, respectively. RST-COD was 3 sets of 7 × 20 + 20 m (one COD of 180°) shuttle sprints with 20-second and 4-minute recovery between sprints and sets, respectively. The physical tests selected were long jump, repeated-sprint ability (RSA) best, RSA mean, 505 agility test, Yo-Yo recovery level 1, 10, 30, and 40 m sprints. RST-SS reported unclear variations in long jump, sprint 30 m, sprint 40 m, RSA best, and RSA mean, whereas RST-COD showed unclear and trivial variations in sprint 10 m, sprint 30 m, sprint 40 m, RSA best, and RSA mean. The between-group analysis did not report any statistical difference. In conclusion, a single session of RST-SS and RST-COD do not improve soccer-specific fitness indicators in elite youth players during the season., (Copyright © 2019 National Strength and Conditioning Association.)

Purpose: To assess the short-term reliability of measurement instruments to quantify the acute psychophysiological response to load in adolescent soccer players in relation to biological maturity., Methods: Data were collected from 108 U12 to U17 soccer players on 2 consecutive weeks (pre, n = 32; at, n = 34; and post, n = 42 estimated peak height velocity). Measurements consisted of the Short Recovery and Stress Scale, a countermovement jump, assessment of leg stiffness, and a submaximal run to assess exercise heart rate and heart rate recovery. Test-retest reliability was assessed with the coefficient of variation (CV) and intraclass correlation coefficient (ICC)., Results: Items of the Short Recovery and Stress Scale showed poor reliability across maturity groups (CV = 7.0%-53.5%; ICC = .28 to .79). Only few countermovement jump variables (jump height, concentric impulse, and concentric velocity) possessed good reliability. For most variables of the countermovement jump, reliability was better for the post peak height velocity group followed by at-peak height velocity and prepeak height velocity. Very high levels of reliability across maturity groups were observed for exercise heart rate (CV < 1.8%; ICC > .94), while heart rate recovery was more variable (CV < 16.5%; ICC > .48)., Conclusion: Results suggest that the majority of investigated variables have poor reliability, questioning their ability to detect small, yet meaningful changes in acute responses to load in adolescent soccer players.

Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Sport Science is considered the study and application of scientific principles and techniques to improve sporting performance. Thus, a key role of the Sport Scientist is to translate complex information into usable and contextual performance solutions for a range of different stakeholders. These stakeholders consist of athletes, coaches, recruiting, performance support, medical, administration and operations staff and have varying interests and priorities meaning the information required can be vastly different. In addition to these different needs, sport is fast-moving, diverse and complex meaning there are a number of potential translational barriers. Sport Science training programmes entail the development of technical knowledge and practical skills; however, little is considered in view of interpersonal craft skill development and knowledge translation (KT). Given the reported barriers and challenges to effective KT in sport, this lack of specific training may render KT as ineffective and suboptimal. Accordingly, in this article, we propose a framework and work-based training model with the aim of developing the KT process and performance delivery of Sport Scientists operating in professional sport. Firstly, we define the current perspectives and challenges for Sport Scientists in the context of KT, before proposing a framework that focusses on Evidence-Based-Practice, Philosophy, Recipients and Facilitation, in which Sport Scientists can use to develop their interpersonal craft and subsequent KT approach. We finish by presenting a model of sport science practitioner training; the professional sport-doctoral training programme, that combined with the framework, can be effective in developing Sport Scientists.