The acute effect of match play on hamstring strength and lower limb flexibility in elite youth football players

Post-game recovery of isometric hamstring strength in a high-risk hamstring strain injury group throughout an Australian Football League season

This study sought to investigate post-game hamstring strength recovery of 26 Australian Football League (AFL) players with a previous hamstring strain injury (HSI) across an AFL season. Maximal unilateral isometric knee flexion strength was assessed using an externally fixed dynamometer, and inter-session reliability was measured during the pre-season period. Linear mixed effects models investigated the influence of numerous variables on post-game hamstring strength decrement (relative change between initial weekly test and individual baseline) and individual within-week strength change following gameplay. The test demonstrated good inter-tester reliability (ICC = 0.81-0.88; CV = 6.73-7.33), and an acceptable level of error (MAE = 5.77-7.14%). Player as a random effect strongly influenced post-game strength decrement and within-week strength change (marginal R2 = 0.185-0.407; conditional R2 = 0.455-0.654). Within-week hamstring strength change was strongly determined by post-game strength decrement alone (estimate = 0.51, 95% CI = -0.66- -0.36 ; η2 = 0.32; P=<0.001) and in interaction with number of days post-game (estimate = 0.43, 95% CI = 0.20-0.66; η2 = 0.096; P=<0.001). This study shows the importance of early individual assessment of post-game hamstring strength in players with prior hamstring injury and could be valuable to inform post-game hamstring recovery in future applications.

Using Bar Velocity to Assess Post-match Neuromuscular Fatigue in Young Soccer Players

This study aimed to investigate the recovery of neuromuscular performance using mechanical parameters collected during jump (vertical and horizontal) and strength-power exercises in youth soccer players after official soccer matches. Twenty-one outfield highly trained youth male soccer athletes (age: 18.23±0.73 years; weight: 72.12±6.99 kg; height: 1.78±0.08 m) from two teams competing in the 1st division of U-19 Portuguese National Championship participated in this study. Players completed a battery of physical tests at -2 h, + 30 min, +24 h, and +48 h in relation to the match. Countermovement jump height, horizontal jump distance, and bar velocity during the half squat, bench press, and hip thrust exercises, at fixed loads, were recorded. Countermovement jump was impaired until 24 h post-match (-: 1.7% from pre- to 24 h post-match, p=0.050; ES=-: 0.82). Half-squat bar velocity was reduced immediately following the match (-: 6.8% from pre-match, p=0.004; ES=-: 0.64) but recovered at +24 h (+2.9%, p=1.00; ES=0.02). Hip-thrust bar velocity was reduced for up to 48 h post-match (-: 7.4% from pre- to 48 h post-match, p<0.001; ES=-: 0.80). No impairments were found in the horizontal jump and bench press at any moment. Our findings show prolonged decrements in strength of the posterior chain following a soccer match, measured in the hip thrust exercise, while the other exercises displayed faster recovery dynamics.

Rapid force generation during unilateral isometric hamstring assessment: reliability and relationship to maximal force

Limited research has reported the reliability of rapid force generation characteristics during isometric assessments of the hamstrings. Therefore, the purpose of the present study was to determine the between-session reliability of rapid force generating characteristics of the hamstrings and relationship to maximal force production. Twenty-three female soccer players (age: 20.7 ± 4.7 years; height: 168.7 ± 5.9 cm; body mass: 64.4 ± 6.7 kg) performed three unilateral trials of the 90-90 isometric hamstring assessment, on two separate occasions, separated by 7 days. Peak force, force at 100- and 200 ms and average rate of force development (aRFD) over 100- and 200 ms epochs were calculated. Absolute and fair-good reliability was observed for peak force and all rapid force generating measures (<8.33CV%, ICC >0.610). Significant and meaningful relationships (p < 0.001, r > 0.802) were observed for all rapid force generating measures and peak force. The 90-90 isometric assessment can be used to assess peak and rapid force generating reliably to enable practitioners to confidently track changes in performance over time as part of fatigue monitoring and management.

Effects of muscle fatigue on exercise-induced hamstring muscle damage: a three-armed randomized controlled trial

PURPOSE

Hamstring injuries in soccer reportedly increase towards the end of the matches' halves as well as with increased match frequency in combination with short rest periods, possibly due to acute or residual fatigue. Therefore, this study aimed to investigate the effects of acute and residual muscle fatigue on exercise-induced hamstring muscle damage.

METHODS

A three-armed randomized-controlled trial, including 24 resistance-trained males, was performed allocating subjects to either a training group with acute muscle fatigue + eccentric exercise (AF/ECC); residual muscle fatigue + eccentric exercise (RF/ECC) or a control group with only eccentric exercise (ECC). Muscle stiffness, thickness, contractility, peak torque, range of motion, pain perception, and creatine kinase were assessed as muscle damage markers pre, post, 1 h post, and on the consecutive three days.

RESULTS

Significant group × time interactions were revealed for muscle thickness (p = 0.02) and muscle contractility parameters radial displacement (Dm) and contraction velocity (Vc) (both p = 0.01), with larger changes in the ECC group (partial η2 = 0.4). Peak torque dropped by an average of 22% in all groups; stiffness only changed in the RF/ECC group (p = 0.04). Muscle work during the damage protocol was lower for AF/ECC than for ECC and RF/ECC (p = 0.005).

CONCLUSION

Hamstring muscle damage was comparable between the three groups. However, the AF/ECC group resulted in the same amount of muscle damage while accumulating significantly less muscle work during the protocol of the damage exercise.

TRIAL REGISTRATION

This study was preregistered in the international trial registration platform (WHO; registration number: DRKS00025243).

Reliability and sensitivity to change of post-match physical performance measures in elite youth soccer players

Introduction

To effectively monitor post-match changes in physical performance, valid, reliable and practical measures which are sensitive to change are required. This study aimed to quantify test-retest reliability and sensitivity to change of a range of physical performance measures recorded during an isometric posterior chain (IPC) lower-limb muscle test and a countermovement jump (CMJ) test.

Methods

Eighteen Italian Serie A academy soccer players performed three IPC repetitions per limb and five CMJ trials in 4 testing sessions. Test-retest reliability was evaluated between two testing sessions seven days apart using typical error of measurement, coefficient of variation and intraclass correlation coefficient. Sensitivity to change was assessed on two additional testing sessions performed before and immediately after a soccer match through Hedges' g effect size (g) and comparisons to typical error.

Results

Absolute reliability (coefficient of variations) ranged from 1.5 to 8.8%. IPC and CMJ measures demonstrated moderate to excellent relative reliability (intraclass correlation coefficients ranged from 0.70 to 0.98). A wide range of physical performance measures showed significant alterations post-match (p < 0.05; g: small to moderate). IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric forces (mean breaking force, mean deceleration force, peak force, force at zero velocity) and CMJ mean power measures had post-match changes greater than their typical variation, demonstrating acceptable sensitivity in detecting performance changes at post-match.

Discussion

IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric phase forces and CMJ mean power were found to be both reliable and sensitive to change, and thus may be appropriate for monitoring post-match neuromuscular performance in youth soccer population.

Alterations in biceps femoris long head fascicle length, Eccentric hamstring strength qualities and single-leg hop distance throughout the ninety minutes of TSAFT90 simulated football match

INTRODUCTION

Football matches show higher hamstring strain injuries (HSIs) than football training. The occurrence of HSIs increases in the last fifteen minutes of both halves of football matches and shows an incremental trend towards the end of the ninety minutes.

OBJECTIVES

This study aimed to examine football-specific fatigue-induced alterations in risk factors of the HSIs, including biceps femoris long head fascicle length via ultrasonography (BFlh FL), single-leg hop distance, hamstrings' maximal eccentric strength, and single-leg hamstring bridge test (SLHB) performance.

METHODOLOGY

During ninety minutes of the TSAFT90 football simulation, the BFlh FL and single-leg hop distance were measured three times (before, at half-time and after 90 minutes of simulated match-play), and maximal hamstrings eccentric strength and SLHB test scores were recorded twice (before and after simulated match-play) for both legs in physically active participants (n = 15).

RESULTS

Maximal eccentric hamstrings' strength (dominant leg (D): p < 0.001, Hedges' (adjusted) g effect size = -0.969; non-dominant leg (ND): p < 0.001, g = -0.929) and the SLHB performance (D: p < 0.001, g = -1.249; ND: p < 0.001, g = -1.108) showed large decrements immediately after the TSAFT90 intervention. There were no significant alterations in the BFlh FL, and the single-leg hop distance.

CONCLUSIONS

Maximal eccentric strength and the SLHB performance of hamstrings are reduced after 90 minutes of simulated football match-play. Practitioners may consider focusing on improving eccentric strength and the SLHB performance. Future studies should examine alterations in the BFlh fascicles' dynamic lengthening and shortening ability during a football match.

Impact of Flexibility on Vertical Jump, Balance and Speed in Amateur Football Players

Muscle strength, power, balance and speed assume decisive roles in football performance. This study aims to investigate whether lower limb flexibility, particularly the hip flexors and knee extensor and flexor muscles, are correlated with vertical jump performance, balance and speed in adult football players. A sample of 22 male amateur football players (age: 22.3 ± 3 years; height: 175.4 ± 7.4 cm; weight: 74.9 ± 11.6 kg; BMI: 24.2 ± 2.6 kg/m2) were assessed for lower limb flexibility, vertical jump, balance and speed. Results indicated that vertical jump ability is moderately correlated with left knee extensors flexibility (ρ = −0.426; p = 0.048), which did not occur on the right side. There were no statistically significant correlations between vertical jump and knee flexors flexibility (ρ = 0.330; p = 0.133). In balance, the reaching distance on the right side presented a moderate and statistically significant correlation with the knee flexors flexibility (ρ = 0.411; p = 0.040), which was not observed on the left side. Velocity was not correlated with the knee extensors flexibility (right: ρ = 0.360; p = 0.100; left: ρ = 0.386; p = 0.076), or with the knee flexors flexibility (ρ = −0.173; p = 0.440). In conclusion, the influence of flexibility on vertical jump ability, balance and speed appears to exist. Further research should seek to clarify the associations between these abilities.

Effects of Football Training and Match-Play on Hamstring Muscle Strength and Passive Hip and Ankle Range of Motion during the Competitive Season

Deficits in hamstring muscle strength and in hip range of motion (ROM) have been considered risk factors for hamstring muscle injuries. However, there is a lack of information on how chronic exposure to regular football training affects hamstring muscle strength and hip ROM. The aim of this study was to examine the longitudinal effect of football training and competition during a complete season on hamstring muscle strength and hip ROM in football players. A total of 26 semi-professional football players underwent measurements of isometric hamstring muscle strength and passive hip flexion/extension, and internal/external hip rotation (IR/ER) ROM during the football season (pre-season, mid-season, end-season). Compared to pre-season, hamstring muscle strength increased in the dominant (+11.1%, p = 0.002) and non-dominant (+10.5%, p = 0.014) limbs in the mid-season. Compared to mid-season, hamstring strength decreased in the dominant (−9.3%, p = 0.034) limb at end-season. Compared to the pre-season, hip extension ROM decreased in mid-season in the dominant (−31.7%, p = 0.007) and non-dominant (−44.1%, p = 0.004) limbs, and further decreased at end-season (−49.0%, p = 0.006 and −68.0%, p < 0.001) for the dominant and non-dominant limbs. Interlimb asymmetry for hip IR ROM increased by 57.8% (p < 0.002) from pre-season to mid-season. In summary, while hamstring muscle strength increased during the first half of the football season in football players, a progressive reduction in hip extension ROM was observed throughout the season. The reduced hip extension ROM suggests a reduced mobility of the hip flexors, e.g., iliopsoas, produced by the continuous practice of football. Consequently, hip-specific stretching and conditioning exercises programs should be implemented during the football season.

Influence of Football Match-Play on Isometric Knee Flexion Strength and Passive Hip Flexion Range of Motion in Football Referees and Assistant Referees

The aim of this study was to examine the acute effect of officiating a football (soccer) match on isometric knee flexion strength and passive hip flexion range-of-motion (ROM) in referees and assistant football referees. Twelve referees (25.3 ± 3.3 years) and twenty-three assistant referees (25.1 ± 4.8 years) underwent measurements on isometric knee flexion strength and passive hip flexion ROM before and after officiating an official football match. Referees’ and assistant referees’ running patterns were monitored during the match using GPS technology. In comparison to pre-match values, referees reduced their isometric knee flexion strength (−12.36%, p = 0.046, Effect size [ES] = −0.36) in the non-dominant limb, while no significant differences were reported in the dominant limb (−0.75%, p = 0.833, ES = −0.02). No effect of the match was found in hip flexion ROM values in dominant (−4.78%, p = 0.102, ES = −0.15) and non-dominant limb (5.54%, p = 0.544, ES = 0.19). In assistant referees, the pre-to-post-match changes in isometric knee flexion strength (dominant limb −3.10%, p = 0.323, ES = −0.13; non-dominant limb −2.18%, p = 0.980, ES= 0.00) and hip flexion ROM (dominant limb 1.90% p = −0.816, ES = 0.13; non-dominant limb 3.22% p = 0.051, ES = 0.23) did not reach statistical significance. Officiating a match provoked a reduction in isometric knee flexion strength in the non-dominant limb of football referees, while no differences were reported in assistant referees.

Post-match recovery of eccentric knee flexor strength in male professional football players

OBJECTIVES

This study aimed at verifying the effect of a football match on the eccentric knee flexor strength of male professional players along a 72-h period.

STUDY DESIGN

Quasi-experimental study.

SETTING

Football club facilities.

PARTICIPANTS

Fifteen players were assessed in four timepoints: 24 h before, immediately after, 48 h and 72 h after the match.

MAIN OUTCOME MEASURES

The eccentric knee flexor strength was assessed during the Nordic hamstring exercise execution.

RESULTS

Players presented a significant strength reduction immediately after match (Δ = 12%; p = 0.001; large effect size, d = 1.10), and did not recover their strength capacity within a 48 h-period (Δ = 6%; p = 0.011; moderate effect size, d = 0.57). At 72 h after the match, strength was similar to baseline levels (Δ = 3.5%; p = 0.122; small effect size, d = 0.34). Secondarily, individual response analysis considered a player 'fully recovered' when his strength deficit compared to the baseline measure was lower than the measurement coefficient of variation (i.e., <5%). Only 6 (40%) and 9 (60%) players were 'fully recovered' at 48 h and 72 h after the match, respectively.

CONCLUSION

Professional football players experienced an immediately post-match drop on the eccentric knee flexor strength, and significant strength deficits persisted for a 48-h period. Some players were not recovered at 72 h after the match.

Effect of a Simulated Match on Lower Limb Neuromuscular Performance in Youth Footballers-A Two Year Longitudinal Study

The aim of this study was to explore the effects of simulated soccer match play on neuromuscular performance in adolescent players longitudinally over a two-year period. Eleven players completed all measurements in both years of the study (1st year: age 16.0 ± 0.4 y; stature 178.8 ± 6.4 cm; mass 67.5 ± 7.8 kg; maturity-offset 2.24 ± 0.71 y). There was a significant reduction in hamstring strength after simulated match by the soccer-specific aerobic field test (SAFT⁹⁰), with four out of eight parameters compromised in U16s (4.7–7.8% decrease) and six in the U17s (3.1–15.4%). In the U17s all of the concentric quadriceps strength parameters were decreased (3.7–8.6%) as well as the vastus lateralis and semitendinosus firing frequency (26.9–35.4%). In both ages leg stiffness decreased (9.2–10.2%) and reactive strength increased pre to post simulated match (U16 8.0%; U17 2.5%). A comparison of changes between age groups did not show any differences. This study demonstrates a decrease in neuromuscular performance post simulated match play in both ages but observed changes were not age dependent.

The cumulative and residual changes in eccentric knee flexor strength indices following soccer-specific treadmill running: Novel considerations of angle specific torque

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.

Influence of competition on performance factors in under-19 soccer players at national league level

The aim of this study was to analyse and quantify the acute effects of competition on several performance factors in under-19 male soccer players. To this end, 198 national league players (17.56 ± 0.78 years) performed various tests to measure jump capacity, kicking velocity and sprint times immediately pre-match (T1), at half-time (T2) and post-match (T3). Tests included kicking the ball to measure ball velocity (KICK), sprinting for 40 meters, timing the first 30 meters (30mACCEL), the last 10 meters (10mACCEL) and the total distance (40mACCEL), and performing countermovement jumps (CMJ). For subsequent analysis, the sample was divided into 5 playing positions: goalkeepers (n = 24), defenders (n = 51), midfielders (n = 36), wingers (n = 54) and forwards (n = 33). For all positions, we found a significant decline in performance (p<0.05) for kicking velocity (2.91% - 6.51%) and sprinting (0.44%-5.85%). For the CMJ, all positions except defenders presented a significant decline in performance that ranged from 1.5% to 4.56%. These findings highlight the need to individualise fitness training, taking into account the match needs and demands of the different playing positions in order to minimise the effects of match fatigue and accelerate post-match recovery.

The acute effect of match-play on hip range of motion and isometric strength in elite tennis players

Background

Groin injuries are some of the most common injuries tennis players suffer. Several factors (e.g., post-match decrease in hip adductor (ADD) strength) have been proposed as possible mechanisms for increasing the incidence of this type of injury. However, the risk factors of developing groin injuries after a tennis match have not yet been delineated.

Objective

The aim of this study was to determine the effect of tennis match-play on isometric ADD and abductor (ABD) strength and passive hip range of motion (ROM).

Methods

Twenty-six male tennis players (20.30 ± 4.98 years) took part in this study. Participants completed an evaluation of strength and flexibility hip measurements before and after a simulated tennis match. Dominant and non-dominant passive hip ROM, ADD and ABD isometric strength, and the ADD/ABD strength ratio were measured before and immediately post-match. A global positioning system (GPS) and a session rating of perceived exertion (RPE) were used to assess the locomotive demands and internal match load.

Results

Isometric dominant ADD strength (17.8%, p ≤ 0.01) and ADD/ABD strength ratio (11.6%, p = 0.04) were lower post-match compared to the pre-match values. No between-limbs differences were observed for isometric ADD strength, ABD strength, and passive hip ROM tests. RPE showed an expected increase between pre- vs. post-match (pre- vs. post-warming-up, 3.42 ± 2.08 vs. 5.62 ± 2.29, p < 0.01). In addition, a significant relationship between ADD strength and the volume of tennis practice per week was found, stablishing that tennis players with lower volume of training per week suffered a reduction in ADD strength in their dominant limb after match-play (r = 0.420, p = 0.04).

Conclusion

The assessment of ADD strength and the ADD/ABD strength ratio in the dominant limb may be considered a post-match tool that can be used to identify players who require rest and additional recovery strategies before competing again.

Effects of basketball match-play on ankle dorsiflexion range of motion and vertical jump performance in semi-professional players

BACKGROUND

The aim of this study was to investigate the effects of basketball match-play on ankle dorsiflexion range of motion (ROM) and countermovement (CMJ) performance, and their association with internal match load.

METHODS

Thirty semi-professional basketball players participated in this study. Ankle dorsiflexion ROM and bilateral CMJ performance were evaluated before (pre-match) and immediately after match-play (post-match). In addition, ankle dorsiflexion ROM was measured 48 hours post-match. Furthermore, for each player, the ankle dorsiflexion ROM scores were categorized as normal or restricted according to previously reported reference values (>2 cm change from baseline pre-match to post-match and to 48 hours post-match).

RESULTS

Ankle dorsiflexion ROM was increased post-match from pre-match in dominant and non-dominant limbs (most likely small) and decreased 48 hours post-match (most likely moderate) compared with immediately post-match measures in both limbs. Approximately 20% of all players showed restricted ankle dorsiflexion ROM values 48 hours post-match. CMJ performance was higher post-match than pre-match.

CONCLUSIONS

Ankle dorsiflexion ROM is still reduced 48 h after a competitive basketball match in semi-professional basketball players. The implementation of specific recovery strategies aiming at minimizing a decrease in ankle dorsiflexion after a match might be considered to reduce the likelihood of ankle injury.

Isometric Posterior Chain Peak Force Recovery Response Following Match-Play in Elite Youth Soccer Players: Associations with Relative Posterior Chain Strength

The purpose of this study was to determine changes in two tests of lower limb isometric posterior chain force (IPC-F) following 90 min of match-play in elite youth soccer players and the interaction between relative strength and recovery profile. 14 players (age: 16 ± 2 years) performed 3 × 3 second IPC-F tests unilaterally at 30° and 90° of knee and hip flexion pre- and post-match, +24 h, +48 h, and +72 h post-match. Peak force was recorded for both limbs, combined and expressed relative to bodyweight (N/kg). A two-way repeated measures analysis of variance was performed to determine differences in force output between joint angles, time intervals and subjects. As there was no interaction between angle and time (p = 0.260), we report the change between timepoints as mean ∆ in 90° + 30° IPC-F. Relative to pre-match IPC-F, there were significant decreases post (∆ = −18%; p > 0.001) and at +24 h (∆ = −8%; p = 0.040), no significant difference at +48 h (∆ = 0%; p = 0.992) and a significant increase at +72 h (∆ = +12%; p = 0.005). There was a large inter-individual variability in recovery profile at both angles and substantial differences between post-match deficits at 90° (−10.8%) compared to 30° (−20.7%). Higher pre-match IPC-F was correlated with the magnitude of IPC-F deficits at both angles and all time points (r = 0.56 to 0.70, p = < 0.01) except for post-match 90°. Regular IPC-F monitoring to determine the magnitude of match-induced fatigue and track recovery may help inform decision-making regarding modifications to individual players training load, particularly as there is a large inter-individual variability in response to competition. Further research is warranted to better understand and address the finding that stronger players showed larger force deficits and slower recovery following match-play.

Acute effects of a single tennis match on passive shoulder rotation range of motion, isometric strength and serve speed in professional tennis players

Shoulder pain has been associated with glenohumeral internal rotation deficit (GIRD) and a reduction in external rotation (ER) strength; however, in tennis players, there is scarce evidence regarding the impact of a single match on shoulder range of motion (ROM), strength and serve speed. The aim of this study was to determine the acute effect of a single tennis match on shoulder rotation ROM, isometric strength and serve speed. Twenty-six professional tennis players participated in the study (20.4±4.4 years; 10.5±3.2 years tennis expertise; 20.5±5.4 h/week training). Passive shoulder external (ER-ROM) and internal rotation ROM (IR-ROM), ER and IR isometric strength were measured before and after a single tennis match (80.3±21.3 min) in both shoulder´s. Moreover, the total arc of motion (TAM) and ER/IR strength ratio were calculated. Video analysis was used to assess the number of serves and groundstrokes, while a radar gun was utilized to measure maximal ball speed. In the dominant shoulder, compared to pre-match levels, IR-ROM was significantly reduced (-1.3%; p = 0.042), while ER-ROM (5.3%; p = 0.037) and TAM (3.1%; p = 0.050) were significantly increased. In the non-dominant shoulder, ER-ROM (3.7%; p = 0.006) was increased. Furthermore, in the dominant shoulder, the isometric ER strength was significantly reduced after the match (-4.8%; p = 0.012), whereas serve speed was not significantly reduced after match (-1.16%; p = 0.197). A single tennis match leads to significant reductions in shoulder ROM (e.g., IR of the dominant shoulder) and isometric strength (e.g., ER of the dominant shoulder). This study reveals the importance of recovery strategies prescription aiming at minimize post-match alteration in the shoulders.

The Individual and Combined Effects of Multiple Factors on the Risk of Soft Tissue Non-contact Injuries in Elite Team Sport Athletes

Aim: Relationships between athlete monitoring-derived variables and injury risk have been investigated predominantly in isolation. The aim of this study was to evaluate the individual and combined effects of multiple factors on the risk of soft-tissue non-contact injuries in elite team sport athletes. Methods: Fifty-five elite Australian footballers were prospectively monitored over two consecutive seasons. Internal and external training load was quantified using the session rating of perceived exertion and GPS/accelerometry, respectively. Cumulative load and acute-to-chronic workload ratios were derived using rolling averages and exponentially weighted moving averages. History of injuries in the current and previous seasons was recorded along with professional experience, weekly musculoskeletal screening, and subjective wellness scores for individual athletes. Individual and combined effects of these variables on injury risk were evaluated with generalized linear mixed models. Results: High cumulative loads and acute-to-chronic workload ratios were associated with increased risk of injuries. The effects for measures derived using exponentially weighted moving averages were greater than those for rolling averages. History of a recent injury, long-term experience at professional level, and substantial reductions in a selection of musculoskeletal screening and subjective wellness scores were associated with increased risk. The effects of high cumulative loads were underestimated by ~20% before adjusting for previous injuries, whereas the effects of high acute-to-chronic workload ratios were overestimated by 10-15%. Injury-prone players, identified via player identity in the mixed model, were at > 5 times higher risk of injuries compared to robust players (hazard ratio 5.4, 90% confidence limits 3.6-12) despite adjusting for training load and previous injuries. Combinations of multiple risk factors were associated with extremely large increases in risk; for example, a hazard ratio of 22 (9.7-52) was observed for the combination of high acute load, recent history of a leg injury, and a substantial reduction in the adductor squeeze test score. Conclusion: On the basis of our findings with an elite team of Australian footballers, the information from athlete monitoring practices in team sports should be interpreted collectively and used as a part of the injury prevention decision-making process along with consideration of individual differences in risk.

Time to get our four priorities right: an 8-year prospective investigation of 1326 player-seasons to identify the frequency, nature, and burden of time-loss injuries in elite Gaelic football

Managing injury risk requires an understanding of how and when athletes sustain certain injuries. Such information guides organisations in establishing evidence-based priorities and expectations for managing injury risk. In order to minimise the impact of sports injuries, attention should be directed towards injuries that occur frequently, induce substantial time-loss, and elevate future risk. Thus, the current study aimed to investigate the rate at which elite Gaelic football players sustain different time-loss injuries during match-play and training activities. Datasets (n = 38) from elite Gaelic football teams (n = 17) were received by the National Gaelic Athletic Association Injury Surveillance Database from 2008 to 2016. A total of 1,614 time-loss injuries were analysed. Each season teams sustained 24.0 (interquartile ranges) (IQR 16.0–32.0) and 15.0 (IQR 10.0–19.0) match-play and training injuries, respectively. When exposure was standardised to 1,000 h, greater rates of injury (12.9, 95% CI [11.7–14.3]) and time-loss days (13.4, 95% CI [12.3–14.9]) were sustained in match-play than in training. Acute injury rates were 3.1-times (95% CI [2.7–3.4]) greater than chronic/overuse injuries. Similarly, non-contact injury rates were 2.8-times (95% CI [2.5–3.2]) greater than contact injuries. A total of 71% of injuries in elite Gaelic football affected five lower limb sites. Four lower limb-related clinical entities accounted for 40% of all time-loss injuries (hamstring, 23%; ankle sprain, 7%; adductor-related, 6%; quadriceps strain, 5%). Thus, most risk management and rehabilitation strategies need to be centred around five lower limb sites—and just four clinical entities. Beyond these, it may be highly unlikely that reductions in injury susceptibility can be attributed to specific team interventions. Thus, compliance with national databases is necessary to monitor injury-related metrics and future endeavours to minimise injury risk.

Knee flexion not hip extension strength is persistently reduced following hamstring strain injury in Australian Football athletes: Implications for Periodic Health Examinations

OBJECTIVES

Determine whether clinically feasible tests of isometric lower limb strength and range of motion (ROM) in Australian Football (AF) athletes are useful in Periodic Health Examinations to identify persistent deficits following hamstring strain injury (HSI).

DESIGN

Case-control.

METHODS

Thirty-seven male, semi-professional AF athletes (mean±SD; age, 20.2±2.9years; height, 1.7±0.5m; mass, 81±9.2kg) participated, ten athletes (37%) reported HSI within the previous three seasons of competition. Comparisons of pre-season isometric knee flexion and hip extension strength variables (peak force, torque and torque normalised to body mass) and hip, knee and ankle ROM measures were made between athletes with and without past-history of HSI using linear mixed-effect models. A logistic regression evaluated whether any of the outcome measures could differentiate athletes with a past-history of HSI.

RESULTS

Knee flexion peak force, torque and torque normalised to body mass were significantly reduced in athletes with a past-history of HSI (coefficient, 95% CI) (-44.8N, -86.3 to -3.3), (-22.2Nm, -40.5 to -3.7) and (-0.2Nmkg^-1, -0.4 to 0.0) respectively. Knee flexion peak torque normalised to body mass (Nmkg^-1) approached significance as a test was able to differentiate athletes with history of HSI (p=0.068). There were no differences between groups for any hip extension strength or lower limb ROM outcome measures.

CONCLUSIONS

Deficits in isometric peak knee flexion strength persist for up to three seasons following HSI in AF athletes. Isometric knee flexion strength testing may be a clinically feasible option for Periodic Health Examinations and inform tertiary injury prevention strategies.

Normal Variability of Weekly Musculoskeletal Screening Scores and the Influence of Training Load across an Australian Football League Season

Aim: The sit and reach test (S&R), dorsiflexion lunge test (DLT), and adductor squeeze test (AST) are commonly used in weekly musculoskeletal screening for athlete monitoring and injury prevention purposes. The aim of this study was to determine the normal week to week variability of the test scores, individual differences in variability, and the effects of training load on the scores. Methods: Forty-four elite Australian rules footballers from one club completed the weekly screening tests on day 2 or 3 post-main training (pre-season) or post-match (in-season) over a 10 month season. Ratings of perceived exertion and session duration for all training sessions were used to derive various measures of training load via both simple summations and exponentially weighted moving averages. Data were analyzed via linear and quadratic mixed modeling and interpreted using magnitude-based inference. Results: Substantial small to moderate variability was found for the tests at both season phases; for example over the in-season, the normal variability ±90% confidence limits were as follows: S&R ±1.01 cm, ±0.12; DLT ±0.48 cm, ±0.06; AST ±7.4%, ±0.6%. Small individual differences in variability existed for the S&R and AST (factor standard deviations between 1.31 and 1.66). All measures of training load had trivial effects on the screening scores. Conclusion: A change in a test score larger than the normal variability is required to be considered a true change. Athlete monitoring and flagging systems need to account for the individual differences in variability. The tests are not sensitive to internal training load when conducted 2 or 3 days post-training or post-match, and the scores should be interpreted cautiously when used as measures of recovery.

Effects of the Nordic Hamstring exercise on sprint capacity in male football players: a randomized controlled trial

This assessor-blinded, randomized controlled superiority trial investigated the efficacy of the 10-week Nordic Hamstring exercise (NHE) protocol on sprint performance in football players. Thirty-five amateur male players (age: 17-26 years) were randomized to a do-as-usual control group (CG; n = 17) or to 10-weeks of supervised strength training using the NHE in-season (IG; n = 18). A repeated-sprint test, consisting of 4 × 6 10 m sprints, with 15 s recovery period between sprints and 180 s between sets, was conducted to evaluate total sprint time as the primary outcome. Secondary outcomes were best 10 m sprint time (10mST) and sprint time during the last sprint (L10mST). Additionally, peak eccentric hamstring strength (ECC-P_HS) and eccentric hamstring strength capacity (ECC-CAP_HS) were measured during the NHE. Ten players were lost to follow-up, thus 25 players were analyzed (CG n = 14; IG n = 11). Between-group differences in mean changes were observed in favor of the IG for sprint performance outcomes; TST (-0.649 s, p = 0.056, d = 0.38), 10mST (-0.047 s, p = 0.005, d = 0.64) and L10mST (-0.052 s, p = 0.094, d = 0.59), and for strength outcomes; ECC-P_HS (62.3 N, p = 0.006, d = 0.92), and ECC-CAP_HS (951 N, p = 0.005, d = 0.95). In conclusion, the NHE showed small-to-medium improvements in sprint performance and large increases in peak eccentric hamstring strength and capacity.

TRIAL REGISTRATION NUMBER

NCT02674919.

Isokinetic strength assessment offers limited predictive validity for detecting risk of future hamstring strain in sport: a systematic review and meta-analysis

Objective

To examine the value of isokinetic strength assessment for predicting risk of hamstring strain injury, and to direct future research into hamstring strain injuries.

Design

Systematic review.

Data sources

Database searches for Medline, CINAHL, Embase, AMED, AUSPORT, SPORTDiscus, PEDro and Cochrane Library from inception to April 2017. Manual reference checks, ahead-of-press and citation tracking.

Eligibility criteria for selecting studies

Prospective studies evaluating isokinetic hamstrings, quadriceps and hip extensor strength testing as a risk factor for occurrence of hamstring muscle strain.

Methods

Independent search result screening. Risk of bias assessment by independent reviewers using Quality in Prognosis Studies tool. Best evidence synthesis and meta-analyses of standardised mean difference (SMD).

Results

Twelve studies were included, capturing 508 hamstring strain injuries in 2912 athletes. Isokinetic knee flexor, knee extensor and hip extensor outputs were examined at angular velocities ranging 30–300°/s, concentric or eccentric, and relative (Nm/kg) or absolute (Nm) measures. Strength ratios ranged between 30°/s and 300°/s. Meta-analyses revealed a small, significant predictive effect for absolute (SMD=−0.16, P=0.04, 95% CI −0.31 to −0.01) and relative (SMD=−0.17, P=0.03, 95% CI −0.33 to −0.014) eccentric knee flexor strength (60°/s). No other testing speed or strength ratio showed statistical association. Best evidence synthesis found over half of all variables had moderate or strong evidence for no association with future hamstring injury.

Summary/Conclusion

Despite an isolated finding for eccentric knee flexor strength at slow speeds, the role and application of isokinetic assessment for predicting hamstring strain risk should be reconsidered, particularly given costs and specialised training required.

Monitoring the effect of football match congestion on hamstring strength and lower limb flexibility: Potential for secondary injury prevention?

OBJECTIVES

To investigate the effect of competitive football match congestion on hamstring strength and lower limb flexibility.

DESIGN

Repeated measures.

SETTING

Elite male youth football.

PARTICIPANTS

Fifteen male elite youth football players from the national football association centre of excellence were included (age = 15.81 ±0.65 years, height = 171.95 ±6.89 cm, weight = 65.93 ±7.53 kg).

MAIN OUTCOME MEASURES

Hamstring strength and pain, ankle dorsiflexion, hip extension, knee extension and flexion range of motion.

RESULTS

Hamstring strength was highest at baseline and significantly reduced at 24 (p = 0.001, mean difference -0.19 Nm/Kg, CI₉₅ -0.28, -0.1) and 48 h post-match 1 (p = 0.002, mean difference -0.16 Nm/Kg, CI₉₅ -0.25, -0.07). Strength recovered by match day 2 before significantly reducing again 24 h post-match 2 (p = 0.012, mean difference -0.17 Nm/Kg, CI₉₅ -0.29, -0.04). Pain was lowest at baseline and increased in the post-match periods (p < 0.05) with standardised effect sizes ranging from 0.07 to 0.42. Passive knee flexion range decreased post-match (p < 0.01) with mean differences of 1.5°-2.7°. The other flexibility measures remained unaffected by match play.

CONCLUSION

Isometric hamstring strength and pain can be considered for inclusion in-season to monitor player's post-match hamstring recovery characteristics during congested match fixtures.