Purpose: Specialisation in youth football is common, often with the goal of heightened sporting success later in life. The purpose of this study was to investigate if sprint and change of direction (COD) performance differs between specialised and diversified youth football players. Methods: Twenty male football players (age: 15.9 ±1.1 years), grouped as specialised (n=11) or diversified (n=9), were compared in 30m sprint and 5-0-5 COD tasks. In the sprint, 10m and 30m completion time and force-velocity profiles were examined. COD performance was assessed using total time, COD deficit, and 2-dimensional video to determine if participants used backward trunk inclination and heel strike during their penultimate foot contact. Linear mixed models and Chi-square analyses were used to compare groups with significance set at p ≤0.05. Results: Sprint and COD performance did not differ between groups (p >0.05). Significantly greater COD asymmetries were seen in the specialised group (9%) compared to the diversified group (4%). While not significantly different, effect sizes suggest potential differences in task completion strategy were observed based on force-velocity profiles during sprints. Conclusions: These results suggest a specialised pathway does not lead to improved performance in sprint or COD in youth football players, but it may lead to differences in the strategy used to perform these tasks.

PURPOSE:The aim of this study was to investigate the longitudinal associations between peak force (PF) in the isometric start position pull (ISPP), isometric transition position pull (ITPP), and isometric mid-thigh pull (IMTP) with weightlifting performance. METHODS:A retrospective longitudinal analysis was conducted using isometric assessment and performance data collected over a period of up to 3 years from 7 international-level female weightlifters (age 26.8 [7.4] y; body mass 59.9 [7.0] kg). The dependent variables were absolute (Total) and allometrically scaled competition performance (Totala). The independent variables were absolute (ISPP, ITPP, IMTP) and allometrically scaled (ISPPa, ITPPa, IMTPa) PF in the 3 pull positions and Time (3-mo intervals). Separate linear mixed models were used to examine their longitudinal associations. RESULTS:The ISPP and ISPPa showed significant positive associations with Total and Totala (P < .01), explaining 31% and 12% of the variance. Time as a fixed factor was not significant (P > .05), and reduced models (omitting Time) explained greater variance of 45% and 18%, respectively. The ITPP, IMTP, ITPPa and IMTPa were not significant in full models, yet reduced models identified these as significant predictors (P < .05) but with poorer model fit. CONCLUSIONS:The ISPP demonstrates the strongest and most stable longitudinal predictor of weightlifting performance, supporting its use as a primary assessment for monitoring performance changes.

Despite passing a battery of tests and being considered ready to return to sport, residual deficits in physical capacity of the lower limb are commonly present in multidirectional athletes following an anterior cruciate ligament (ACL) reconstruction. These can have a detrimental impact on individual and overall team athletic performance and may increase the risk of reinjury. Targeted strategies to assess and restore lower limb performance within rehabilitation are therefore crucial. The aim of this review was to (a) describe common residual deficits in physical capacities after ACL reconstruction, (b) highlight achievable performance metrics to target during rehabilitation to assist practitioners in collecting useful information, and (c) propose examples of evidence-based strategies to restore full recovery.

Strength and conditioning provision for young athletes offers unique challenges for coaches. For example, periods of rapid and non-uniform growth in skeletal structures are common, resulting in temporary reductions in performance and heightened injury risk. This chapter first identifies pertinent risk factors for prevalent injuries experienced in this cohort and multifactorial components that must be considered when assessing an athlete’s risk profile. After this, the chapter reviews and critically analyses the effectiveness of current injury prevention programmes administered to youth athletes, specifically relating to improvements in function and reductions in injury incidence. Finally, practical tools and applied examples are provided to aid in the design of effective training programmes, concluding with a hierarchical injury risk factor training model, which systematically integrates risk factor screening with the development of individualised programmes that target deficits in neuromuscular control.

BACKGROUND:The aim of this study is to examine relative five-repetition maximum (RM) box squat, rear-foot elevated split squat (RFESS), leg extension strength and vertical jump scores in amateur athletes who have returned to sport following anterior cruciate ligament (ACL) reconstruction. METHODS:Overall, 53 amateur athletes completed a strength and vertical jump assessment including 5RM box squat, RFESS, Leg Extension, countermovement jump (CMJ), single leg (SL) CMJ and SL drop jump (DJ). RESULTS:Relative 5RM values of 1.16, 0.6 and 0.65 were found for box squat, RFESS and leg extension respectively. Significant main effects of limb were observed across most outcomes, with the ACL-reconstructed limb showing lower strength and jump performance. Males outperformed females on all strength and jump metrics. A main effect of graft type was found for leg extension strength, but post-hoc comparisons were not significant. Time from surgery did not moderate the effects of limb, gender, or graft type, except for one interaction with eccentric deceleration impulse. CONCLUSIONS:Single joint strength and vertical jump scores were lower in the ACL reconstructed limb in comparison to the uninvolved limb, whereas no differences were found in RFESS. Females showed lower relative scores in all tests, whereas no difference was found according to graft type. Time from surgery did not moderate the effects of limb, gender and graft type on strength and vertical jump scores, except for SLCMJ eccentric deceleration impulse.

Maestroni, L, Turner, A, Rosalia, A, Algeri, C, Moioli, F, Guastella, M, Civera, F, Midali, C, Bettariga, F, and Read, P. How do multi- and single-joint strength levels relate to vertical jump performance and biomechanics in amateur athletes returned to sport after anterior cruciate ligament reconstruction? J Strength Cond Res 40(1): 39–47, 2026—Understanding the relationship between multijoint and single-joint strength and vertical jumps performance, stretch-shortening cycle (SSC) function, and phase-specific impulses in athletes after anterior cruciate ligament (ACL) reconstruction is necessary to optimize rehabilitation strategies by identifying the hierarchy of physical qualities that underpin complete recovery after ACL reconstruction. Fifty-four amateur athletes completed a strength and vertical jump assessment. Relative 5RM box squat, rear-foot elevated split squat (RFESS), and leg extension explained between 25.2 and 56.9% of the variance in countermovement jump (CMJ) height, single-leg (SL) CMJ height, reactive strength index modified (RSImod), and SL drop jump (DJ) height and reactive strength index (RSI). Relative 5RM box squat and RFESS were consistent predictors. Relative 5RM RFESS and leg extension strength explained between 22.1 to 31% and 17 to 47.2% of the variance in CMJ and SLCMJ concentric and eccentric deceleration impulses, respectively. Leg extension was a significant independent predictor for most phase-specific impulse variables. The logistic regression analysis did not show any predicting ability of both 5RM RFESS and leg extension scores in identifying SSC function. A stronger association with CMJ, SLCMJ, and SLDJ performance was found for relative 5RM box squat and RFESS. 5RM leg extension was a significant predictor in explaining part of the variance in CMJ and SLCMJ concentric and eccentric deceleration impulses. Impaired SSC efficiency was present, but not predicted by strength scores. Our findings underscore the importance of both multi- and single-joint strength in explaining jump performance and phase-specific impulses, while indicating that SSC efficiency is influenced by additional neuromuscular factors beyond strength alone.

Large interindividual differences can exist in the timing and tempo of growth and maturation of youth athletes. This can provide significant physical performance advantages to young athletes who mature in advance of their peers. The aim of this systematic review was to determine the magnitude of differences in sprinting and jumping performance in youth of different maturity status (classified as pre-, circa- or post-peak height velocity [PHV]) (aged < 18 years) to enhance the evaluation of performance. Eligibility criteria for inclusion were as follows: (1) the study had cross-sectional data available; (2) participants were male and/or female ≤ 18 years of age; (3) a somatic measure of maturity was used to identify maturity status (e.g. Mirwald or Khamis-Roche methods) with at least two maturity status classifications present; (4) the study included a measurement of sprinting speed (e.g. 10–100-m sprint data) and/or jump tests commonly used to assess power (e.g. countermovement jump [CMJ]). Searches were conducted up to November 2024 in PubMed, Embase, SPORTDiscus and preprint servers SportRxiv and medRxiv to identify any unpublished trials. Risk of bias and study quality was assessed using the Appraisal tool for Cross‐Sectional Studies (AXIS). Meta-analysis was computed using a random-effects model. The search identified 1578 studies. From those, 40 studies were identified for qualitative assessment and quantitative synthesis. In the primary analysis, 21 studies provided data for measures of speed, and 19 studies provided data for measures of power using jump tests. Sprinting and jumping performance increased with advancing maturity status and overall effect sizes were predominantly moderate to large between maturity groups. Pre-PHV versus post-PHV comparisons found moderate to large overall effect sizes (ES) for sprinting performance (10-m ES 1.34 [95

ABSTRACT:Maestroni, L, Turner, A, Read, P, Bettariga, F, Fenu, G, Rosalia, A, Guastella, M, and Bishop, C. Inter-limb asymmetry data in athletes with anterior cruciate ligament reconstruction: A comparison of different equations to interpret between-limb difference data. J Strength Cond Res 40(2): 158-166, 2026-Between-limb performance and biomechanical differences (i.e., interlimb asymmetries) after anterior cruciate ligament (ACL) reconstruction are monitored and reported during rehabilitation and at the time of return to sport. However, different asymmetry equations can alter the magnitude and consistency of the asymmetry. Fifty-three amateur athletes (16 women; 37 men; 28.5 ± 6.7 years; 177.1 ± 6.5 cm; 75.3 ± 10.8 kg) at a median of 28.1 months post-ACL reconstruction completed a strength and vertical jump assessment including 5 repetition maximum (RM) box squat, rear foot elevated split squats, leg extension and countermovement jump (CMJ), single-leg CMJ, and single-leg drop jump. Large significant differences (ƞ 2 = 0.14-0.44) were found between unilateral equations for each variable assessed, and between bilateral equations (ƞ 2 = 0.17-0.34) for CMJ concentric and eccentric impulse asymmetries. Small to large significant pairwise differences were present between each equation and variable in unilateral tasks ( d = 0.46-2.30). For the CMJ, large significant pairwise differences were also found between most equations for CMJ concentric and eccentric impulse asymmetry ( d = 0.99-3.04). We recommend the use of the Standard Percentage Difference (with direction) formula for unilateral tasks and the Bilateral Asymmetry Index 1 for bilateral tasks.

During rehabilitation, the importance of restoring strength and power in a stage-based framework highlights the paramount role of testing and monitoring. Despite theoretical understanding of an optimal recovery pathway, it is unclear and inconsistent as to how practitioners implement force and power assessment following anterior cruciate ligament reconstruction (ACLR). We aimed to examine current worldwide practices with evaluating patients post-ACLR, identify the relative utilisation of different devices and methodologies across the rehabilitation process, and to explore the interactions between the implemented devices and respondents’ self-perceived testing quality (evaluated by participants via a Likert scale). Data were collected via an international online survey composed of 100 items, organised across 12 sections, exploring the demographics of respondents and implemented testing devices to assess individuals after ACLR and their perceived testing quality. A total of 1154 practitioners from 78 different countries completed the survey. According to the pre-defined eight categories, 157 different combinations were recorded among practitioners. Respondents tended to use multiple devices (95.8

ABSTRACT Upper-limb injuries are common among baseball pitchers, creating significant time loss for the player and financial loss for the team. Multiple studies have outlined the kinetics and kinematics of a baseball pitch, and many of which evaluate testing or training methods to enhance performance and reduce injury risk. However, a systematic approach that integrates testing and training to optimize health and performance in baseball pitchers has not been presented. The aims of this article are threefold: (a) analyze the sport demands to identify the key biomechanical requirements and injury epidemiology; (b) present a test battery to examine the components identified in the needs analysis; and (c) develop a progressive sequence of exercises related to each of the assessments performed, which can then be used to formulate an athletic training program.

Background: Deceleration is a fundamental component of multidirectional speed by which athletes reduce the velocity of their centre of mass to stop or execute changes of direction following acceleration or running at a constant velocity. Enhancing deceleration abilities is crucial for athletes as successfully executing horizontal deceleration has important implications for match outcomes in sports requiring rapid multidirectional movements. However, specific training interventions targeting deceleration are scarce. The purpose of this systematic review and meta-analysis was to examine the effects of training interventions on deceleration performance in adult team-based field and court sports athletes. Methods: A systematic literature search was conducted through electronic databases, SPORTdiscus, PubMed, and Web of Science from inception to February 2022, and re-run in May 2023. The search terms were related to different training interventions and kinetic, kinematic, and performance outcomes related to deceleration performance. Studies were included if they consisted of a randomised controlled trial which investigated the effects of training on deceleration-specific outcome measures in adult team-based field and court sports athletes. Risk of bias was assessed using the revised Cochrane risk-of-bias tool for randomised trials (RoB2). Post-intervention effect sizes (Hedge’s g) were calculated between the intervention and control groups and a meta-analysis was performed using a random effects model. Results: Twelve studies were included, with 29 deceleration-specific outcomes measured in a total of 381 participants. There was inconsistency in methodological designs, including control group types, length and type of interventions and in reported deceleration-specific outcome measures. Across all observations of deceleration performance measures there was a standardised mean difference of -0.04 (95% CI: -0.50, 0.42), favouring control groups, indicating little effect of training on deceleration performance. For secondary outcomes related to deceleration, for kinetics (SMD = -0.29, 95% CI = -0.83, 0.25, I2 = 55%, p < 0.01), joint kinetics (SMD = -0.20, 95% CI = -1.01, 0.61, I2 = 68%, p < 0.01) and muscle activation (SMD = -0.10, 95% CI = -0.44, 0.24, I2 = 19%, p = 0.28) had greater effects for control groups, whereas joint kinematics (SMD = 0.07, 95% CI = -0.11, 0.24, I2 = 0%, p = 0.77), favoured the intervention groups. Conclusion: For the deceleration-specific outcomes reported in the included studies, training was not likely to produce a performance improvement in participants compared to control groups. However, due to methodological inconsistencies between studies and observed high risk of bias, the results should be interpreted with caution. More rigorous research methods should be included in the future to address areas that may introduce potential biases. Future research should address the differences in the type, timing, frequency, and duration of the implemented training interventions for improving deceleration performance, and in the reported deceleration-specific outcome measures. Registration: This systematic review was registered on the Open Science Framework (https://osf.io/cmwbr) (https://doi.org/10.17605/OSF.IO/CMWBR)

Purpose: This study examined the physical determinants of 60-m sprint and long jump (LJ) performance and differences between maturity groups in physical characteristics in young male track-and-field athletes. Methods: Competition results, countermovement jump, isometric leg press, 10-5 repeated jump test, and 50-m sprint were collected over 3 seasons for 54 male athletes (age 13 [1] y; stature 160.0 [8.9] cm; body mass, 48.0 [9.8] kg; percentage predicted adult height 92.2% [5.5%]) grouped by maturity status: approaching- (n = 16), circa- (n = 19), and post-peak height velocity (PHV) (n = 19). Results: There were significant between-group differences in 60 m, LJ, and all physical testing variables (P < .001, g = 0.88-5.44) when comparing the approaching- and circa-PHV groups with the post-PHV group. Significant differences were identified between the approaching and circa-PHV groups in 40-m (P = .033, g = 0.89), 50-m (P = .024, g = 1.64), and 60-m (P < .001, g = 0.89) sprint times. Countermovement jump and 50-m sprint variables were consistently important for projection of 60 m and LJ performance across the valid multivariate models. Conclusions: Large differences in performance across maturity groups highlight the importance of understanding athletes' maturity status to accurately interpret performance. Several physical performance variables were important for projecting competition 60 m and LJ performance.

Background: There is no consensus on the optimal testing procedure to determine return-to-sport (RTS) readiness after anterior cruciate ligament (ACL) reconstruction. Current approaches use limb symmetry across a range of tests, but this does not consider a patient’s level of athleticism or benchmarks relative to his or her noninjured counterparts. Purpose: To examine the utility of the Total Score of Athleticism (TSA), a composite scale including strength, power, and reactive strength assessments, to aid RTS decision-making. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 95 professional soccer players (60 who underwent ACL reconstruction [mean age, 25.1 ± 12.6 years] and 35 who were uninjured [mean age, 23.8 ± 2.8 years]) completed a battery of tests including isokinetic knee extension and flexion torque, bilateral and unilateral countermovement jump height, relative peak power, and reactive strength index–modified. The TSA score (derived from Z scores) was calculated, and we (1) examined differences between the ACL-reconstructed and uninjured groups at the time of RTS, (2) assessed the predictive ability of the TSA to identify the player’s status (ACL reconstruction vs uninjured control), and (3) included a case series to discuss the characteristics of players who sustained a subsequent injury within 4 months after RTS. Results: A large difference between the ACL-reconstructed and uninjured groups in the TSA score ( d = 0.84; P < .0001) was evident. For every additional increase of 1 unit in the TSA score, the odds of belonging to the ACL-reconstructed group decreased by 74% (95% CI, 0.19-0.56). By visual inspection, the frequency of reinjured players was higher in the low (4/7) TSA tertile compared with the medium (2/7) and high (1/7) TSA tertiles. Conclusion: Preliminary evidence indicates that the TSA may be a useful RTS readiness tool, as the composite score derived from strength and power measures was different in soccer players at the time of RTS after ACL reconstruction compared with healthy matched controls. There was also a higher frequency of low TSA scores in players who sustained a second injury after RTS. Therefore, it is recommended to routinely administer RTS tests encompassing strength, power, and reactive strength qualities each season across the largest possible number of players (ideally teammates).

To assess the mechanisms of ACL injury in male professional football players in Qatar across multiple seasons using systematic video analysis. 15 ACL injuries occurred in competition among the professional football teams that participated in an injury Surveillance Programme during 6 seasons (2013/2014 to 2018/2019). High-definition broadcast videos of these injuries were analyzed (49 views; 34 slow motion) by five analysts who independently described the injury mechanisms (situation, behavior, biomechanical characteristics) using validated observational tools. A knee valgus mechanism was observed in two-thirds of the cases (1 with direct contact to the knee, 3 with indirect contact (other body parts) and 6 with no contact). No visible valgus was reported in 2 of the direct knee contact injuries, while 3 cases of non-contact and indirect contact injuries were unclear. We observed 4 main categories of injury situation among those (n = 12) classified as non-contact/ indirect contact (multiple combinations were possible): pressing (n = 6), tackling or being tackled (n = 4), blocking (n = 3) and screening (n = 2). Direct contact injuries (n = 3) were suffered by 2 players during tackling and 1 whilst being tackled. Contact injuries represented only 20% of ACL injuries occurring during competition in Qatari professional soccer players. Independent of the playing situation, knee valgus was frequently observed (10/15 cases). Pressing was the most common situation (6/15 cases) leading to injury. Landing after heading was not reported in any of these ACL injuries.

Muscle injury classification systems for hamstring injuries have evolved to use anatomy and imaging information to aid management and prognosis. However, classification systems lack reliability and validity data and are not specific to individual hamstring muscles, potentially missing parameters vital for sport-specific and activity-specific decision making. A narrative evidence review was conducted followed by a modified Delphi study to build an international consensus on best-practice decision-making for the classification of hamstring injuries. This comprised a digital information gathering survey to a cohort of 46 international hamstring experts (sports medicine physicians, physiotherapists, surgeons, trainers and sports scientists) who were also invited to a face-to-face consensus group meeting in London . Fifteen of these expert clinicians attended to synthesise and refine statements around the management of hamstring injury. A second digital survey was sent to a wider group of 112 international experts. Acceptance was set at 70% agreement. Rounds 1 and 2 survey response rates were 35/46 (76%) and 99/112 (88.4%) of experts responding. Most commonly, experts used the British Athletics Muscle Injury Classification (BAMIC) (58%), Munich (12%) and Barcelona (6%) classification systems for hamstring injury. Issues identified to advance imaging classifications systems include: detailing individual hamstring muscles, establishing optimal use of imaging in diagnosis and classification, and testing the validity and reliability of classification systems. The most used hamstring injury classification system is the BAMIC. This consensus panel recommends hamstring injury classification systems evolve to integrate imaging and clinical parameters around: individual muscles, injury mechanism, sporting demand, functional criteria and patient-reported outcome measures. More research is needed on surgical referral and effectiveness criteria, and validity and reliability of classification systems to guide management.

Hamstring injuries (HSIs) are the most common athletic injury in running and pivoting sports, but despite large amounts of research, injury rates have not declined in the last 2 decades. HSI often recur and many areas are lacking evidence and guidance for optimal rehabilitation. This study aimed to develop an international expert consensus for the management of HSI. A modified Delphi methodology and consensus process was used with an international expert panel, involving two rounds of online questionnaires and an intermediate round involving a consensus meeting. The initial information gathering round questionnaire was sent to 46 international experts, which comprised open-ended questions covering decision-making domains in HSI. Thematic analysis of responses outlined key domains, which were evaluated by a smaller international subgroup (n=15), comprising clinical academic sports medicine physicians, physiotherapists and orthopaedic surgeons in a consensus meeting. After group discussion around each domain, a series of consensus statements were prepared, debated and refined. A round 2 questionnaire was sent to 112 international hamstring experts to vote on these statements and determine level of agreement. Consensus threshold was set a priori at 70%. Expert response rates were 35/46 (76%) (first round), 15/35 (attendees/invitees to meeting day) and 99/112 (88.2%) for final survey round. Statements on rehabilitation reaching consensus centred around: exercise selection and dosage (78.8%–96.3% agreement), impact of the kinetic chain (95%), criteria to progress exercise (73%–92.7%), running and sprinting (83%–100%) in rehabilitation and criteria for return to sport (RTS) (78.3%–98.3%). Benchmarks for flexibility (40%) and strength (66.1%) and adjuncts to rehabilitation (68.9%) did not reach agreement. This consensus panel recommends individualised rehabilitation based on the athlete, sporting demands, involved muscle(s) and injury type and severity (89.8%). Early-stage rehab should avoid high strain loads and rates. Loading is important but with less consensus on optimum progression and dosage. This panel recommends rehabilitation progress based on capacity and symptoms, with pain thresholds dependent on activity, except pain-free criteria supported for sprinting (85.5%). Experts focus on the demands and capacity required for match play when deciding the rehabilitation end goal and timing of RTS (89.8%). The expert panellists in this study followed evidence on aspects of rehabilitation after HSI, suggesting rehabilitation prescription should be individualised, but clarified areas where evidence was lacking. Additional research is required to determine the optimal load dose, timing and criteria for HSI rehabilitation and the monitoring and testing metrics to determine safe rapid progression in rehabilitation and safe RTS. Further research would benefit optimising: prescription of running and sprinting, the application of adjuncts in rehabilitation and treatment of kinetic chain HSI factors.

BACKGROUND:Strength and power is often reduced on the involved versus contralateral limb and healthy controls after anterior cruciate ligament (ACL) reconstruction, but no study has compared with preinjury values at the time of return to sport (RTS). HYPOTHESIS:Divergent recovery patterns in strength and power characteristics will be present at RTS relative to preinjury baseline data and healthy matched controls. STUDY DESIGN:Cohort study. LEVEL OF EVIDENCE:Level 3. METHODS:Isokinetic strength tests, bilateral and single-leg countermovement jumps (CMJ; SLCMJ) were measured before ACL rupture in 20 professional soccer players. These then had surgical reconstruction (ACL group) and completed follow-up testing before RTS. Healthy controls (uninjured group) were tested at the same time as the ACL group preinjury. Values recorded at RTS of the ACL group were compared with preinjury. We also compared the uninjured and ACL groups at baseline and RTS. RESULTS:Compared with preinjury, ACL normalized quadriceps peak torque of the involved limb (difference = -7%), SLCMJ height (difference = -12.08%), and Reactive Strength Index modified (RSImod) (difference = -5.04%) were reduced after ACL reconstruction. No significant reductions in CMJ height, RSImod, and relative peak power were indicated at RTS in the ACL group when compared with preinjury values, but deficits were present relative to controls. The uninvolved limb improved quadriceps (difference = 9.34%) and hamstring strength (difference = 7.36%) from preinjury to RTS. No significant differences from baseline were shown in SLCMJ height, power, and reactive strength of the uninvolved limb after ACL reconstruction. CONCLUSION:Strength and power in professional soccer players at RTS after ACL reconstruction were often reduced compared with preinjury values and matched healthy controls. CLINICAL RELEVANCE:Deficits were more apparent in the SLCMJ, suggesting that dynamic and multijoint unilateral force production is an important component of rehabilitation. Use of the uninvolved limb and normative data to determine recovery may not always be appropriate.

Context: Deficits in plyometric abilities are common after anterior cruciate ligament reconstruction (ACLR). Vertical re-bound tasks may provide a targeted evaluation of knee function.Objective: To examine the utility of a vertical hop test for assessing function after ACLR and establishing factors asso-ciated with performance.Design: Cross-sectional study.Setting: Rehabilitation program.Patients or Other Participants: Soccer players with a history of ACLR (n = 73) and matched control individuals (n = 195).Main Outcome Measure(s): The 10-second vertical hop test provided measures of jump height, the Reactive Strength Index (RSI), and asymmetry. We also examined possible predictors of hop performance, including single-legged vertical drop jump, isokinetic knee-extension strength, and the Interna-tional Knee Documentation Committee questionnaire score.Results: Between-limbs differences were identified only for the ACLR group, and asymmetry scores increased in those with a history of ACLR (P , .001) compared with the control group. The single-legged vertical drop jump, RSI, and knee-extension torque were significant predictors of 10-second hop height (R2 = 20.1%) and RSI (R2= 47.1%).Conclusions: Vertical hop deficits were present after ACLR, even after participants completed a comprehensive rehabilitation program. This may have been due to reduced knee-extension and reactive strength. Vertical hop tests warrant inclusion as part of the return-to-sport test battery.

Single leg drop jump (SLDJ) assessment is commonly used during the later stages of rehabilitation to identify residual deficits in reactive strength but the effects of physical capacity on kinetic and kinematic variables in male soccer players following ACL reconstruction remain unknown. Isokinetic knee extension strength, kinematics from an inertial measurement unit 3D system and SLDJ performance variables and mechanics derived from a force plate were measured in 64 professional soccer players (24.7 ± 3.4 years) prior to return to sport (RTS). SLDJ between-limb differences was measured (part 1) and players were divided into tertiles based on isokinetic knee extension strength (weak, moderate and strong) and reactive strength index (RSI) (low, medium and high) (part 2). Moderate to large significant differences between the ACL reconstructed and uninjured limb in SLDJ performance (d = 0.92-1.05), kinetic (d = 0.62-0.71) and kinematic variables (d = 0.56) were evident. Stronger athletes jumped higher (p = 0.002; d = 0.85), produced greater concentric (p = 0.001; d = 0.85) and eccentric power (p = 0.002; d = 0.84). Similar findings were present for RSI, but the effects were larger (d = 1.52-3.84). Weaker players, and in particular those who had lower RSI, displayed landing mechanics indicative of a 'stiff' knee movement strategy. SLDJ performance, kinetic and kinematic differences were identified between-limbs in soccer players at the end of their rehabilitation following ACL reconstruction. Players with lower knee extension strength and RSI displayed reduced performance and kinetic strategies associated with increased injury risk.

The key indications for surgical repair of hamstring injuries (HSIs) remain unclear in the literature due to a lack of high-level evidence and expert knowledge. The 2020 London International Hamstring Consensus meeting aimed to highlight clear surgical indications and to create a foundation for future research. A literature review was conducted followed by a modified Delphi process, with an international expert panel. Purposive sampling was used with two rounds of online questionnaires and an intermediate round involving a consensus meeting. The initial information gathering (round 1) questionnaire was sent to 46 international experts, which comprised open-ended questions covering decision-making domains in HSI. Thematic analysis of responses outlined key domains, which were evaluated by a smaller international subgroup (n=15) comprising clinical academic sports medicine physicians, physiotherapists and orthopaedic surgeons in a consensus meeting. After group discussion of each domain, a series of consensus statements were prepared, debated and refined. A round 2 questionnaire was sent to 112 international hamstring experts to vote on these statements and determine level of agreement. The consensus threshold was set a priori at 70% agreement. Rounds 1 and 2 survey respondents were 35/46 (76%) and 99/112 (88.4%), respectively. The consensus group agreed that the indications for operative intervention included: gapping at the zone of tendinous injury (87.2% agreement) and loss of tension (70.7%); symptomatic displaced bony avulsions (72.8%); and proximal free tendon injuries with functional compromise refractory to non-operative treatment (72.2%). Other important considerations for operative intervention included: the demands of the athlete/patient and the expected functional outcome (87.1%) based on the anatomy of the injury; the risk of functional loss/performance deficit with non-operative management (72.2%); and the capacity to restore anatomy and function (87.1%). Further research is needed to determine whether surgery can reduce the risk of reinjury as consensus was not reached within the whole group (48.2%) but was agreed by surgeons (70%) in the cohort. The consensus group did not support the use of corticosteroids or endoscopic surgery without further evidence. These guidelines will help standardise treatment of HSIs, specifically the indications and decision-making for surgical intervention.