BACKGROUND:The relationship between heat stress and injury risk in youth athletes is unknown. The purpose of the study was to identify the association between wet bulb globe temperature (WBGT) and injury risk in youth soccer athletes. HYPOTHESIS:Overall injury incidence would increase, and concussion incidence would decrease with higher WBGT. STUDY DESIGN:Prospective cohort study. LEVEL OF EVIDENCE:Level 2. METHODS:Injury characteristics were recorded by athletic trainers at Elite Clubs National League youth soccer events throughout the United States over 2 years, and WBGT was calculated for each day of each event. The associations of nontime-loss and time-loss injury and concussion incidence with WBGT were assessed through separate negative binomial regression models, adjusted for age and sex. RESULTS:A total of 1584 injuries and 306 concussions were reported from 42 events representing 315,113 player-hours. Injury incidence was 5.0 per 1000 player-hours overall and higher for girls than boys (5.6 vs 4.4 per 1000 player-hours respectively, incidence rate ratio [IRR], 1.38; 95% CI, 1.1-1.7; P ≤ 0.001). Concussion incidence was 0.97 per 1000 player-hours, and girls had a higher concussion incidence than boys (1.20 vs 0.78 per 1000 player hours; IRR, 1.39; 95% CI. 1.0-1.9; P = 0.03). Higher WBGT was associated with a lower incidence of injuries overall (IRR, 0.986; 95% CI, 0.98-0.99; P < 0.01), time-loss injuries (IRR, 0.983; 95% CI, 0.97-0.99; P < 0.01), and concussions (IRR, 0.981; 95% CI, 0.97-0.99; P = 0.01), but not nontime-loss injuries (IRR, 1.00; 95% CI, 0.99-0.99; P = 0.86). CONCLUSION:In this study of match injuries in youth soccer, we found that a higher WBGT was associated with a decreased incidence in overall injuries, as well as a lower incidence of concussions and time-loss injuries. Further research is warranted to understand the mechanisms behind these relationships, and whether they exist similarly in other athletic populations. CLINICAL RELEVANCE:These results help advance our understanding of environmental injury risk factors in youth soccer to inform decision making by support staff.
BACKGROUND:Neuromuscular training (NMT) improves biomechanical risk factors associated with anterior cruciate ligament (ACL) injury yet has failed to abate increasing ACL injury rates at scale. This study assessed sport-specific sensorimotor adaptations resulting from a NMT protocol with additive real-time sensorimotor augmented biofeedback (augmented NMT [aNMT] or sham aNMT) in a standardized drop vertical jump (DVJ) task and in ecologically valid sport-specific tasks performed in a simulated virtual reality (VR) environment. HYPOTHESIS:Both training groups will display beneficial biomechanical changes in the standard DVJ, but aNMT will have greater transfer to the VR sport-specific scenario. Biomechanical improvements in DVJ will vary by sport, while improvements in VR sport-specific scenarios will not vary by sport. STUDY DESIGN:Prospective longitudinal randomized placebo-controlled trial. LEVEL OF EVIDENCE:Level 1. METHODS:A total of 271 adolescent female soccer, basketball, and volleyball athletes performed 6 weeks of preseason NMT with additive aNMT or sham aNMT. Three-dimensional biomechanics were assessed at pre-/post-training that included DVJs and sport-specific VR tasks. Pre-/post-training standardized delta scores for both tasks were computed for hip and knee angles and external joint moments. Hierarchical clustering and chi-square analyses (omnibus and within each sport) assessed sport by intervention interactions for biomechanical transfer to both tasks. RESULTS:Hierarchical clustering identified 3 DVJ clusters, 2 of which (N = 243) demonstrated beneficial pre-/post-training changes. A small proportion (10%) of athletes classified in a maladaptive cluster that consisted predominantly of aNMT participants, while sham aNMT made up a greater proportion of a beneficial adaptive cluster (χ2 = 6.06; P = 0.05). For the sport-specific VR task, 2 statistical clusters were identified, both characterized primarily by improved hip flexion angles regardless of sport. CONCLUSION:Beneficial effects of aNMT and sham aNMT on the DVJ were observed in most participants, with aNMT accounting for a greater proportion of players exhibiting maladaptive DVJ changes. VR scenarios revealed consistently beneficial changes in landing biomechanics in all participants. CLINICAL RELEVANCE:Sport-specific VR tasks may assess more nuanced levels of movement complexity than traditional laboratory-based tasks and provide a complementary approach to evaluate biomechanical adaptations resulting from NMT.
BACKGROUND:Training load is widely recognized as an important contributor to injury occurrence in sport; however, athletes exposed to similar workloads may differ in their ability to tolerate and recover from training demands. HYPOTHESIS:Injury occurrence in competitive athletes is hypothesized to be more strongly associated with the interaction between training load and recovery status than with training-load magnitude alone, and reductions in recovery status are expected to precede injury onset. STUDY DESIGN:Retrospective longitudinal observational study. LEVEL OF EVIDENCE:Level 3. METHODS:A retrospective longitudinal dataset comprising 15,420 monitored training sessions from 156 competitive athletes was analyzed. Training load was quantified using session-based workload measures derived from training intensity and duration. Recovery status was evaluated using a composite indicator derived from sleep quality, perceived recovery, fatigue, and stress-related measures. Injury outcomes were examined using generalized estimating equation logistic regression models to account for repeated observations within athletes. RESULTS:Higher training loads were associated with greater injury occurrence (odds ratio [OR], 1.15; 95% CI, 1.02-1.30), whereas higher recovery status was associated with lower injury odds (OR, 0.97; 95% CI, 0.97-0.98). The association between training load and injury occurrence was more pronounced among athletes with impaired recovery, while comparable workloads showed weaker associations when recovery status was moderate or high. Recovery levels declined across the sessions preceding injury onset, with the largest reductions observed during the final sessions before injury. CONCLUSION:Injury occurrence in competitive athletes appears to be more closely associated with the interaction between training load and recovery status than with training-load magnitude alone. Monitoring recovery alongside training load may help practitioners identify periods of increased injury vulnerability and adjust workloads according to changes in athlete recovery status. CLINICAL RELEVANCE:Evaluating recovery status alongside training load may help practitioners identify short-term periods of increased injury vulnerability and guide context-sensitive adjustments to training demands in competitive athletes.
BACKGROUND:Current return-to-sport (RTS) testing after anterior cruciate ligament reconstruction (ACLR) lacks the visual and cognitive demands consistent with most sporting environments. Implementing RTS tests that challenge these systems may better assess RTS readiness, potentially reducing reinjuries. This study assessed the effects of additional visual-cognitive demands on single-leg vertical hop (VH) performance. HYPOTHESIS:Visual-cognitive conditions would result in reduced hop heights, success rates, and ground reaction force (GRF) impulses for both healthy controls and participants at 1 to 5 years post-ACLR, with greater reductions in those post-ACLR. STUDY DESIGN:Cross-sectional. LEVEL OF EVIDENCE:Level 3. METHODS:A total of 30 ACLR and 30 healthy control participants completed 3 successful trials for each of 4 randomized VH conditions: VH, VH + stroop test (Stroop), VH + stroboscopic visual disruption (SVD), and VH + SVD + ST (Stroop-SVD). Between-conditions and between-limb differences in success rates, hop height, and GRFs were assessed using linear mixed effects models, with sex as a covariate. RESULTS:Across all groups, success rates were lower in SVD (-17.1%; P < 0.01), Stroop-SVD (-20.3%; P < 0.01), and Stroop (-5.6%; P = 0.02) compared with VH (89.1%). Hop height was lower in SVD (-0.9 cm; P < 0.01) and Stroop-SVD (-1.0 cm; P < 0.01) than VH (19.6 cm). In the ACLR group, hop height was lower in the surgical limb compared with the nonsurgical limb (-1.2 cm; P < 0.01), across all test conditions. CONCLUSION:SVD and Stroop-SVD conditions resulted in reduced success rates and hop height in both groups. Although participants post-ACLR displayed surgical limb VH deficits, SVD and Stroop-SVD did not further impair ACLR group performance compared with healthy controls. CLINICAL RELEVANCE:The VH protocol was found to be reliable and challenged participants enough to induce errors in both healthy participants and those 1 to 5 years post-ACLR.
CONTEXT:Lower-limb injuries are common in soccer. The landing error scoring system (LESS) is used widely for field-based movement screening, yet its psychometric properties and prognostic value in soccer populations remain uncertain. OBJECTIVE:To synthesize evidence on the reliability, validity, and prognostic utility of the LESS among soccer participants. DATA SOURCES:PubMed, Web of Science, Cochrane Library, CNKI, and Wanfang were searched from inception to August 2025. STUDY SELECTION:Studies were included if they involved soccer participants and reported LESS-related reliability, validity, or prognostic outcomes. Modified versions of the LESS were included only when their scoring framework was clearly described and broadly comparable with the original tool. STUDY DESIGN:Systematic review with exploratory meta-analysis. LEVEL OF EVIDENCE:Level 2 to 4. DATA EXTRACTION:Two reviewers independently screened studies, extracted data, and assessed methodological quality using a modified Newcastle-Ottawa Scale. Reliability and validity outcomes, including intraclass correlation coefficients (ICCs) and agreement with 3-dimensional (3-D) motion analysis, were summarized descriptively. Prognostic metrics, including odds ratios (ORs) and area under the curve values, were extracted when available. When ≥2 comparable prospective cohorts were available, an exploratory random-effects meta-analysis was performed. RESULTS:A total of 10 studies met the inclusion criteria. In soccer settings, the LESS demonstrated excellent intra-rater reliability (ICC ≈ 0.90-0.95) and good inter-rater reliability (ICC ≈ 0.84-0.95), with item-dependent convergent validity versus 3-D kinematics. Evidence for prognostic utility was inconsistent across cohorts. Exploratory pooling of 2 comparable prospective studies showed that higher preseason LESS scores were associated with greater odds of subsequent lower-limb injury (pooled OR, 9.31; 95% CI, 3.11-27.91; I² = 0%). However, this pooled estimate should be interpreted cautiously because it was based on only 2 studies with variable injury definitions. CONCLUSION:The LESS is reliable and shows acceptable construct validity in soccer participants, but evidence for its prognostic utility remains inconsistent. It should not be interpreted as a stand-alone predictor of injury risk. Clinically, the LESS may serve as a low-cost, field-based assessment of landing movement quality within a broader multifactorial screening framework.
BACKGROUND:Lateral ankle sprains often damage the anterior talofibular (ATFL) and calcaneofibular (CFL) ligaments. Delayed peroneal muscle reaction time (reaction-time) and reduced peroneal muscle strength (strength) may increase the risk of recurrent sprains. Relationships between neuromuscular impairments and ligament strains remain unclear due to challenges in directly measuring ligament strains under dynamic conditions. HYPOTHESIS:Reaction-time and strength are correlated significantly with ATFL and CFL strains in people with and without chronic ankle instability (CAI). STUDY DESIGN:Cross-sectional study. LEVEL OF EVIDENCE:Level 3. METHODS:Participants with CAI (n = 35) and without CAI (n = 35) were recruited. Reaction-time was assessed using a trapdoor test, while strength was measured through a standardized isometric strength test. ATFL and CFL strains were calculated using a 3-dimensional rigid-body foot model during a drop-landing task. Data were analyzed using Pearson's correlations and multiple regressions. RESULTS:Compared with people without CAI, those with CAI exhibited longer reaction-time (P < 0.001) and weaker strength (P = 0.02). Reaction-time correlated with ATFL strain in both CAI (r = 0.589; P < 0.001) and non-CAI (r = 0.423; P = 0.01) participants, and with CFL strain only in CAI participants (r = 0.358; P = 0.04). Strength correlated with ATFL strain in both groups (CAI: r = -0.462, P = 0.005; non-CAI: r = -0.358, P = 0.04), but showed no correlation with CFL strain in either group. Multiple regression analysis revealed that reaction-time and strength were significant predictors of ATFL strain, with reaction-time having a greater impact (β = 0.565; P < 0.001) than strength (β = 0.431; P = 0.001). In non-CAI participants, reaction-time and strength had similar predictive contributions (β = 0.600 and β = 0.552, respectively; all P < 0.001). CONCLUSION:Both reaction-time and strength were associated with ATFL strain in people with and without CAI. Reaction-time appeared associated more closely with ATFL strain than strength. CLINICAL RELEVANCE:These findings highlight the importance of targeting neuromuscular reaction time and peroneal strength in rehabilitation programs aimed at reducing lateral ankle ligament strain and risk of recurrent sprains, with particular emphasis on improving rapid neuromuscular activation.
BACKGROUND:Swimmer's shoulder is a highly prevalent, multifactorial overuse condition in competitive athletes, often involving glenohumeral microinstability, scapular dyskinesis, and muscular imbalance. Repetitive unilateral breathing patterns may create a substantial asymmetrical load, exacerbating early periscapular fatigue and contributing to symptomatic instability on the breathing side. HYPOTHESIS:A targeted 8-week rehabilitation protocol focusing on periscapular control and rotator cuff rebalancing will result in a significant and sustained reduction in pain and improved strength symmetry in hyperlax elite swimmers presenting with shoulder pain on the breathing side. STUDY DESIGN:Retrospective monocentric cohort study. LEVEL OF EVIDENCE:Level 3. METHODS:A total of 14 elite swimmers (Beighton ≥5 out of 9) with shoulder pain on the breathing side and negative magnetic resonance imaging scan for acute lesions were enrolled. Maximal voluntary isometric contraction (MVIC) strength of the upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT), internal rotators (IRs), and external rotators (ERs) was measured using a handheld dynamometer at 1- and 2-year follow-up (1FU and 2FU) after an 8-week rehabilitation program. Pre- to post-treatment changes were assessed using paired Student's t tests. RESULTS:At 2FU, statistically significant and clinically relevant strength gains were observed in the MT (+24.9%; P = 0.002), LT (+53.6%; P = 0.001), IRs (+66.7%; P < 0.001), and ERs (+100.0%; P < 0.001). Mean visual analog scale pain scores decreased from 3.7 ± 1.0 at baseline to 0.85 ± 0.5 at final follow-up, corresponding to an 87.8% reduction (P < 0.001), indicating a durable restoration of functional shoulder balance. CONCLUSION:An individualized, asymmetry-aware rehabilitation program focusing on MT/LT reactivation and balanced IR/ER strengthening yields highly significant and durable functional gains and pain relief in hyperlax elite swimmers. The strength profile suggests a favorable shift away from compensatory UT activation toward optimal scapular stabilization. CLINICAL RELEVANCE:Targeted scapular (MT/LT) reactivation and balanced rotator cuff rebalancing effectively reduce pain and restore functional symmetry in hyperlax elite swimmers presenting with unilateral breathing-induced microinstability.
BACKGROUND:Priming strategies are used to enhance neuromuscular performance before competition, yet the effects of isometric (ISO) priming on sprint mechanical determinants and change of direction (COD) performance remain unclear in youth soccer players. HYPOTHESIS:An ISO priming session may improve COD performance and horizontal force-velocity (FV) profile variables, and participants' strength levels may be associated with individual performance responses. STUDY DESIGN:Randomized crossover trial. LEVEL OF EVIDENCE:Level 2. METHODS:Ten male youth soccer players completed 2 conditions during training performed 3 days before match-play: an ISO condition (isometric midthigh pulls [3 × 3 repetitions of 3 seconds, with 10 seconds between repetitions and 2 minutes between sets]) and a control condition comprising their usual soccer training. Horizontal FV profile variables, 30-meter sprint, and modified 505 COD performance were assessed before and 24 hours after each condition. Exploratory regression analyses examined associations between participants' strength levels and performance responses. RESULTS:Significant time × condition interactions were observed for FV-profile theoretical maximal force (F0) and modified 505 with the nondominant leg (505-ND), both improving after ISO (P ≤ 0.05). However, sensitivity analyses indicated that the 505-ND response was influenced by condition sequence (P = 0.003). In contrast, ISO decreased FV-profile theoretical maximal velocity (V0) and worsened the decrease in force orientation with increasing velocity (both P ≤ 0.05). No significant interactions were found for 30-meter sprint time or modified 505 with the dominant leg, although 30-meter sprint time increased similarly across both conditions. Relative peak force was associated with changes in 505-ND performance (r = 0.633; P = 0.05). CONCLUSION:ISO priming may represent a practical, low-fatigue strategy to enhance selected force-oriented performance in youth soccer players, although effects on velocity-oriented sprint outcomes appear limited. Exploratory analyses also suggest that baseline relative strength may influence individual responsiveness to this strategy, particularly for COD performance. CLINICAL RELEVANCE:ISO priming may help enhance horizontal force production during competitive microcycles in youth soccer players and may provide benefits for selected COD outcomes. However, these benefits may not extend to velocity-dependent outputs, supporting its use as a complementary and individualized priming strategy.
BACKGROUND:Ankle sprain (AS) is among the most common musculoskeletal injury, particularly in women. Hormonal fluctuations during the menstrual cycle may contribute to this sex disparity by affecting ligamentous laxity and muscle stiffness. While oral contraceptive pills (OCPs) modulate hormone levels and have been linked to reduced anterior cruciate ligament (ACL) injuries, there is limited evidence on the correlation of OCPs with AS. HYPOTHESIS:OCP use is associated with decreased odds of AS in a large national cohort. STUDY DESIGN:Case-control study. LEVEL OF EVIDENCE:Level 4. METHODS:The 2010-2023 PearlDiver database was queried for female patients aged 15 years to 50 years old with and without AS, identified from orthopaedic and control populations, respectively. Controls were subsequently matched 1:1 to AS patients. Each cohort was stratified by OCP use, defined as OCP prescription within 1 year before AS, and subcategorized by OCP formulation. Multivariate analysis was used to investigate independent predictors of AS, including OCP use, with secondary analysis for OCP type. RESULTS:In total, 1,836,163 patients with ASs and 108,761 controls met inclusion criteria. On average, the AS cohort was older (30.3 vs 27.5 years; P < 0.001), had a higher comorbidity index (1.9 vs 1.0; P < 0.001), and had a higher proportion of patients with severe obesity (5.4% vs 2.2%; P < 0.001). Postmatch multivariate analysis showed OCP use to be associated with decreased odds of ASs (odds ratio [OR], 0.47; 95% CI, 0.46-0.49; P < 0.001). Nonestrogen formulations had a greater protective effect (OR, 0.20; 95% CI, 0.18-0.22; P < 0.001) compared with estrogen-progesterone OCPs (OR, 0.47; 95% CI, 0.46-0.48; P < 0.001). CONCLUSION:Patients using OCP were found to have significantly decreased odds of AS compared with non-OCP patients. CLINICAL RELEVANCE:These findings may guide future treatment and injury prevention plans, particularly for at-risk female athletes.
BACKGROUND:Sidestep cutting (SSC) is used widely to examine surrogate markers of anterior cruciate ligament (ACL) loading, but the combined influence of sex and task anticipation (anticipated vs unanticipated) on whole-body biomechanics during 90° cutting remains unclear. HYPOTHESIS:It was hypothesized that sex and task anticipation would exert distinct and interactive effects on trunk, pelvic, and lower-limb biomechanics during 90° cutting, with sex exerting the dominant influence. STUDY DESIGN:Controlled laboratory study. LEVEL OF EVIDENCE:Level 3. METHODS:A total of 44 competitive amateur athletes (20 women, 24 men) performed anticipated and unanticipated 90° sidestep cuts. Whole-body 3-dimensional kinematics and lower-limb kinetics were captured. Statistical parametric mapping tested main and interactive effects of sex and task anticipation across stance (P < 0.05). RESULTS:No sex × task anticipation interactions emerged. Sex main effects spanned all variables and longer stance periods, whereas task anticipation main effects involved fewer variables and shorter intervals. Men demonstrated greater trunk and knee flexion and larger early-stance net knee flexion, varus, and external-rotation knee moments, whereas women showed a more upright trunk and pelvis with less hip and knee flexion and greater knee abduction (valgus) angles. Unanticipated cuts elicited short, phase-specific changes, including early trunk lean and reduced pelvic mobility, mid-stance hip and knee moment modulation, and late-stance ankle inversion and internal rotation changes, and attenuated braking forces. CONCLUSION:Sex was the dominant determinant of 90° SSC kinematics, joint moments, and ground-reaction forces, with effects spanning longer stance intervals than the phase-ordered proximal-to-distal differences between anticipated and unanticipated cuts, reinforcing the value of whole-body, multiplanar whole-stance interpretation. CLINICAL RELEVANCE:Given larger and more sustained sex effects, sex-specific benchmarking may aid interpretation and individualization. Progressive exposure to unanticipated 90° cutting - building from planned, lower-demand conditions - may emphasize coordinated, multiplanar control across stance.
BACKGROUND:Futsal is characterized by intermittent high-intensity actions that impose substantial external (EL) and internal (IL) load demands. Although load monitoring using accelerometry and perceptual measures is widely applied, the interaction between EL, IL, and wellness status across the competitive microcycle in elite futsal players, particularly regarding task specificity, remains unclear. The aims were to (1) analyze the effects of microcycle day and task specificity on EL, IL, and wellness status; and (2) examine the relationships between these variables. HYPOTHESIS:Training sessions with higher task specificity would elicit greater EL, IL, and wellness disturbances, with match day (MD) presenting the highest load values. STUDY DESIGN:Prospective observational study. LEVEL OF EVIDENCE:Level 3. METHODS:Ten professional futsal players (age, 25.4 ± 4.8 years) from the Spanish first division were monitored during 43 training sessions and 11 official matches. Variables included microcycle day, task specificity, EL measured by accelerations (≥2 m/s2) and decelerations (≤-2 m/s2), IL assessed using rating of perceived exertion (RPE), and wellness status evaluated through the Hooper index (HI), including delayed onset muscle soreness (DOMS), stress, fatigue, and sleep. RESULTS:MD produced significantly higher EL and RPE values (P = 0.04 to P < 0.001) than most training sessions. Among training sessions, those conducted 3 days before MD (MD-3) exhibited the highest task specificity, EL, and RPE. Strong positive correlations were found between task specificity and EL (rho = 0.85; P < 0.001), task specificity and RPE (rho = 0.80; P < 0.001), task specificity and fatigue (rho = -0.45; P < 0.001), EL and RPE (rho = 0.80; P < 0.001), and EL and fatigue (rho = -0.30; P = 0.03). CONCLUSION:Microcycle day and task specificity significantly influenced EL, IL, and fatigue during the competitive microcycle in professional futsal. Sessions with higher task specificity exhibited greater EL and IL, highlighting the importance of tailoring training tasks to modulate player load. CLINICAL RELEVANCE:Accurate monitoring and management of training load enhances understanding of the relationship between training stimuli and players' adaptive responses, supporting performance optimization and informing strategies for injury prevention and rehabilitation.
Background: Failing to obtain adequate sleep has been associated previously with greater postconcussion symptom burdens and protracted neurocognitive recovery. Sleep-related symptoms may delay concussion recovery. Active military populations frequently obtain less sleep than is recommended. Hypothesis: Cadets and midshipmen who reported less sleep experienced prolonged recovery trajectories postconcussion. Study Design: Retrospective observational cohort. Level of Evidence: Level 4. Methods: Study participants were military service academy members from 4 United States (US) Service Academies. The primary outcome of interest was the association between sleep duration recorded during the initial concussion injury assessment and time to unrestricted return to activity (URTA). Participants were divided into groups based on sleep duration (<6, ≥6 to <7, ≥7 to ≤8, >8 hours). Kaplan-Meier survival estimates were calculated for different recovery milestones, including time (days) from initial injury to clearance for URTA, and from initiation of a graduated return to activity (GRTA) protocol and URTA clearance. Univariate and multivariable Cox proportional-hazards regression models were used to estimate hazard ratios and 95% CI for recovery by sleep group. Results: During the study period, 1339 participants (39% female; age, 19.4 ± 1.5 years; height, 175.1 ± 14.8 cm; weight, 74.1 ± 15.2 kg) sustained a concussion. Participants reporting <6 hours of sleep at their initial injury evaluation took 19% longer to reach URTA when compared with participants reporting ≥7 hours to ≤8 hours of sleep. These participants also displayed GRTA protocol durations that were 18% longer than those reporting ≥7 hours to ≤8 hours of sleep. Conclusion: Sleep duration influenced postconcussion recovery trajectories. Participants who reported <6 hours of sleep took significantly longer to reach URTA. Clinical Relevance: The amount of sleep obtained before a concussion and during a postconcussion recovery trajectory may impact the total recovery duration.
BACKGROUND:Female reproductive hormones are attributed to the higher rate of musculoskeletal (MSK) injuries among female athletes compared with male athletes. PURPOSE:To evaluate association between exposure to hormonal contraceptives (HCs), joint laxity, and number of injuries in female athletes over a 1-year period. STUDY DESIGN:Cohort study. LEVEL OF EVIDENCE:Level 3. METHODS:Professional and Division I collegiate female athletes were recruited into 2 groups based on HC status (HC vs non-HC). Serum relaxin, estrogen and progesterone levels, knee laxity, generalized hypermobility, and lower extremity kinematics during a single-legged jump were examined during preseason in the luteal phase of each athlete's menstrual cycle. Injuries were tracked for 1 year after testing. RESULTS:Circulating levels of progesterone (non-HC, 38.9 ± 15.0 pg/mg vs HC, 28.6 ± 11.4 pg/mg; P < 0.01), estrogen (non-HC, 2.80 ± 3.0 pg/mg vs HC, 2.0 ± 3.0 pg/mg; P = 0.01), and relaxin (non-HC, 0.26 ± 0.08 pg/mg vs HC, 0.22 ± 0.03 pg/mg; P = 0.04) were lower in HC (n = 32) than in non-HC (n = 40) athletes during the luteal phase of the cycle. Non-HC athletes demonstrated significantly greater hip flexion at initial contact (non-HC, 29.42°± 7.64° vs HC, 25.25°± 7.13°; P = 0.02), and greater knee adduction (valgus) at maximum knee flexion (non-HC, -1.90°± 3.25° vs HC, -0.25° ± 3.40°; P = 0.02) during a single-legged drop. Average (±SD) injury count for non-HC athletes was 0.71 (±1.3) compared with 0.35 (±0.70) in the HC group (P = 0.25). Injury count was correlated significantly to circulating levels of relaxin (r = 0.32; P < 0.01). CONCLUSION:A potential relationship between increased circulating relaxin levels and the risk of injury was established. Athletes taking HCs demonstrated significantly reduced peak knee adduction angles when landing from a jump. CLINICAL RELEVANCE:The results advance knowledge of relationships between specific hormones and injury risk, and the potential role of HCs on kinematic patterns when landing from a jump. Future research will determine HC formulations that may protect against MSK injury, and inform broader strategies to reduce sport-related injury risk in female athletes.
BACKGROUND:Anterior cruciate ligament (ACL) rupture is a devastating injury that occurs 3 to 7 times more frequently in women footballers than in their male counterparts. Identifying players at elevated risk is critical for targeted injury prevention; however, no ACL injury prediction model has undergone external validation in women. Therefore, this study aimed to externally validate a field-based ACL injury prediction model in women footballers. HYPOTHESIS:A previously developed field-based ACL injury prediction model would demonstrate good predictive performance in an independent cohort of women footballers. STUDY DESIGN:Prospective cohort study. LEVEL OF EVIDENCE:Level 2. METHODS:Women footballers (n = 320) completed preseason assessments of single-leg hop kinematics, countermovement jump (CMJ) kinetics, hip adductor/abductor strength, and self-reported injury history. Players were followed prospectively for 18 months for noncontact ACL injuries. Model performance was evaluated via discrimination (area under the curve [AUC]) and calibration (observed versus predicted risk). The model was updated subsequently using the combined development and validation cohorts (n = 642), incorporating the hip adductor/abductor strength ratio and ipsilateral trunk flexion angles. Internal validation was performed via bootstrapping. RESULTS:In the external validation cohort, the original model demonstrated reduced discrimination (AUC, 0.67; 95% CI, 0.49-0.82) and poor calibration (intercept, -0.79; slope, 0.53), indicating risk overestimation. The updated 5-variable model improved discrimination (apparent AUC, 0.76; optimism-corrected AUC, 0.72; 95% CI, 0.61-0.82), and calibration intercept (-0.00), but the calibration slope (1.38) and instability across bootstrapped samples indicated imprecise individual risk estimates. CONCLUSION:The original ACL injury prediction model did not generalize well to an independent cohort of women footballers. Although model updating improved overall predictive performance, calibration remained suboptimal, and predictions were unstable. Field-based strength and biomechanical assessments may support group-level ACL injury risk stratification but are not yet suitable for precise individual risk prediction. CLINICAL RELEVANCE:Field-based measures of strength and biomechanics can help identify groups of women footballers at elevated ACL injury risk, achieving 72% classification accuracy. These screening measures are practical and scalable, requiring <10 minutes per player, and assess modifiable factors that may inform targeted injury prevention strategies.
BACKGROUND:Recent trends show a rise in sports-related surgeries among adolescents, alongside an increase in mood disorders in this group, suggesting a complex interplay between psychological health and surgical recovery. This observation has underscored the need for a focused study on how preoperative psychological states influence postoperative complications in adolescent athletes. HYPOTHESIS:Preoperative mood disorders negatively affect postoperative complications in adolescents undergoing sports-related surgeries. STUDY DESIGN:Cohort study. LEVEL OF EVIDENCE:Level 2. METHODS:Using data from the Atropos Health Eos Dataset, this retrospective cohort study examined 6805 adolescents without mood disorders and 525 with mood disorders who underwent sports surgeries between January 2015 and August 2023. We analyzed the impact of preoperative mood disorders on early postoperative healthcare utilization, primarily follow-up visit attendance. We contextualized these findings alongside complication rates using multivariable logistic regression, propensity score matching, and standardized mean differences to control for baseline disparities. RESULTS:Adolescents with preoperative mood disorders were significantly less likely to attend postoperative follow-ups (odds ratio [OR], 0.633; 95% CI, 0.469-0.853; P = 0.003), indicating potential challenges in engagement with postoperative care. There were no statistically significant differences in postoperative complications between the groups. CONCLUSION:Our findings suggest that mood disorders are not associated with a higher incidence of early postoperative complications but may contribute to lower adherence to postoperative follow-up care. This finding underscores the importance of identifying psychological factors that may affect healthcare engagement, and highlights the need for support strategies for adolescents with mood disorders. CLINICAL RELEVANCE:Understanding how mood disorders may influence healthcare engagement and follow-up utilization can inform future screening and intervention strategies. Tailoring postoperative follow-up protocols to address the psychological needs of these patients may enhance overall outcomes and athlete satisfaction with their surgical recovery.
CONTEXT:Historically, physical fitness and exercise training interventions have often been described in relation to training volume metrics (e.g., total sets, repetitions, and session duration). Training frequency and overall training load, which integrates volume, frequency, and intensity, are related but conceptually distinct constructs that are commonly reported alongside volume measures. Although easily quantifiable, these metrics do not reflect outcome performance, such as function, health, wellbeing, quality of life, or the burden of obtaining these outcomes. Emerging evidence suggests that these benefits may be achieved with much smaller doses of training, although a unified framework for performance efficiency is lacking. OBJECTIVE:To systematically review existing literature on exercise dosing, volume, and time efficiency in relation to function, performance, and patient-reported outcomes (PROs), and propose a conceptual framework for the new term "value-based performance" (VBP). DATA SOURCES:The literature databases PubMed (MEDLINE), Web of Science, and Scopus were searched using Boolean operators and combined free-text keywords for the relevant studies reported in accordance with the PRISMA 2020 guidelines. STUDY SELECTION:Studies were selected if they explicitly evaluated the relationship among exercise dose, volume, time and performance, function, and PROs. After stepwise screening and full-text review, 9 studies that met eligibility criteria were qualitatively synthesized, and data on the outcomes gained and the costs of training were extracted and used to build the conceptual framework. STUDY DESIGN:Systematic review with qualitative thematic analysis. LEVEL OF EVIDENCE:Level 3. DATA EXTRACTION:Data extraction focused on parameters related to exercise dose, volume, time, performance, function, and use of PROs. RESULTS:Across resistance, aerobic and high-intensity interval training, time-efficient reduced-dose showed small-to-moderate benefits to performance, functional capacity, and PROs. There was strong evidence for maintenance of benefits, favorable outcome-to-burden ratios, minimum effective dose thresholds and clinically meaningful changes, and less time to benefit. CONCLUSION:This review challenges the conventional, volume-focused definition of performance and that efficiency should also be considered when evaluating exercise. We propose a new approach to defining performance, termed VBP, which describes performance as the ratio of gain in your outcome(s) relative to the cost of obtaining those gains.
CONTEXT:Hamstring muscle strain is a common sports injury associated with significant time loss and high recurrence rates among athletes. Eccentric exercises, particularly the Nordic hamstring exercise (NHE), are effective in reducing injury incidence, yet their morphological adaptations remain underexplored. OBJECTIVE:To examine exercise-induced morphological adaptations of the hamstring muscles and to provide an integrated perspective on changes in muscle architecture and size. DATA SOURCES:In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, PubMed, Scopus, Cochrane Library, and Web of Science were searched up to December 2024. STUDY SELECTION:Randomized controlled trials including adults (≥18 years old), with or without hamstring injuries, that investigated hamstring-strengthening interventions and assessed postintervention muscle morphology using magnetic resonance imaging (MRI) or ultrasonography were included. STUDY DESIGN:Systematic review. LEVEL OF EVIDENCE:Level 1. DATA EXTRACTION:Information on sample characteristics, exercise prescription, intervention details, exercise type, assessment device, targeted muscles, measured parameters, and outcomes was extracted. RESULTS:A total of 14 studies, involving 382 participants, were included. Eccentric exercises demonstrated the most consistent adaptations, particularly increases in fascicle length (FL) and reductions in pennation angle (PA) in the biceps femoris long head (BFlh). Evidence for changes in muscle volume (MV) and cross-sectional area (CSA) was more heterogeneous across intervention types and imaging modalities. Muscle thickness showed limited or inconsistent changes across studies. Ultrasound (US) and MRI assessed different aspects of muscle morphology, limiting direct comparison across modalities. MRI-based studies more consistently demonstrated changes in MV and CSA, whereas US-based studies reported primarily architectural parameters such as FL and PA. CONCLUSION:Eccentric and resistance-based training were associated with favorable morphological adaptations in the hamstring muscles. Among these, eccentric strengthening interventions, particularly NHE-based protocols, were associated most consistently with increases in FL and reductions in PA of the BFlh. These findings highlight the importance of targeted exercise prescription and underscore the role of imaging modalities such as US and MRI in monitoring hamstring muscle adaptations.
BACKGROUND:Fatigue-induced changes influence physical performance of youth players during and after handball matches. HYPOTHESIS:Players with higher levels of neuromuscular performance may exhibit reduced postmatch fatigue and a faster recovery. STUDY DESIGN:A prospective, comparative, repeated-measures observational design was used. LEVEL OF EVIDENCE:Level 3. METHODS:A total of 34 outfield male youth handball players participated in this study (age, 15.42 ± 1.65 years; height, 171.31 ± 9.92 cm; body mass, 64.68 ± 15.14 kg). Each participant played 1 simulated match during the in-season phase. Neuromuscular performance was evaluated pre-, post-, 24 hours post-, and 48 hours postmatch using the maximal isometric hand grip strength test, the countermovement jump test, the 505 change of direction test, and a linear straight sprint test (i.e., 10 m, 20 m, 30 m). Moreover, perceived wellness was obtained at pre-, 24 hours post-, and 48 hours postmatch, and match-related internal and external loads were monitored. Random forest clustering was used to categorize participants into 2 clusters based on their prematch neuromuscular performance (i.e., higher- and lower-performing players). RESULTS:Higher-performing players experienced greater internal and external match loads but showed minimal postmatch performance declines (P < 0.05). During the recovery period, lower-performing players exhibited greater impairments in sprint performance while higher-performing players reported elevated perceived fatigue and exhibited greater impairments in change of direction performance (P < 0.05). CONCLUSION:Higher neuromuscular performance enables youth handball players to manifest superior physical outputs during simulated matches and minimizes the extent of match-induced acute fatigue, but the contribution to a faster recovery remains unclear. CLINICAL RELEVANCE:Training programs for youth handball players should emphasize the development of neuromuscular function, not only for enhancing match physical performance, but also for reducing acute fatigue.
