ECSS Paris 2023: OP-MH35
INTRODUCTION: The shoulder is one of the most heavily loaded joints in overhead sports, particularly elite-level volleyball, where repetitive high-speed movements impose substantial mechanical demands. Effective neuromuscular control and the ability to exert force are essential for optimal performance and injury prevention. However, there is limited longitudinal data on the seasonal evolution of shoulder strength in high-level athletes, which reduces our understanding of role- and angle-specific changes and compromises the optimisation of preventive protocols and load management. This study aims to characterise these patterns to support targeted, periodized preventive strategies. METHODS: Thirteen elite right-handed female volleyball players from a Romanian top-division team (aged 19–35) were assessed longitudinally at three time points across the season—start (T0), mid-season (T1), and end (T2)—using a PitchSix Force Board digital dynamometer. Athletes were categorised by role (9 hitters, 2 setters, 2 liberos). Strength was assessed bilaterally and included isometric IR and ER at 0°, 45°, 60°, and 90° of abduction and the Jobe test at 30°. Joint mobility was assessed via GIRD and external-rotation ROM. All tests were performed under standardised conditions with two trials per limb (5-s maximal isometric contractions; 15-s rest between trials). RESULTS: At T0, 13 elite athletes displayed role- and angle-dependent IR/ER profiles, showing differences by role and angle with a slightly imbalanced IR/ER ratio. In hitters, baseline 60° IR strength was 6.65 kg (±1.35). Between T0 and T1, all roles showed a marked increase in strength, with hitters showing the most marked increase at 0°-60° (+13-28%), followed by setters at 45°-90° (+5-27%), and liberos at 0°-90° (+6-46%). Some increases stabilised or decreased between T1 and T2, whilst hitters and liberos showed more marked decreases at 60°-90°. The Jobe test at 30° showed similar trends (+8-27% T0-T1; -4/-16% T1-T2), with a stable symmetry index (0.96-1.16). The balance index showed IR predominance at reduced abduction angles. At T2, four hitters had elevated GIRD (24°), while TROM indicated preserved total ROM. CONCLUSION: The data show that the seasonal evolution of shoulder isometric strength has clear angle- and role-specific patterns during the competitive season. Key findings were a progressive functional imbalance at high angles and more marked decreases in ER strength at 60°–90°, along with fatigue and stiffness in some athletes. These results support longitudinal monitoring frameworks integrating strength, mobility and load management. A personalised approach is essential to preserve performance and reduce shoulder overload risk.
Read CV Lorenzo CarusoECSS Paris 2023: OP-MH35
INTRODUCTION: Sport school students face cumulative physical and psychological demands that may increase injury risk. While previous research has identified associations between training load, prior injury, and burnout, most studies rely on cross-sectional or regression-based approaches that may not capture complex, non-linear and temporal interactions. This study examined whether machine learning could predict weekly incident acute and overuse injuries among adolescent sport school students by integrating psychological, workload, and injury history variables. METHODS: A longitudinal design was applied to 211 Norwegian lower secondary sport school students (Grades 8–10), contributing 2,135 healthy-week observations. Weekly surveys assessed sport-related injuries, training exposure, sport burnout, and sport engagement. Incident injuries (acute and overuse) were predicted one week ahead using a Random Forest model with balanced sampling and person-level cross-validation. Twenty-seven features capturing acute workload, chronic workload patterns, psychological states and traits, injury history, and interaction terms were included. Model performance was evaluated using cross-validated accuracy, class-specific accuracy, and one-vs-rest AUC. RESULTS: The optimized Random Forest achieved 68.3% mean cross-validated accuracy. Discriminative ability was moderate (AUC = 0.57 for acute injuries; 0.66 for overuse injuries). Injury history variables (personal injury rate and weeks since injury) were the strongest predictors. Chronic workload characteristics and workload variability contributed more to prediction than acute weekly load alone. Interaction effects were important: acute load × recent injury and engagement × recent injury ranked among the top predictors. Chronic psychological patterns, particularly long-term engagement and burnout-related inadequacy, were more predictive than weekly fluctuations. The full model significantly outperformed simplified and regression-based comparison models. CONCLUSION: Injury risk among adolescent sport school students reflects cumulative and interacting risk processes rather than isolated weekly factors. Machine learning approaches capture these non-linear and conditional patterns more effectively than traditional regression models. Early and continuous monitoring of injury history, workload stability, and psychological functioning may support more targeted and timely prevention strategies in sport school contexts.
Read CV Christian Thue BjørndalECSS Paris 2023: OP-MH35
INTRODUCTION: Hamstring strain injury (HSI) is one of the most common and severe non-contact lower-limb injuries, frequently occurring in sports that require high-speed sprinting, such as sprinting, soccer, and rugby. In recent years, both its incidence and severity have shown an increasing trend. The study aimed to investigate the incidence of hamstring injuries among collegiate athletes and to analyze the association between knee muscle strength and the risk of HSI. METHODS: A total of 257 male collegiate athletes (age 21.0 ± 1.8 years; height 179.0 ± 6.0 cm; weight 75.4 ± 8.4 kg) were enrolled, primarily participating in high-speed running sports such as sprinting, soccer, and basketball. Isokinetic dynamometry was employed to assess quadriceps and hamstring strength. Concentric quadriceps strength and both concentric and eccentric hamstring strength were measured at an angular velocity of 60°/s. The functional hamstring-to-quadriceps (H: Q) ratio was calculated as the ratio of hamstring eccentric peak torque to quadriceps concentric peak torque. HSI incidence was prospectively recorded over a 12-month follow-up period. Athletes completed a monthly online questionnaire to report any occurrence of HSI. Independent-samples and paired-samples t-tests were conducted to compare athletes with and without HSI and to compare injured and uninjured limbs, respectively. Univariate Cox regression with clustering was applied to examine the relationship between muscle strength and the risk of HSI. RESULTS: A total of 41 athletes (42 thighs; 16.0% of the study population) sustained HSI, accounting for 34.7% of all lower-limb injuries. Five athletes experienced recurrent injuries. Athletes in the injured group exhibited a significantly lower functional H:Q ratio compared with those in the uninjured group (0.70 ± 0.14 vs. 0.76 ± 0.22, P = 0.047). No significant differences were observed between groups in hamstring concentric or eccentric strength, or quadriceps strength. Similarly, comparisons between injured and uninjured limbs showed no significant differences in muscle strength or H:Q ratios. Cox regression analysis indicated that muscle strength variables were not significantly associated with the risk of HSI. CONCLUSION: Injured athletes showed a lower functional H:Q ratio, whereas overall hamstring and quadriceps strength did not differ significantly between groups or between injured and uninjured limbs, indicating that functional muscle balance may better indicate HSI than strength alone. The functional H:Q ratio may therefore be useful in preventing HSI. Consequently, preventive strategies in collegiate athletes may benefit from emphasizing dynamic muscle coordination, proper activation patterns, and functional H:Q ratio optimization rather than focusing solely on increasing hamstring or quadriceps strength.
Read CV Shangxiao LiECSS Paris 2023: OP-MH35