Limited predictive value of preseason isokinetic strength testing for noncontact lower extremity injuries in elite female football players: A 5-year prospective cohort study.

PURPOSE: To investigate associations between preseason isokinetic strength and subsequent noncontact lower extremity injuries in professional and elite youth female football players. METHODS: In this prospective study, 271 players (professional, under 20 [U20], under 17 [U17]) underwent preseason isokinetic testing over five seasons. Measurements included concentric/eccentric hamstring and concentric quadriceps strength (60°/s, 240°/s). Conventional, functional hamstring-to-quadriceps (H/Q) ratios and limb symmetry indices (LSI) were calculated. Group differences were assessed using linear mixed models (Group × Limb interactions), and prospective injury risk was evaluated using multivariable generalised estimating equations (GEE), accounting for multi-season participation. RESULTS: A total of 70 noncontact injuries were recorded (anterior cruciate ligament [ACL]: n = 11; meniscus/collateral ligament: n = 20; ankle: n = 21; muscle: n = 18). Linear Mixed Models revealed significant Group × Limb interactions for hamstring strength and H/Q-ratio parameters, most pronounced in the knee and muscle-injury subgroups. In GEE analysis, a lower conventional H/Q ratio was associated with a higher injury risk across the overall cohort (aOR: 0.78; 95% CI: 0.62-0.98; p = 0.03) and muscle injuries specifically (aOR: 0.67; 95% CI: 0.45-0.92; p = 0.04). A history of previous ACL injury was independently associated with an increased risk of subsequent ACL rupture (aOR: 1.73; 95% CI: 1.02-4.70; p = 0.05). Higher baseline quadriceps strength showed a nonsignificant trend towards increased muscle-injury risk (aOR: 1.60; 95% CI: 0.96-2.67; p = 0.08). No significant independent predictors were identified for ankle or non-ACL knee injuries. CONCLUSIONS: Preseason isokinetic testing possesses limited independent predictive utility for future noncontact lower extremity injuries and should therefore not be used as a standalone screening tool, although a higher hamstring-to-quadriceps ratio showed a modest protective association warranting further investigation. Instead, isokinetic profiles should be integrated into a broader, multifactorial assessment battery for athlete monitoring and rehabilitation management in elite female football. LEVEL OF EVIDENCE: Level II, prospective cohort study.