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

Abstract

To investigate associations between preseason isokinetic strength and subsequent noncontact lower extremity injuries in professional and elite youth female football players. 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. 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. 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 II, prospective cohort study.