Effects of Fatigue on Peak and Angle-Specific Hamstring-to-Quadriceps Ratios in Collegiate Women Lacrosse Athletes

Background: Hamstring strains and anterior cruciate ligament (ACL) tears commonly occur in court and field sport athletes, with prevalence being higher in females. The likelihood of such injuries has been related to the hamstring-to-quadriceps (H:Q) strength ratio. Such a ratio can be affected by fatigue, to which athletes are frequently exposed. The aim of the current study was to investigate effects of fatigue on peak torque and angle-specific functional H:Q ratios at different angular velocities, as well as the association between resting functional H:Q ratios and those obtained following fatigue. Methods: A total of 18 collegiate women lacrosse players executed maximal knee concentric and eccentric contractions at angular velocities of 60, 180, and 240°/s following a supervised fatigue protocol. The isokinetic testing was then replicated. Results: There was a significant difference in functional peak torque H:Q ratios (p = 0.021–0.041) and ratios at 60 (p = 0.013–0.044), but not 20 degrees of knee flexion before and after fatigue at all three angular velocities. No main effects of angular velocity or ratio type were observed on H:Q ratio difference. The relationship between resting and fatigued functional H:Q ratios ranged from moderate to strong across all three angular velocities. Conclusions: Fatigue was associated with reductions in functional H:Q ratios, indicating altered knee flexor–extensor strength balance under fatigued conditions. In time-constrained settings, baseline functional H:Q ratio may provide practitioners with useful preliminary information regarding an athlete’s potential susceptibility to lower-limb injury after fatigue.