Sex-related differences in joint-angle-specific hamstring-to-quadriceps function following fatigue.

The purpose of this study was to examine the effect of fatiguing exercise on sex-related differences in the function of hamstring and quadriceps muscles at several angular velocities and joint angles. Physically active participants (50 male: 28.7 +/- 4.5y, 1.82 +/- 0.07 m, 82.3 +/- 6.87kg; 50 female: 27.0 +/- 5.8y, 1.61 +/- 0.08 m, 68.75 +/- 9.24kg) carried out an isokinetic assessment to determine concentric and eccentric torques during knee extension and flexion actions at three different angular velocities (60/180/300 degrees/s). The H/Q(FUNCT) was calculated using peak torque (PT) values at 3 different joint-angle-specific (15 degrees, 30 degrees and 45 degrees of knee flexion). A repeated measures analysis of variance (ANOVA) was used to compare within group results. Between group comparisons of sex-related differences were assessed by independent T-tests. Fatiguing exercise in males resulted in a decrease in H/Q(FUNCT) ratios for each angle of knee flexion at both 60 degrees/s and 300 degrees/s angular velocities (p<0.05). In females, significant decreases in H/Q(FUNCT) ratios were observed following fatiguing exercise for each angle of knee flexion and angular velocity (p<0.01). Significant differences in H/Q(FUNCT) ratios following fatiguing exercise were evident between males and females at each joint angle and angular velocity (p<0.01). These findings indicate sex related differences in H/Q(FUNCT) ratios following fatiguing exercise. Females have greater reductions in torque and H/Q(FUNCT) ratios following fatigue than their male counterparts. This potentially exposes females to higher risks of injury, particularly when fatigued. Practitioners should attend to the imbalance in fatigue resistance of hamstring and quadriceps function, particularly in female athletes.