The impact of joint angle and movement velocity on sex differences in the functional hamstring/quadriceps ratio.

BACKGROUND: Females are two to eight times more likely to suffer a non-contact injury compared with males thus the purpose of this study was to explore the influence of joint angle and movement velocity on sex differences in the functional hamstring to quadriceps ratio (H/QFUNC). METHODS: Isokinetic concentric and eccentric torque were determined in 110 participants (55 males and 55 females) through a 90° range of movement at 60, 120, and 240°/s. Testing was performed with the hip flexed at 10°. The H/QFUNC was determined at three specific joint angles (15, 30 and 45° flexion) and where peak torque occurred for concentric knee extension. RESULTS: A significant interaction effect (P<0.01) for sex and joint angle was observed with women demonstrating a lower H/QFUNC than males, especially at more extended knee positions. A significant sex by velocity interaction (P<0.01) indicated a lower H/QFUNC in women as velocity increased. Significant main effects (P<0.01) indicated that irrespective of sex the H/QFUNC increased as the knee extends and velocity increases. CONCLUSION: Given the reduced H/QFUNC in females compared to males at more extended knee positions and faster velocities, this may contribute to the observed sex bias in reported injury rates.

Electromechanical delay of the hamstrings during eccentric muscle actions in males and females: Implications for non-contact ACL injuries.

Sex differences in neuromuscular functioning has been proposed as one of the factors behind an increased relative risk of non-contact anterior cruciate ligament (ACL) injury in females. The aim of this study was to explore sex differences in electromechanical delay (EMD) of the hamstring muscles during eccentric muscle actions and during a range of movement velocities. This study recruited 110 participants (55 males, 55 females) and electromyography of the semitendinosus, semimembranosus and biceps femoris was determined during eccentric actions at 60, 120 and 240°/s. No significant sex differences were observed irrespective of muscle examined or movement velocity. Irrespective of sex EMD significantly increased with increasing movement velocity (P < 0.01). There was no significant difference in the EMD of the 3 muscles examined. Our findings suggest that during eccentric actions of the hamstrings that there are no sex differences, irrespective of movement velocity. This would suggest that other factors are probably responsible for the increased relative risk of non-contact ACL injury in females compared to males.