Sex Differences in Lower Extremity Kinetics and Kinematics during Landing

Abstract

1578 Anterior cruciate ligament (ACL) injuries occur relatively more frequently in female athletes than in male athletes. Recently, altered landing techniques (less knee flexion angle) in female athletes have been reported to be associated with an increase in ACL loading. However, the mechanism(s) responsible for ACL injuries and sex differences in landing techniques remain unclear. PURPOSE: To compare the kinetics and kinematics of females with those of males during two landing movements: vertical jump (VJ) and horizontal jump (HJ). METHODS: Kinetic and kinematic data were recorded during landing by 12 male and 11 female college students. Initial and peak joint angles of hip, knee, and ankle in a sagittal plane, and the time to reach peak knee flexion were determined from the kinematic data. Peak values for hip, knee, and ankle moments and powers, ground reaction force, and anterior tibial shear force were determined and normalized to body mass. Repeated measures ANOVA was used to identify sex related differences. RESULTS: During VJ, time to reach maximum knee flexion was lower for females (183 ± 36ms vs. 224 ± 36ms, p = 0.01), whereas other variables did not differ. During HJ, knee moments (3.10 ± 1.13Nm vs. 2.25 ± 0.57Nm, p = 0.04), knee power (−23 ± 6.8W/kg vs. −16 ± 6.8W/kg, p = 0.03) and time to reach peak knee flexion (female: 187 ± 33ms vs. 217 ± 35ms, p = 0.05) were significantly greater in males. CONCLUSIONS: Males and females in this study exhibited similar landing kinematics, suggesting that the kinematics per se are not responsible for the increased ACL injury rate of females. However, our results suggest that altered energy dissipation in females, as demonstrated by different time to reach maximum knee flexion, may represent a possible mechanism for increased ACL injury rates in female athletes.