Biomechanical gender differences of the ankle joint during simulated half-squat parachute landing

Introduction: A search of the literature did not reveal known gender differences in biomechanics during parachute landing. Methods: Eight male and eight female healthy adults participated in this experiment. Each individual jumped from platforms with three different heights (low: 0.32 m; medium: 0.52 m; and high: 0.72 m) and landed on flat ground in a standard half-squat parachute landing technique. The ground reaction force (GRF) normalized to bodyweight (BW), ankle joint kinematics, and the surface electromyogram (EMG) signals of the tibialis anterior (TA) and lateral gastrocnemius (LG) were measured. Two-way ANOVA was used to analyze the effects of the dropping height and gender factors. Results: The anterior-posterior GRF (men 1.01 BW; women 0.79 BW), rate of loading (men 260 BW · s^-1; women 127 BW · s ^-1), and absolute EMG amplitude of TA (pre-landing: men 219 μv; women 129μv; post-landing: men 573 μv; women 288μv) in the men's group were significantly higher than in the women's group, whereas peak angular velocity of dorsiflexion in the women's group (1627° · s ^-1) was significantly higher than in the men's (1188° · s^-1). Discussion: Women are prone to transform the kinetic energy to the ankle motion, whereas men are more likely to transform it to friction. The co-contraction of the ankle flexor and extensor differs between genders. These factors may be associated with the higher incidence of parachute injuries among women reported by some authors.