Consideration of Gender Differences in Ankle Stabilizer Selection for Half-Squat Parachute Landing

Niu W, Wang Y, Yao J, Zhang M, Fan Y, Zhao Q. Consideration of gender differences in ankle stablizer selection for half-squat parachute landing. Aviat Space Environ Med 2011; 82:1118–24.

Introduction: Chinese paratroopers have traditionally performed the half-squat parachute landing (HSPL), which was different from the well-known parachute landing fall. During HSPL, ankle biomechanics have been shown to vary greatly between genders. Therefore, it is necessary to consider gender with regard to the design of ankle stabilizers for paratroopers. Methods: Eight male and eight female healthy participants landed from platforms under three ankle conditions based on different stabilizer rigidity levels (barefoot control, elastic tape, and semi-rigid brace). Multivariate analysis of variance was used to analyze the effects and interactions of ankle stabilizer, gender, and dropping height on the ground reaction forces (GRF), ankle kinematics, and the shank surface electromyogram (EMG). Results: Compared to men, women had significantly higher peak medial-lateral GRF when they were equipped with stabilizers (tape: men 0.521 vs. women 0.856 bodyweight; brace: men 0.531 vs. 0.935 bodyweight), except when barefoot. Both stabilizers significantly decreased all peak angular displacements, but no significant interaction was detected between gender and stabilizer rigidity in ankle kinematics. Compared to barefoot, the semi-rigid brace significantly increased male pre-landing EMG amplitude of the tibialis anterior from 218 to 525 μV and post-landing EMG amplitude of the lateral gastrocnemius from 323 to 910 μV, but no corresponding change took place in women. Discussion: The semi-rigid stabilizer was helpful for men in increasing shank muscle activities. Increased stabilizer rigidity had little influence on the muscle activities of women and this could contribute to greater injury risk in women during HSPL.