Lower-Limb Biomechanics Differ Between Sexes During Maximal Loaded Countermovement Jumps

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To improve military personnel's operational performance, this study determined the impact of heavy, military body–borne load on vertical jump performance. Twenty men and 17 women had lower-limb work and power quantified during a series of countermovement jumps with 4 body-borne loads (20, 25, 30, and 35 kg). For each jump, subjects stood in athletic position with feet shoulder-width apart, then squatted down and immediately performed a maximal-effort vertical jump. Subjects performed 3 successful jumps with each load. During each jump, limb and hip, knee and ankle work and power, each joint's contribution to limb work, as well as jump height and center of mass velocity were quantified. Each dependent measure was submitted to a 2-way repeated-meausres analysis of variance, with alpha level 0.05. Body-borne load reduced jump height (p = 0.001) but increased ankle work (p < 0.001). To jump higher (p < 0.001) with a greater center of mass velocity (p = 0.001), men produced more limb work (p < 0.001), hip (p = 0.001; p < 0.001), knee (p < 0.001; p < 0.001), and ankle (p < 0.001; p < 0.001) joint power and work. But, women produced a greater percentage of work at the ankle (p = 0.020) than men. Military practitioners may target different training adaptations to improve male and female personnel operational performance because lower-limb biomechanics differ between sexes during loaded vertical jumps.