The effect of lean body mass and strength on lower extremity energy absorption strategies during landing

Lower amounts of lean body mass and strength in females compared to males have been proposed to result in greater relative task difficulty for females when asked to perform a standardized task and may explain sex differences in energy absorption strategies during landing maneuvers. The primary objective of this study was to determine the effect of lower extremity lean mass and eccentric muscle strength on lower extremity energy absorption strategies during a drop jump landing task. The secondary objective was to compare sex differences in energy absorption strategies when the task demands were equalized relative to the amount of lean mass available to dissipate kinetic energy upon landing. This was accomplished by separating out the effects of body composition and strength from other sex confounding variables by examining lower extremity lean mass and eccentric thigh strength in males and females matched by similar BMI's. Thirty-five males were matched to 35 females on body mass index, and then completed body composition testing via dual energy x-ray absorptiometry, maximal eccentric strength testing via isokinetic dynamometry, and biomechanical assessment during a drop jump landing task. Each matched pair performed the drop jump landing task from two different heights: one at a standard height, and one at a height that equalized the relative task demands for the males relative to the females' standard height. The overall hypothesis was that less lower extremity lean mass relative to body mass would predict less lower extremity energy absorption during the deceleration of landing; this relationship would be mediated by maximal eccentric thigh strength. Additionally, sex differences in energy absorption strategies were expected to diminish once the relative task demands were equalized. The results showed that males had 42% more lower extremity lean mass (p These results indicate that sex differences in energy absorption are not explained by sex differences in eccentric strength or relative task difficulty. More work is needed to determine additional factors that influence energy absorption strategies and which may further explain the sex differences in energy absorption strategies and the ultimate risk of injury