The effect of repetitive drop jumps on landing mechanics

The purpose of the study was to investigate the effects of fatigue on the lower extremity landing strategies of males and females. Twelve recreationally active males (n = 6) and females (n = 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 20% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase of all jumps. At initial ground contact, males exhibited greater extension at the hip and knee and less plantar flexion than females. However, females performed more eccentric work during the impact phase of landing. Fatigue resulted in an increased extension at the hip, knee, and ankle for both genders, but did not have an effect on the peak VGRF. Fatigue also resulted in an increase in work performed at the ankle and an approximately equal reduction in work performed at the knee for both genders. Investigation of the peak powers revealed that as a result of fatigue, females utilized a landing strategy in which more energy was absorbed at the knee during the early part of the impact phase. The increased reliance on the knee musculature to dissipate kinetic energy during the impact phase of landing demonstrated by females may be a reason for the commonly seen gender disparities in injury rates. Furthermore, the shift towards energy absorption during the initial part of the impact phase when noncontact injuries are known to occur, exhibited by females, may indicate a greater injury risk for females.School of Physical Education, Sport, and Exercise ScienceThesis (M.S.