Biomechanical considerations of drop landing

The purpose of this dissertation is to examine differences in muscle activation, heel pad mechanical properties, and the distribution and motion of the soft tissue wobbling masses and the effects these differences have on the kinetics and kinematics of males and females during two-legged flat-footed and toe landing from a drop, in an effort to determine specific factors leading to a predisposition of women to Anterior cruciate ligament (ACL) injury.; Significantly greater vertical ground reaction forces were observed during flat-footed landings (7.0 BW) compared with toe landings (4.5 BW) for both groups. Landing phase patterns differed slightly between the sexes, with males demonstrating longer descent phases (time from initial foot contact to time of bottom-most position) for all landings. Females displayed lower absolute bottom-most center of mass position during flat-footed landings compared with males. Electromyography data revealed that certain lower extremity activation patterns differed significantly between males and females, and that landing style influenced these patterns.; Kinematic and kinetic analyses revealed limited differences between the sexes. Males exhibited significantly greater vertical ground reaction force peaks normalized with respect to body weight during both styles of landing compared with females, and demonstrated more rapid rates of loading. Males demonstrated greater knee extension at impact and at time of peak vertical ground reaction force compared with females. Joint angular velocities of the ankle were greater during toe landings compared with flat-footed landings, and males demonstrated significantly greater angular velocity at the ankle during the toe landings compared with females.; The mechanical properties of the heel pad were significantly different between the sexes. The male pads were larger, thicker, and demonstrated lower stiffness and energy losses compared with females. The use of an adjustable rigid link device externally affixed to the thigh and shank provided a rigid framework from which to reduce the error in kinematic calculation resulting from soft tissue motion. Comparison of displacement of markers placed on the soft tissue of the thigh region with those of the rigid link provided evidence of soft tissue motion opposite in phase with that of the rigid markers. (Abstract shortened by UMI.)...