In-vivo elastic and damping response of the human leg to impact forces.

The transmission of impact forces in a straight leg from the foot to the level of the greater trochanter was investigated by a two-degree of freedom linear damped-spring model. Foot ground forces measured during a vertical jump and accelerations measured at the level of the greater trochanter were used as model input. The model elastic constant and damping coefficient were determined by solving the dynamic equations of the system. The model was used to predict peak acceleration values for a given input force. Satisfactory prediction of the magnitudes of the first two peaks of the acceleration (maximum difference of 3 percent) was achieved in the two subjects studied.