Age increases the skeletal versus muscular component of lower extremity stiffness during stepping down

Elderly adults step down with greater lower extremity stiffness than young adults. The purpose of this study was to compare skeletal and muscular components of lower extremity stiffness between elderly and young adults dur-ing stepping down. Fourteen elderly (age, 70.1 years) and 16 young (age, 20.8 years) adults stepped down onto a force plate from 10 % and 20 % body heights while being videotaped. Lower extremity stiffness was defined as the ratio between the floor reaction force directed along the limb and limb compression. It was partitioned into skel-etal and muscular components using the angular relationship ( f) between the direction of the force and the line of the leg. Our results showed that