Functional demands on the stance limb in walking.

In normal human locomotion, the lower extremities must maintain the erect posture while at the same time permitting forward progression of the body. Walking involves a complex interplay of gravity, momentum changes, and muscle action. A quantitative analysis of the effects of gravity and momentum changes on the stance limb in normal gait has been performed. These effects, represented by the ground reaction force, impose challenges to the muscles of the lower extremity. The nature of the torques about the hip, knee, and ankle joints has been investigated and correlated with the timing of muscle action throughout the gait cycle. Mechanical events in the earliest part of stance phase have been more clearly described than in previous work. Analysis of the effects of gravity and momentum changes improves our understanding of the mechanics of normal walking, and can aid in the diagnosis and treatment of disabled patients.