In 15 normal adults an advanced biomechanical analysis of walking patterns at slow, natural, and fast cadences showed that the ankle had two mechanical power phases:​ a negative work phase during weight acceptance, followed by a dominant burst of positive work at push-off. The knee had four power phases:​ a negative work phase at weight acceptance, a small positive work phase during mid-stance, a major negative work burst at push-off and early swing, and a final energy-absorbing phase at the end of swing. The power phases at the hip are quite irregular and somewhat lower than those at the knee and ankle. The dominant positive work burst by the plantarflexors drops as speed decreases, but less rapidly than the positive work by the knee muscles during mid-stance. The energy absorption by the quadriceps during weight acceptance decreases rapidly as speed decreases and at late stance decreases moderately. The energy absorption by the ankle plantarflexors during weight acceptance remains fairly constant at all walking speeds, and the absorption by the knee flexors at end of swing drops only slightly as cadence decreases.