Joint moment control of mechanical energy flow during normal gait.

The study purpose was to estimate the ability of joint moments to transfer mechanical energy through the leg and trunk during gait. A segmental power analysis of five healthy adult subjects revealed that internal joint extensor moments removed energy from the leg and added energy to the trunk, while flexor moments and gravity produced the opposite effects. The only exception to this pattern was during the push off phase of gait when the ankle plantar flexor moment added energy to both the leg and the trunk. Pairs of joint moments with opposite energetic effects (knee extensor vs gravity, hip flexor vs ankle plantar flexor) worked together to balance energy flows through the segments. This intralimb coordination suggests that moments with contradictory effects are generated simultaneously to control mechanical energy flow within the body during walking.