Fig. 3. Mean hip, knee, ankle and total joint work in level walking across all subjects. Values are means ± s.d. Muscles at each joint produced both negative and positive work during the stance phase of level walking. Net work was negative at the knee but positive at the hip and ankle. Total net work was positive at 16.2 J. The magnitudes of negative and positive work were significantly different at each joint; the asterisk indicates the larger value (P<0.010).