The effects of mass loading distribution on walking energetics

The aim of this study is to determine the effects of mass load distribution on walking energetics and mechanics. Twelve healthy adults (23 ± 2 yrs) walked on a treadmill at 1.25 m/s with no load and an external load (5% of body weight). Loads were placed on different locations (foot, shank, thigh, waist, trunk and head) of the body. We determined walking energetics using indirect calorimetry during the last two minutes of each sixminute trial. In addition, walking mechanics were quantified for 10 strides of each trial. A multivariate analysis of variance (MANOVA, p.05) was used to determine the statistical differences between load positions on net metabolic power and walking mechanics. Planned contrasts were used to determine the relative effect of upper versus lower body loading and no load versus loaded positions. Results showed that vertical load position had a significant effect on net metabolic power during walking (p=.001) but had no significant effect on spatiotemporal characteristics, stride kinematics, inverted pendulum recovery, or mechanical work (p.05). Nonetheless, planned comparisons revealed that lower body mass loading elicited a significantly greater metabolic cost as compared to upper body loading (p=.001) with the greatest metabolic cost resulting from foot loading. Although vertical load position influences the metabolic cost of walking, it does not affect the mechanics of walking. These results suggest that other factors such as the cost of leg swing may explain the greater metabolic cost of lower body loading.