Transfers of mechanical energy within the total body and mechanical efficiency during treadmill walking

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Abstract
The efficiency of human gait has been the subject of comment and speculation for some time. Biomechanically it has been shown that there are passive energy exchanges within body segments and between adjacent segments. The purposes of this paper were to measure and calculate how much of the segment energy changes can be attributed to muscular activity versus these passive exchange mechanisms, and to calculate the mechanical efficiency of overground walking based on the internal mechanical work. Six male subjects, matched for age, height and weight, were analysed during level treadmill walking at an average velocity of 1-54 -1 and a step length of 0-79m using an 11 segment planar biomechanical model. It was determined that the rate of doing internal work, both positive and negative, was about 165 W although the total observed work rate was 500 W. The rate of passive energy exchange within and between segments was 335 W. These results indicate that about two-thirds of the observed mechanical energy changes are conserved in normal gait, with muscle activity accounting for only one-third of these energy changes. Based on the internal mechanical work and metabolic measures the net mechanical efficiency was calculated to be 65% Assuming that negative work was three times as efficient as positive work the efficiencies were calculated to be 130% and 43.3% respectively.