Mechanical energy analyses of the human during load carriage on a treadmill

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Abstract
Variations of the mechanical energy levels of the body segments, as affected by different backpack loads were investigated, to determine if mechanical energy analyses rather than metabolic measures could be used to evaluate load carriage devices. Six male subjects were required to walk upon a level treadmill at 5.54 km/h while they carried 5 loads ranging 15.16-33.85 kg, in a specially designed backpack. Cinefilm was taken, digitized and filtered. Kinematic data, energy levels of the segments of a 15 member linked-segment model and overall work indices were calculated. Expired air was collected and metabolic cost determined. About 1/3 of the mechanical work done by all body segments represents energy exchanges within segments and another 1/3 between segments; the major increase in the mechanical work done was in the load itself and virtually no alternations in gait pattern were made by the subjects to accommodate heavier loads. Some undesirable exchanges of energy were evident between the backpack and the trunk. The mechanical assessments apparently were sufficiently sensitive and detailed to evaluate backpacks and provided information not available from metabolic analysis alone. Some diagnostic information which could prove useful for the redesign of the load carriage device emerged from the body segment mechanical energy curves.