Energy expenditure while standing or walking slowly uphill or downhill with loads

Abstract

Eight fit male subjects (24 yr, 176 cm, 79 kg) stood, or walked at speeds of 0·5 or 0·9 m s−1 for 20-min periods on grades of − 10 to + 25% with loads of 20 or 40 kg. Energy expenditure (watt) was not significantly different in any of the standing conditions; grade and load increased energy expenditure while standing but not significantly. Although all the standing energy expenditure means were relatively low, high perceived exertion ratings suggest limits to tolerance time in some of these conditions. All the standing means were significantly lower than the walking means. Walking 0·9 m s−1 on a −10% grade was significantly lower than walking 0·5 m s−1 on a + 10% grade, which was significantly lower than walking 0·9 m s−1 on a + 10% grade. In the walking conditions there was a significant difference between loads: means for the 20 kg loads were lower than means for the 40 kg loads. As the condition became more strenuous by increasing load, speed, and/or grade (while walking), energy expenditure became more sensitive to changes in these variables. The current energy expenditure prediction formula (Pandolf et al. 1977) was found to predict slightly high for the standing conditions, low for walking 0·5 m s−1 on a + 10% grade, and accurately for walking 0.9 m s−1 on a + 10% grade. In the standing conditions the deviation between predicted and measured was higher at the 40 kg load than at the 20 kg load. The formula in its present form is not equipped to predict for negative grades. The results of this study suggest that the prediction formula may place too much emphasis on the effects of speed and load while standing and walking slowly.