Work of Carrying Loads

Abstract

Transportation of loads is one of the commonest activities of men. In spite of this, the literature indicates that load carrying has received little scientific study. The measures generally used to indicate load carrying efficiency have been pulse rate, oxygen consumption and calories expended per distance or per unit time. A recent innovation has been the use of field tests which measure the time required for S to carry a load over a prescribed course. Although physiological indicators taken with S walking on a treadmill provide wellcontrolled data, field studies give a more realistic estimate of the effect of various loadings. The optimum load weight has been found to be approximately 35% of body weighc: the optimum rate of carry, 85-95 yd/min. Faster rates of carrying result in greater energy expenditure than do increasing weights of loads up to 41% of body weight. The best position is the one which least affects the carrier's balance and center of gravity. This will vary with the weight of the load; high positions are better for loads under 46 Ib., low positions better for heavier loads. The shape of the load affects both the balance and the center of gravity of the carrier. Clothing, physical condition of the Ss and training in specific techniques of carrying are all influential in determining the efficiency of load carrying and should be controlled in future experiments. Further study is needed to clarify the differences obtained berween physiological measures of ef6ciency and subjective preferences for daerenc types of loads. Finally, it is suggested that studies be made to determine the effect of load carrying on performance after carrying the loads. In practical situations it is often as important to obtain near optimum performance from the man after he has put the load down as it is to improve the efficiency of the load carrying performance itself.