Abstract
From a series of experiments on nine human volunteers carrying different loads on the head up a flight of stairs at a fixed rate of ascent, it has been shown that the energy cost (E) is linearly related (r=0.97) to the gross weight carried, namely the sum of the weight of the individual (W) and the external load (L), according to E (kcal/min) =0.0737(W+L) (kg) +0.0413. The peak heart rate (PHR) attained by the subject also showed a linear correlation (r=0.88) with the gross weight PHR(no/min) =1.33(W+L) (kg) +53.69. These regressions are highly significant statistically. It has been demonstrated that, it is possible to predict from these regressions with consider-able accuracy the energy cost and peak heart rate for such muscular work for a similar group of human subjects carrying similar loads by independent tests on six subjects.
The mechanical efficiency of this physical task has been computed in each case. The gross efficiency and the net efficiency i.e., the external work performed as percent-ages of the gross and net energy costs (gross energy cost minus energy cost at rest) are remarkably consistent for the different subjects, with mean value and net efficien-cies respectively. A concept termed "Work Pulse", being the external work performed in kilogram meters per heart beat, has been proposed as a practical measure of efficien-cy. The value of this simple index for studying the work stress-strain relationship has been discussed.
