Cardio-respiratory performance of porters carrying loads on a treadmill

Abstract

Four workers, accustomed to load carrying, carried loads (no load, 60, 80 and 100 kg) at 0·89 and 1·03 m s−1 on a treadmill during the pre- and post-lunch period respectively, to obtain information regarding the degree of exhaustion from similar load carrying in their usual working situation. The rate of work is expressed in Watts. During pre- and post-lunch work there was a rise of 6 to 71 of pulmonary ventilation with each increment of 163 W. beyond the initial work level. The oxygen consumptions in the pre-lunch period were 15 to 27% higher, suggesting a greater anaerobic metabolism in the post-lunch period. The average work-pulse-rate varied from 116 to 162 beats min−. Cardiac demand for a particular load is more or less constant, irrespective of time of day. During the pre-lunch period the work-pulse-sum was 78, 71, 65 and 54 beats per 163 W for respective four loads;-where-as in the post-lunch period, except the initial load, it varied only between 56 to 60 beats per 163 W. indicating a proportionate rise of pulse beats during post-lunch work. The 1st, 2nd and 3rd min recovery pulses of the 3rd and 4th loads were much beyond a level sustainable throughout the day. The recovery-pulse-sum varied from 39 to 104 beats and 36 to 117 beats min− during the pre- and post-lunch period respectively, which were mostly beyond the permissible endurance limit. The oxygen-pulse for similar loads were 18 to 44% higher in the pre-lunch period, indicating better ability to work. To arrive at a reasonable load and rate of work, simple and multiple regression equations have been evolved. Indian workers may be allowed to work up to 1140 W (i.e. 50 to 55% of maximum oxygen uptake).