Efficiency of trained subjects differing in maximal oxygen uptake and type of training

This study was undertaken to examine the relationship between energy expenditure and work rate on a bicycle ergometer in five sprinters and five distance runners who differed in maximal oxygen uptake (VO2max) and type of training. Each subject performed at work rates of 30, 60, 90, 120, and 150 watts (W). The relationship between energy expenditure and work rates was most accurately described by a quadratic curve for both groups: for sprinters, energy expenditure (kJ) = 11.57 + 0.1812 (W) + 0.00046 (W)2; for distance runners, energy expenditure (kJ) = 11.74 + 0.1386 (W) + 0.00060 (W)2. Delta efficiency (delta work accomplished divided by delta energy expended X 100%) decreased as work rate increased. Statistical analyses revealed no significant differences between groups in delta efficiency at the same work rate (P greater than 0.25) or at the same relative work rate (P greater than 0.75). These results suggest that differences in VO2max and/or type of training have little or no causal effect on the decrease in delta efficiency with increasing work rate. The observed decrease in delta efficiency may be due to increases in metabolism not directly related to the performance of the external work or to an increasing amount of unmeasured work as work rate increases on a bicycle ergometer.