Failure of prior low-intensity exercise to potentiate the thermic effect of glucose

Summary

We have previously shown that following recovery from 45 min exercise at 67% maximum oxygen consumption$\left( {\dot V_{E max} } \right)$ the thermic effect of a glucose load is increased by 65% over that observed on a non-exercise day (Young et al. 1986). The purpose of this study was to determine if potentiation of the thermic effect of glucose by prior exercise is dependent on exercise intensity. The thermic response to a 1674 kJ glucose load was measured in five subjects in the absence of exercise (control) and following recovery from 45 min cycling exercise at each of three intensities: low (34%$\dot VO_{2 max}$), moderate (54%$\dot VO_{2 max}$), and high (75%$\dot VO_{2 max}$). The average percentage increase in oxygen consumption over baseline due to glucose ingestion was similar for the control (9.9%, SE 2.0%), and the low- (10.2%, SE 0.9%) and moderate- (12.6%, SE 1.2%) intensity exercise conditions, while a significant increase in average$\dot VO_{2 max}$ was observed after the high-intensity condition (18.0%, SE 2.3%,P < 0.05). The total energy expenditure (kJ) over baseline for 3 h was also similar for the control (84.5, SE 11.7), and the low-(100.0, SE 9.2) and moderate- (118.8, SE 5.0) intensity exercise conditions. The thermic response following high-intensity exercise (146.4 kJ, SE 13.4) was significantly greater than that observed in the control (P < 0.01) or low-intensity (P < 0.05) exercise conditions. These findings demonstrate that unlike prior high-intensity exercise (75%$\dot VO_{2 max}$), low- or moderate-intensity exercise (i.e., 34% or 54%$\dot VO_{2 max}$) fails to potentiate the thermic effect of a glucose load. The results of this and our previous study suggest that prior exercise must be of sufficient intensity, i.e., greater than approximately 60%$\dot VO_{2 max}$, in order to positively affect meal-induced thermogenesis.