Relationship between maximum aerobic power and resting metabolic rate in young adult women

The literature is inconclusive as to the chronic effect of aerobic exercise on resting metabolic rate (RMR), and furthermore there is a scarcity of data on young women. Thirty-four young women exhibiting a wide range of aerobic fitness [maximum aerobic power (V̇O(2max)) = 32.3-64.8 ml · kg^-1 · min^-1] were accordingly measured for RMR by the Douglas bag method, treadmill V̇O(2max), and fat-free mass (FFM) by using Siri's three- compartment model. The interclass correlation (n = 34) between RMR (kJ/h) and V̇O(2max) (ml · kg^-1 · min^-1) was significant (r = 0.39, P < 0.05). However, this relationship lost statistical significance when RMR was indexed to FFM and when partial correlation analysis was used to control for FFM differences. Furthermore, multiple linear-regression analysis indicated that only FFM emerged as a significant predictor of RMR (kJ/h). When high- (n = 12) and low-fitness (n = 12) groups were extracted from the cohort on the basis of V̇O(2max) scores, independent t-tests revealed significant between- group differences (P < 0.05) for RMR (kJ · kg^-1 · h^-1) and V̇O(2max) (ml · kg^-1 · min^-1) but not for RMR (kJ/h), RMR (kJ · kg FFM^-1 · h^-1), and FFM. Analysis of covariance of RMR (kJ/h) with FFM as the covariate also showed no significant difference (P = 0.56) between high- and low-fitness groups. Thus the results suggest that 1) FFM accounts for most of the differences in RMR between subjects of varying V̇O(2max) values and 2) the RMR per unit of FFM in young healthy women is unrelated to V̇O(2max).