The relationship between extremes of resting metabolic rate and mechanical efficiency

Whether differences in energy metabolism, as manifested in resting metabolic rates, influence exercise metabolism raises important questions concerning energy balance in individuals. To address this issue, the relationship between extremes of resting metabolic rate and mechanical efficiency of cycle ergometer and treadmill exercise was investigated. Five subjects with high resting metabolic rates (1.20 ± 0.03 kcal/kg/hr) and six subjects with low resting metabolic rates (0.78 ± 0.01 kcal/kg/hr) participated in the study. Delta and gross efficiencies were calculated from the exercise response of the subjects during work on a cycle ergometer at work rates of 150, 300, and 450 kgm/min and on a treadmill at 80.4 mpm with grades of 3, 6, and 9%. Analysis of repeated measures revealed no significant differences for delta and gross efficiencies of the two groups on both the cycle ergometer and the treadmill. As an artifact of the calculation of gross efficiency, the extreme difference between the resting metabolic rates of the two groups resulted in a significant difference in the gross efficiency measurements at the initial intensity on the treadmill. It was concluded that mechanical efficiency is not influenced by extremes of resting metabolic rate and exercise remains an important component of the energy balance equation.