Metabolic Responses to Exercise AEROBIC AND ANAEROBIC CONTRIBUTIONS TO NON- STEADY STATE ENERGY EXPANDITURE DURING STEADY STATE POWER OUTPUT

Scott CB, Shaw B, Leonard C. Aerobic and Anaerobic Contributions to Non-Steady State Energy Expenditure during Steady State Power Output. JEPonline 2008;11(2):56-63. We estimated aerobic and anaerobic energy expenditure during and after a 6-min intense steadystate workload that is typically modeled using oxygen-only measurements; gender comparisons were made. Maximal testing revealed peak oxygen uptake was not different between men (N = 8) (46.5 ± 8.0 ml kg min) and women (N = 8) (42.6 ± 7.5 ml kg min) (p = 0.34). Subjects later cycled for 6-min at a similar physiological intensity based on the maximal test results. Perceived exertion for the 6-min ride was similar between men, 18.1 ± 1.7 and women, 18.1 ± 2.4 (p = 0.80). However, power output for the 6-min ride was greater in men (203 ± 23 Watts) as compared to women (145 ± 34 Watts) (p = 0.001). Pooled data (men and women) revealed exercise energy expenditure was significantly greater when containing an anaerobic component (271.2 ± 66.1 kJ vs 328.0 ± 74.5 kJ; p < 0.03); this also was true for menbut not women-only data. Relative energy expenditure contributions for exercise and recovery were similar for men and women: anaerobic exercise, 1314%; aerobic exercise, 65%; aerobic recovery, 21-22%. We conclude that gender comparisons regarding the extent of aerobic and anaerobic contributions to energy expenditure can be confounded by the method of interpretation (absolute and relative data analyses). Estimates of anaerobic energy expenditure throughout 6-min of intense exercise exceeds that of the slow O2 component that occurs for the last 3-min of exercise.