Effects of exercise training on resting metabolic rate - discrepancies and standardization of experimental design -

Effects of exercise training on resting metabolic rate - discrepancies and standardization of experimental design -

  Resting metabolic rate (RMR) is the minimum energy expenditure necessary for maintenance of critical body function. Although many scientists have attempted to investigate the effects of exercise training on RMR, these studies have produced contradictory results. Several methodological discrepancies, which may account for the contradictory results, were found among these studies. This study was designed to examine the methodological discrepancies and to suggest the standard research design in this area. The cross-sectional studies were limited by several confounding variables such as: 1) within subject variability due to preceding nutritional status and dietary practices, and 2) failure to control the physical training regimen priorto RMR measurements. Additionally, the cross-sectional studies, which examine the RMR of individuals who have various levels of VO2max and consider the difference in RMR as a result of exercise training, need to account or control for other factors, e.g., genetic variations. Several methodological discrepancies which have been suggested frequently in the prospective studies include 1) elapsed time between the last exercise session and the measurement of RMR; 2) methodological errors in indirect calorimetry measurements; 3) insufficient sample size; 4) inconsistency in the units of expressing RMR; 5) differences in age of subjects; 6) initial fitness level of subjects; and 7) training mode. In adddition, the mechanism(s) for the change in RMR with exercise training were not investigated in many studies. To standardize the research design and/or experimental procedures, the followings can be suggested: 1) Prospective studies including control group should be designed; 2) At least 24 ? 36 hours should elapse from the last exercise session to RMR measurement and the RMR should be measured longer than 45 min; 3) Inter-test and inter-technician reliability of the indirect calorimetry should be confirmed; 4) A power analysis should be conducted to include sufficient number of subjects; 5) The results of RMR should be expressed in various units for the purpose of comparison with the results of previous studies; 6) Intensity of exercise training should be high enough to induce a chronic elevation in RMR; 7) The mechanisms for the change in RMR with the exercise training should be investigated in integrated manner.