Effect of 3 weeks of detraining on the resting metabolic rate and body composition of trained males

Objective: To examine the hypothesis that detraining decreases the resting metabolic rate (RMR) of long-term exercisers. Design: Eight pairs of subjects were matched for age, mass and training volume. They were then randomly allocated to either a control group (continue normal training) or detraining group (stop normal training but continue activities of daily living). Setting: Exercise Physiology Laboratory, The Flinders University of South Australia. Subjects: Sixteen male subjects (age 23.1 ± 4.7 y (s.d.); mass 73.73 ± 8.9 kg; V̇O(2max) 60.2 ± 6.3 ml. kg -1 .min -1 ; height 180.3 ± 5.0 cm; body fat 14.6 ± 5.4%) were selected from a pool of respondents to our advertisements. Interventions: Each pair of subjects was measured before and after a 3-week experimental period. Results: Two (groups) x 3 (2-, 3-and 4-compartment body composition models) ANOVAs were conducted on the difference between the pre- and post-treatment scores for percentage body fat, fat-free mass (FFM) and relative RMR (kJ.kg FFM -1 .h -1 ). No significant between-group differences were identified except for the detraining group's small decrease in FFM (0.7 kg, P = 0.05). The main effects for body composition model were all significant; but the overall differences between the multicompartment models and the 2-compartment one were less than their technical errors of measurement. No significant interaction (P = 0.51) resulted from a 2 x 2 ANOVA on the pre- and post-treatment absolute RMR data for the control (315.2 and 311.9 kJ/h) and detraining groups (325.4 and 325.5 kJ/h). Conclusions: 3-weeks detraining is not associated with a decrease in RMR (kJ/h, kJ.kg FFM -1 .h -1 ) in trained males; hence, our data do not support a potentiation of the RMR via exercise training. The greater sensitivity of the multicompartment models to detect changes in body composition was of marginal value. Sponsorship: Australian Research Council.