Effect of an 18-wk weight-training program on energy expenditure and physical activity

Department of Human Biology, University of Limburg, Maastricht, The Netherlands. The purpose of this study was to examine the effect of an 18-wk weight-training program on average daily metabolic rate (ADMR). Before the intervention and in weeks 8 and 18 (T0, T8, and T18, respectively) data on body composition, sleeping metabolic rate (SMR), food intake, energy cost of the weight-training program (EEex), and nontraining physical activity (accelerometer) were collected in the exercise group (EXER, n = 18 males). ADMR was determined in a subgroup (EX12, n = 12) by using doubly labeled water. At T0 and T18, data (except ADMR) were also collected in a control group (Con, n = 8). Body mass did not change in EXER or Con. Fat-free mass increased only in EXER with 2.1 +/- 1.2 kg, whereas fat mass decreased in EXER as well as Con (2.0 +/- 1.8 and 1.4 +/- 1.0 kg, respectively). Initial ADMR (12.4 +/- 1.2 MJ/day) increased at T8 (13.5 +/- 1.3 MJ/day, P < 0.001) with no further increase at T18 (13.5 +/- 1.9 MJ/day). SMR did not change in EXER (4.8 +/- 0.5, 4.9 +/- 0.5, 4.8 +/- 0.5 kJ/min) or Con (4.7 +/- 0.4, 4.8 +/- 0.4 kJ/min). Energy intake did not change in EXER (10.1 +/- 1.8, 9.7 +/- 1.8, 9.2 +/- 1.9 MJ/day) or Con (10.2 +/- 2.6, 9.4 +/- 1.8, 10.1 +/- 1.5 MJ/day) and was systematically underreported in EX12 (-21 +/- 14, -28 +/- 18, -34 +/- 14%, P < 0.001). EEex (0.47 +/- 0.20, 0.50 +/- 0.18 MJ/day) could only explain 40% of the increase in ADMR. Nontraining physical activity did not change in both groups. In conclusion, although of modest energy cost, weight-training induces a significant increase in ADMR