Oxygen Consumption and Substrate Utilization During and After Resistance Exercises Performed with Different Muscle Mass

This study investigated the energy expenditure (EE) and substrate utilization reflected by the respiratory-exchange ratio (RER) during and after resistance exercises performed with different muscle mass. Ten male volunteers (mean±SD; 26±4yr, 179±6cm, 77±8kg) performed multiple sets of the horizontal leg press (LP) and chest fly (CF) (5 sets of 10 repetitions with 15 repetition-maximum, 1-minute between-set intervals) in a counterbalanced design. Oxygen uptake and carbon dioxide production were measured during 40 minutes of resting; resistance exercise protocols (sets and intervals); 90 minutes of post-exercise recovery. Total fat and carbohydrate oxidation rates were calculated according to the non-protein respiratory quotient. Both exercise conditions elicited net excess post-exercise oxygen consumption (EPOC) of similar duration (approximately 40min). The EPOC magnitude at 40 minutes was greater after LP than after CF (7.36±1.10L vs. 4.73±0.99L; P<0.001). The RER was higher in LP (1.30±0.04) than CF (1.16±0.05, P=0.0003) during exercise. During recovery the RER was similar in LP and CF (P>0.05) and lower than pre-exercise (Pre-exercise=0.78±0.04 vs. CF40min=0.74±0.04; CF90min=0.68±0.02 and LP50min=0.73±0.06; LP90min=0.65±0.04, P<0.05). However, fat oxidation after LP was greater than CF between 30-90 minutes of recovery (mean total fat oxidation: LP=10.9 g vs. CF=8.4 g; P<0.01). The increases of EE and fat oxidation during post-exercise recovery were greater after multiple sets of resistance exercises performed with larger muscle mass than smaller muscle mass. This finding has practical implications for resistance training designed as part of weight management programs.