This study investigated the effect of acute full-body resistance exercise [RE; one set of 10 repetitions at 40% 1 repetition maximum (1RM) and three sets of 10 repetitions at 65% 1RM] on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and whole body substrate oxidation in young (age: 22 ± 1 yr), normal-weight and body fatness (body mass index: 20 ± 1 kg/m2; %body fat: 28.7 ± 1.4%), resistance-trained women. Microdialysis was used to measure SCAAT lipolysis at baseline, mid-RE, post-RE, and 30 min post-RE, and indirect calorimetry was used to measure whole body substrate oxidation at baseline and immediately post-RE in 13 women. Plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFA), glycerol, growth hormone (GH), epinephrine (Epi), and norepinephrine (NE) were measured at baseline, mid-RE, and post-RE. Lipolysis (dialysate glycerol concentration) was elevated post-RE (baseline: 596.7 ± 82.8, post-RE: 961.4 ± 116.3 µM, P = 0.01). Energy expenditure (baseline: 1,560 ± 49; post-RE: 1,756 ± 68 kcal/day; P = 0.02) and fat oxidation (baseline: 5.64 ± 0.24; post-RE: 7.57 ± 0.41 g/h; P = 0.0003) were elevated post-RE. GH (baseline: 513.1 ± 147.4; mid-RE: 1,288.3 ± 83.9; post-RE: 1,522.8 ± 51.1 pg/ml, P = 0.000), Epi (baseline: 23.2 ± 2.7; mid-RE: 92.5 ± 16.6; post-RE: 84.5 ± 21.4 pg/ml, P = 0.000), and NE (baseline: 139.2 ± 13.6; mid-RE: 850.9 ± 155.3; post-RE: 695.3 ± 93.5 pg/ml, P = 0.000) were higher at mid-RE and post-RE. Therefore, one of the potential mechanisms behind RE-induced fat mass changes in resistance-trained women may be in part due to the accumulated effect of transient increases in SCAAT lipolysis, fat oxidation, and energy expenditure, mediated by GH, Epi, and NE release.
Keywords: fat oxidation; growth hormone; lipolysis; resistance exercise; resting metabolic rate.