ENERGY-EXPENDITURE AND SUBSTRATE UTILIZATION IN OLDER WOMEN AFTER STRENGTH TRAINING - 24-H CALORIMETER RESULTS

The purpose of this study was to examine the effects of strength train ing (ST) in healthy older women on 24-h energy expenditure (EE) and it s components and on 24-h substrate utilization. Thirteen women (age 67 +/- 1 yr) exercised three times per week for 16 wk in a total body ST program. EE components and substrate utilization were determined for 24 h in an indirect room calorimeter before and after training. The ST invoked a 47% increase in upper body and a 66% increase in lower body strength (P < 0.001). Body weight, percent body fat, and fat-free mas s did not change significantly; however, midthigh muscle area increase d (55.2 +/- 3.1 vs. 60.4 +/- 2.3 cm(2); P < 0.05). There was a signifi cant increase in resting EE (5,017 +/- 218 vs. 5,473 +/- 213 kJ/day; P < 0.05) but no significant changes in sleeping EE (4,929 +/- 180 vs. 5,067 +/- 251 kJ/day), diet-induced thermogenesis (359 +/- 25 vs. 393 +/- 33 kJ/day), activity EE (682 +/- 84 vs. 381 +/- 117 kJ/day), or 24 -h EE (6,054 +/- 188 vs. 6,247 +/- 243 kJ/day). The increase in restin g EE was not significant after the increase in muscle area is taken in to account. The 24-h nonprotein respiratory quotient decreased (0.90 /- 0.01 vs. 0.82 +/- 0.01; P < 0.001), revealing a significant increas e in 24-h fat oxidation (42 +/- 6 vs. 81 +/- 7 g/day) and a decrease i n carbohydrate oxidation (180 +/- 14 vs. 113 +/- 10 g/day; both P < 0. 001). In conclusion, ST increases resting EE and fat oxidation, which may have important implications in improving the metabolic profile of older adults. The increase in resting EE may be partly explained by in creased muscle mass.