ENERGY-METABOLISM IN SEDENTARY AND ACTIVE 49-YR-OLD TO 70-YR-OLD WOMEN

This study examined differences between long-term exercising (LE) and long-term nonexercising (LNE) women [n = 24; age 56.4 +/- 6.2 (SD) yr] for resting metabolic rate (RMR) and energy expenditure in the free-l iving state by using doubly labeled water (DL). There was a statistica lly significant difference (P = 0.0002) between the 12 LE (94.85 +/- 8 .44 kJ.kg(-1).day(-1)) and 12 LNE (81.16 +/- 6.62 kJ.kg(-1).day(-1)) f or RMR, but this difference was only marginally significant (P = 0.06) when the data (MJ/day) were subjected to an analysis of covariance wi th fat-free mass as the covariate. The DLW data indicated that the eig ht most active LE (12.99 +/- 3.58 MJ/day) expended significantly (P = 0.01) more energy than did the eight least active LNE (9.30 +/- 1.15 M J/day). Energy expenditures ranged from 7.64 to 18.15 MJ/day, but ther e was no difference (P = 0.96) between the LE and LNE in energy expend iture during activity that was not designed to either improve or maint ain fitness. These cross-sectional data on 49- to 70-yr-old women ther efore suggest that I) aerobic-type training results in a greater RMR p er unit of body mass and also when statistical control is exerted for the effect of the metabolically active fat-free mass, 2) there is a la rge range in the energy intake necessary to maintain energy balance, a nd 3) aerobic training does not result in a compensatory reduction in energy expenditure during the remainder of the day.