20:T43c,This study examined gender differences in resting metabolic rate (RMR) across a broad age spectrum after controlling for differences in body composition and aerobic fitness. Three hundred twenty-eight healthy men (17-80 yr) and 194 women (18-81 yr) volunteers were characterized for RMR, body composition, physical activity, peak oxygen consumption (peak VO2), anthropometrics, and energy intake. Measured RMR was 23% higher (P < 0.01) in men (1,740 +/- 194 kcal/day) than in women (1,348 +/- 125 kcal/day). Multiple regression analysis showed that 84% of individual variation in RMR was explained by fat-free mass, fat mass, peak VO2, and gender. After controlling for differences in fat-free mass, fat mass, and peak VO2, a lower RMR (3%; P < 0.01) persisted in women (1,563 +/- 153 kcal/day) compared with men (1,613 +/- 127 kcal/day). Adjusted RMR in premenopausal (P < 0.01) and postmenopausal (P < 0.05) women was lower than in men of a similar age. Our results support a lower RMR in women than in men that is independent of differences in body composition and aerobic fitness.21:T535,Resting metabolic rate (RMR) decreases with age, largely because of an age-related decline in fat-free mass (FFM). We hypothesized that a strength-training program capable of eliciting increases in FFM would also increase RMR in older individuals. To test this hypothesis, RMR, body composition, and plasma concentrations of certain hormones known to affect RMR were measured before and after a 16-wk heavy-resistance strength-training program in 13 healthy men 50-65 yr of age. Average strength levels, assessed by the three-repetition maximum test, increased 40% with training (P < 0.001). Body weight did not change, but body fat decreased (25.6 +/- 1.5 vs. 23.7 +/- 1.7%; P < 0.001) and FFM increased (60.6 +/- 2.2 vs. 62.2 +/- 2.1 kg; P < 0.01). RMR, measured by indirect calorimetry, increased 7.7% with strength training (6,449 +/- 217 vs. 6,998 +/- 226 kJ/24 h; P < 0.01). This increase remained significant even when RMR was expressed per kilogram of FFM. Strength training increased arterialized plasma norepinephrine levels 36% (1.1 +/- 0.1 vs. 1.5 +/- 0.1 nmol/l; P < 0.01) but did not change fasting glucose, insulin, or thyroid hormone levels. These results indicate that a heavy-resistance strength-training program increases RMR in healthy older men, perhaps by increasing FFM and sympathetic nervous system activity.22:T54a,The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39 +/- 8%; P < 0.001) and lower (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) increased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and total fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg; P < 0.01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0.001) were observed. When measured by DEXA, FFM was increased in the arms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in the arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.143 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training.(ABSTRACT TRUNCATED AT 250 WORDS)23:T505,In our study of 125 subjects (53 men and 72 women) for two 24-h periods, we validated energy expenditure (EE), estimated by a triaxial accelerometer (Tritrac-R3D), by using a whole-room indirect calorimeter under close-to-normal living conditions. The estimated EE was correlated with the meas

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