Aerobic fitness, physiologic difficulty and physical activity in Black and White women.

PURPOSE: The purpose of this work was to determine if racial differences in maximum oxygen uptake (VO(2) max) and difficulty in doing submaximum (sub) exercise tasks contribute to activity-related energy expenditure (AEE) and activity-related time equivalent (ARTE) index, an index of time spent in physical activity. METHODS: Subjects were 35 Black and 39 White sedentary premenopausal women group matched for age, weight and body composition. Percent fat was determined by dual energy X-ray absorptiometry, AEE by doubly labeled water and sleeping energy expenditure, ARTE index by AEE and energy cost above sleeping for five exercise tasks, and VO(2) max by a graded exercise test. Subexercise oxygen uptake was measured during walking at 3 mph on the flat and up a 2.5% grade, climbing stairs, and riding a bike ergometer at 50 W. Difficulty of exercise was assessed during the subexercise and taken as heart rate, ventilation, and ratings of perceived exertion (RPE) and expressed as a % of the individual's maximum. RESULTS: VO(2) max was related to AEE (r=0.29, P<0.04) and to ARTE index (r=0.37, P<0.01). All three difficulty measures were related to AEE (r=-0.35 to -0.42, P-values<0.02) and the ARTE index (r=-0.49 to -0.52, all P-values<0.01), with the exception of RPE with ARTE (r=-0.27, P=0.10). Compared to Black women, White women had significantly higher VO(2) max (12%), AEE (45%) and ARTE (50%), and significantly less physiologic difficulty of performing the subexercise tasks: heart rate (5%), ventilation (13%), and RPE (8%). Significant racial differences in AEE and ARTE disappeared after adjusting for any of the three difficulty measures. CONCLUSIONS: These results show that more participation in free-living physical activity is related to greater VO(2) max and less difficulty in being active. In addition, lower levels of physical activity found in Black women may be partially explained by lower VO(2) max and increased difficulty of engaging in physical activities.

High-resistance versus variable-resistance training in older adults.

PURPOSE: The purpose of this study was to compare the effects of high-resistance (HR) training, 3 times.wk(-1) at 80% maximum strength (1RM) with 3 times.wk(-1) variable-resistance (VR) training (once-weekly training at 80%, 65%, and 50% 1RM) in older adults. METHODS: The study was a 6-month resistance training intervention conducted in the Birmingham Alabama metropolitan area, and included healthy volunteer men and women over the age of 60. Twenty-eight subjects were assigned randomly to two training groups. Eight volunteers served as controls. Before and after 25 wk of training, body composition was measured by densitometry; strength by isometric tests; and difficulty in performing daily activity tasks (DAT) by measuring heart rate, oxygen uptake, electromyography, and perceived exertion. In addition, 1RM strength was measured every 25 d throughout the 6 months of training. Repeated measures ANOVA and paired t-tests with Bonferroni corrections for additive alpha were used to analyze the data. RESULTS: The control group did not significantly change in any study parameter. No significant change in body weight occurred for any group. However, the HR and VR groups increased fat free mass (FFM) similarly (1.8 kg and 1.9 kg, respectively). Both training groups increased strength significantly, without significant differences in change. No significant change in oxygen uptake occurred during DAT. However, there was a significant time effect for heart rate and perceived exertion. Greater decrease in normalized integrated electromyography during the carry task was found in the VR group over the HR and control groups. CONCLUSION: Despite similar increases in strength and fat free mass, the VR group decreased difficulty of performing the carry task more than the HR group. These data suggest that larger improvements in DAT may be achieved if frequency of high-resistance training is less than 3 times.wk(-1).

Body fat distribution in white and black women: different patterns of intraabdominal and subcutaneous abdominal adipose tissue utilization with weight loss.

BACKGROUND: Intraabdominal adipose tissue (IAAT) is the body fat depot most strongly related to disease risk. Weight reduction is advocated for overweight people to reduce total body fat and IAAT, although little is known about the effect of weight loss on abdominal fat distribution in different races. OBJECTIVE: We compared the effects of diet-induced weight loss on changes in abdominal fat distribution in white and black women. DESIGN: We studied 23 white and 23 black women, similar in age and body composition, in the overweight state [mean body mass index (BMI; in kg/m(2)): 28.8] and the normal-weight state (mean BMI: 24.0) and 38 never-overweight control women (mean BMI: 23.4). We measured total body fat by using a 4-compartment model, trunk fat by using dual-energy X-ray absorptiometry, and cross-sectional areas of IAAT (at the fourth and fifth lumbar vertebrae) and subcutaneous abdominal adipose tissue (SAAT) by using computed tomography. RESULTS: Weight loss was similar in white and black women (13.1 and 12.6 kg, respectively), as were losses of total fat, trunk fat, and waist circumference. However, white women lost more IAAT (P < 0.001) and less SAAT (P < 0.03) than did black women. Fat patterns regressed toward those of their respective control groups. Changes in waist circumference correlated with changes in IAAT in white women (r = 0.54, P < 0.05) but not in black women (r = 0.19, NS). CONCLUSIONS: Despite comparable decreases in total and trunk fat, white women lost more IAAT and less SAAT than did black women. Waist circumference was not a suitable surrogate marker for tracking changes in the visceral fat compartment in black women.

Energy expenditure and free-living physical activity in black and white women: comparison before and after weight loss.

BACKGROUND: The prevalence of obesity is higher in black than in white women. Differences in energy economy and physical activity may contribute to this difference. OBJECTIVE: The objective of this study was to compare free-living energy expenditure and physical activity in black and white women before and after weight loss. DESIGN: Participants were 18 white and 14 black women with body mass indexes (in kg/m(2)) between 27 and 30. Diet, without exercise, was used to achieve a weight loss of >/=10 kg and a body mass index <25. After 4 wk of energy balance in overweight and normal-weight states, body composition was assessed by using a 4-compartment model, sleeping and resting energy expenditures were assessed by using a chamber calorimeter, physiologic stress of exercise and exercise economy were measured by using standardized exercise tasks, and daily energy expenditure was assessed by using doubly labeled water. RESULTS: Weight loss averaged 12.8 kg. Sleeping and resting energy expenditures decreased in proportion to changes in body composition. Weight reduction significantly improved physiologic capacity for exercise in both groups of women, making it easier for them to be physically active. Black women had lower body composition-adjusted energy requirements than did white women-both before and after weight loss-during sleep (9% lower, 519 kJ/d; P < 0.001), at rest (14% lower, 879 kJ/d; P < 0.001), during exercise (6% lower; P < 0. 05), and as a daily total (9% lower, 862 kJ/d; P < 0.06). By contrast, free-living physical activity was similar between the groups. CONCLUSIONS: Weight-reduced women had metabolic rates appropriate for their body sizes. Black women had lower resting and nonresting energy requirements in both overweight and normal-weight states than did white women and did not compensate with greater physical activity, potentially predisposing them to greater weight regain.

Racial differences in energy expenditure and aerobic fitness in premenopausal women.

BACKGROUND: Aerobic fitness, or maximal oxygen uptake (f1.gif" BORDER="0">O(2)max), and energy expenditure (EE) may be lower in African Americans than in whites. OBJECTIVE: The objective of this study was to compare sleeping EE (SEE), resting EE (REE), free-living total EE (TEE), and f1.gif" BORDER="0">O(2)max in African American and white women after adjustment for body composition and free-living activity-related energy expenditure (AEE). DESIGN: Eighteen African American and 17 white premenopausal women were matched for weight, percentage body fat, and age. SEE and REE were measured in a room calorimeter and f1.gif" BORDER="0">O(2)max was measured on a treadmill. Fat-free mass (FFM) and fat mass (FM) (4-compartment model), AEE (doubly labeled water and SEE), and regional lean tissue (dual-energy X-ray absorptiometry) were used as adjustment variables in SEE, REE, TEE, and f1.gif" BORDER="0">O(2)max comparisons. RESULTS: The African American women had significantly more limb lean tissue and significantly less trunk lean tissue than did the white women. The African American women also had significantly lower SEE (6.9%), REE (7.5%), TEE (9.6%), and f1.gif" BORDER="0">O(2)max (13.4%) than did the white women. Racial differences persisted after adjustment for f1.gif" BORDER="0">O(2)max, AEE, FFM, and limb lean tissue but disappeared after adjustment for trunk lean tissue. The f1.gif" BORDER="0">O(2)max difference was independent of all body-composition variables and of AEE. CONCLUSIONS: African American women had lower aerobic fitness than did white women, independent of differences in lean tissue or AEE. Diminished racial differences in SEE, REE, and TEE after adjustment for trunk lean tissue suggest that low EE in African American women is mediated by low volumes of metabolically active organ mass.