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Article Excerpt
Abstract: Despite the known benefits of exercise, 60% of African American women are sedentary. The efficacy and dose-response effects of low intensity exercise performed in community settings by overweight sedentary women have not been established. The purpose of this study was to examine the effects of two intensities of walking on level of exercise maintenance and on cardiovascular risk factors in sedentary, obese African American women. A two group, randomized experimental approach was used to test 45-70 year old postmenopausal obese African American women, measuring age, self reported ethnic affiliation, height, weight, socioeconomic status, diet history, menopausal status, exercise volume, dietary restrictions, medication use, and medical conditions precluding participation. Group one walked three days/week; group 2 walked 5 days/week; both groups walked at 65 % of their target heart rate reserve.
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Analysis indicated that there were no differences in the group characteristics in body composition, blood lipids, and fasting blood sugars at base line. A mixed-effects repeated measures analysis of variance found differences for BIA and hip size over occasions (baseline, 12, and 36 weeks) but neither between treatments (3 per week versus 5 per week) nor their interaction. Repeated measures ANOVA showed significant differences among the walk groups in body fat measures by bioelectric impedance and waist-to-thigh ratio.
Minority women are at particular risk for obesity, and despite the known benefits of exercise on obesity, 40% of African American women report no leisure time exercise (Crespo, Smit, Andersen, Carter-Pokras, & Ainsworth, 2000). Thirty-five percent of African American women in the child bearing years and fifty percent ages 45-55 are overweight (Crespo et al. 2000). The effectiveness of exercise in reducing CHD risk factors in women is seen in improved lipid profiles, lower blood pressures, reduced body fat, and increased metabolic rate. Examinations of the dose-response effect of exercise have demonstrated that the most significant reductions in rates of CHD are found in individuals engaging in moderate exercise, with the greatest benefits occurring when sedentary individuals begin a program of regular exercise (Haskell, 1994). The efficacy and dose-response effects of low intensity exercise performed in community settings by overweight sedentary women have not been established.
The beneficial effects of exercise have been studied principally during and following strenuous exercise. The problem is to find an exercise protocol that is low enough intensity to ensure exercise maintenance, yet is of sufficient intensity to produce beneficial effects on CHD risk factors. Nurses in community-based treatment programs recognize the importance of physical activity but currently have no data except for laboratory trials and treadmill data to guide recommendations for exercise. The purpose of this study was to examine the effects of two frequencies of walking on level of exercise maintenance and on cardiovascular risk factors in sedentary, obese African American women. The specific aims were to: 1) Compare the effects of two frequencies of moderate intensity of exercise in African American women on blood lipids, body fatness and fat distribution, and exercise tolerance, and 2) Determine the effects of two frequencies of exercise on exercise maintenance in sedentary, obese minority women.
BACKGROUND AND SIGNIFICANCE
Exercise has been shown to have beneficial effects on cardiovascular risk factors such as overweight and obesity, and mortality, particularly in women. (Sopko, Obarzanek & Stone, 1992). Non exercisers, compared to exercisers, have twice the risk for weight gain (Ross, & Rissanen, 1994). Other benefits of exercise in CHD risk reduction include reduced LDL-C, serum cholesterol and triglycerides, reduced blood pressure, and increased metabolic rate (Haskell et al. 1992).
There has been some interest recently in the dose-response issue, involving both intensity and frequency. Ready and colleagues examined two frequencies of walking on cardiorespiratory fitness, body composition and lipids in non-obese postmenopausal women at 60% of peak VO2 max (Ready et al. 1996). A decrease in body fat was demonstrated in both groups, but without changes in blood lipids. In a randomized clinical trial (Duncan, Gordon, & Scott, 1991), strollers, moderate and aerobic walkers were compared on cardiovascular risk outcomes. Aerobic capacity improved among women in all groups, with those women engaging in the most vigorous activity improving the most. Surprisingly, changes in HDL-C were not related to the intensity of the intervention.
In 1994, a group of experts from the American College of Sports Medicine and the Centers for Disease Control and Prevention presented a consensus statement regarding the recommendation that all U. S. adults should accumulate 30 minutes or more of moderate intensity activity on most days of the week. The shift in emphasis from physical "fitness" to "health benefits" resulting from physical activity reflects the fact that most individuals are unlikely to engage in physical activity at intensities previously recommended and further, the risk of musculoskeletal injury increases with higher intensities (Haskell, 1994). The greatest benefits in all end points occur when sedentary individuals begin aerobic, moderate intensity activity (Paffenbarger, Hyde, Wing & Hsieh, 1986; Gettman, Pollock, Durstine, Ward, Ayres & Linnerud, 1996; Duncan et al., 1991). In October of 2000, Health Canada and the United States Centers for Disease Control and Prevention...
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