Effects of Resistance Training and Ambulation on Cardiovascular Risk Factors in African-American Women

The purpose of this study was to evaluate the effects of an increase in daily walking alone and the effects of increased daily walking combined with a progressive resistance training (RT) program on cardiovascular disease (CVD) risk factors in previously low-active, obese (mean BMI: 35 +/- 6 kg/m2), middle-aged (mean age: 49 +/- 5 years) African-American (AA) women. Height, weight, waist and hip circumferences, body composition variables via dual-energy X-ray absorptiometry, resting blood pressure, fasting glucose, high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), glycosylated hemoglobin (HbA1c), C-reactive protein (CRP), and fibrinogen were measured in 32 AA females before and after a 12-week exercise intervention. Subjects were randomly placed into one of two exercise training groups. One group was instructed to increase their daily walking to greater than or equal to 10,000 steps/day (W; n=17) and the other group was given the same walking prescription, but additionally resistance trained 2 days/week (WRT; n=15). Subjects performed 3 sets of approximately 12 repetitions of 10 exercises for all of the major muscle groups. Strength was evaluated for the upper and lower body by performing 1-repetition maximum tests using the chest press and leg extension exercises, respectively. A two-way repeated measures ANOVA was performed to examine changes between the two groups. Significance was accepted at p<0.05. Both W and WRT significantly increased daily walking (W: 5,480 +/- 2,162 to 7,528 +/- 2,046 steps/day; WRT: 4,833 +/- 1,820 to 7,412 +/- 1,728 steps/day; p<0.01), however neither reached their goal of greater than or equal to 10,000 steps/day. WRT significantly increased upper (101 +/- 13 to 118 +/- 15 kg) and lower body (105 +/- 20 to 123 +/- 23 kg) strength (p<0.01) and W showed no change for either measure. Significant interactions occurred for waist circumference, gynoid fat mass, and total fat mass. The WRT group had significant reductions in waist circumference (92.4 +/- 12.2 to 90.6 +/- 11.5 cm; p<0.01), fat mass (40.9 +/- 11.2 to 39.9 +/- 10.7 kg; p=0.01), and gynoid fat mass (8.0 +/- 2.1 to 7.9 +/- 2.0 kg; p=0.01) while the W group had no changes. Values for body weight, BMI, and lean body mass did not significantly change in either group after the 12-week intervention compared to baseline. There were some time effects for percentage of body fat (44.8 +/- 6.2 to 44.1 +/- 6.0%; p=0.02), HbA1c (6.0 +/- 1.3 to 5.7 +/- 1.1% kg; p=0.03), and mean blood glucose calculated from HbA1c (124 +/- 42 to 114 +/- 34 mg/dL; p=0.03). These variables significantly improved in the WRT and showed no change in the W group. Unfavorable changes were shown for fibrinogen in the WRT group (472 +/- 128 to 525 +/- 144 mg/dL; p=0.05) and for fasting glucose in the W group (123 +/- 33 to 132 +/- 42 mg/dL; p=0.04). Neither intervention had an effect on systolic or diastolic blood pressure, HDL-C, TG, total cholesterol, or CRP. Although both interventions elicited a significant improvement in walking volume, results showed that this sample of obese, middle-aged AA women was not compliant to a pedometer-based walking program as indicated by the failure of either group to obtain the prescribed 10,000 step/day goal. These findings showed that RT combined with an increase in walking volume had more favorable results on body composition variables compared to an increase in walking alone. The reduction in waist circumference may have significant health implications for other risk factors of CVD, particularly if an increase in ambulation is continued for a time period longer than 12 weeks. It was also concluded that RT combined with a pedometer-based walking program may be more effective than walking alone on long-term blood glucose control.