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Women walking for health and fitness. How much is enough?
J J Duncan1, N F Gordon, C B Scott
1Division of Exercise Physiology, Cooper Institute for Aerobics Research, Dallas, TX 75230.
Objective:
We studied whether the quantity and quality of walking necessary to decrease the risk of cardiovascular disease among women differed substantially from that required to improve cardiorespiratory fitness.
Design:
A randomized, controlled, dose-response clinical trial with a follow-up of 24 weeks.
Setting:
A private, nonprofit biomedical research facility.
Participants:
One hundred two sedentary premenopausal women, 20 to 40 years of age, were randomized to one of four treatment groups; 59 completed the study (16 aerobic walkers [8.0-km/h group], 12 brisk walkers [6.4-km/h group], 18 strollers [4.8-km/h group], and 13 sedentary controls). Eighty-one percent were white, 17% black, and 2% Hispanic.
Intervention:
Intervention groups walked 4.8 km per day, 5 days per week at 8.0 km/h, 6.4 km/h, or 4.8 km/h on a tartan-surfaced, 1.6-km track for 24 weeks.
Main Outcome Measures:
Fitness (determined by maximal oxygen uptake) and cardiovascular risk factors (determined by resting blood pressure and serum lipid and lipoprotein levels).
Results:
As compared with controls, maximal oxygen uptake increased significantly (P less than .0001) and in a dose-response manner (aerobic walkers greater than brisk walkers greater than strollers). In contrast, high-density lipoprotein cholesterol concentrations were not dose related and increased significantly (P less than .05) and to the same extent among women who experienced considerable improvements in their physical fitness (8.0-km/h group, +0.08 mmol/L) and those who had only minimal improvements in fitness (4.8-km/h group, +0.08 mmol/L). High-density lipoprotein cholesterol also increased among the 6.4-km/h group, but did not attain statistical significance (+0.06 mmol/L; P = .06). Dietary patterns revealed no significant differences among groups.
Conclusion:
Thus, we conclude that vigorous exercise is not necessary for women to obtain meaningful improvements in their lipoprotein profile. Walking at intensities that do not have a major impact on cardiorespiratory fitness may nonetheless produce equally favorable changes in the cardiovascular risk profile.