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Physical Activity and Improvements in Cardiorespiratory Fitness

Some exercise is good, and more is better.

The dose-response effect of physical activity in improving cardiorespiratory fitness was characterized in 464 postmenopausal women who were overweight and sedentary (mean age, 57; mean BMI, 32). The women were randomized to physical activity levels corresponding to 50%, 100%, or 150% of those recommended by an NIH panel, or to no exercise. During a 6-month follow-up, participants in the three intervention groups exercised a mean of 72, 136, and 198 minutes/week, respectively. Maximal oxygen uptake in these groups increased significantly and in a dose-dependent fashion, by roughly 4%, 6%, and 8% over a baseline level of about 15 mL/kg/min. There was no increase in walking separate from the prescribed exercise sessions for any of the intervention or control groups, nor was there any improvement in cardiac risk factors, including weight, body fat, cholesterol profile, or blood pressure.

Comment: These data confirm what many experts have recommended to patients for some time, and an accompanying editorial endorses this advice: Some exercise is good, and more is better. However, both baseline and final levels of maximal oxygen uptake were discouragingly low, and intervention patients did not change their baseline level of walking separate from the exercise program, despite considerable education and encouragement. The search for effective ways to promote exercise continues.

— Thomas L. Schwenk, MD

Published in Journal Watch General Medicine May 15, 2007

Citation(s):

Church TS et al. Effects of different doses of physical activity on cardiorespiratory fitness among sedentary, overweight or obese postmenopausal women with elevated blood pressure: A randomized controlled trial. JAMA 2007 May 16; 297:2081-91.

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• Medline abstract (Free)

Lee I-M. Dose-response relation between physical activity and fitness: Even a little is good; more is better. JAMA 2007 May 16; 297:2137-9.

• Original article (Subscription may be required)
• Medline abstract (Free)