This pilot study paves the way for a larger, NIH-funded Study of Targeted Risk Reduction Interventions With Defined Exercise (STRRIDE), which will help define just how much physical activity -- in terms of intensity and frequency -- is necessary to improve a mildly overweight person's heart disease risk factors, says Krauss.
The larger study will measure effects of various exercise programs, including a two- or three-day-a-week regimen. Krauss tells WebMD, "There's a lot of confusion in the lay press about how much exercise we should be doing. As a community of health professionals, we say that doing something is better than nothing, that you can divide exercise into three parts, at 10 minutes each, and do it on your breaks or at lunch time. But we don't know whether that translates into health benefits; we really don't. It's not been proven."
Krauss compares his work with the famous Nurses Health Study, which showed that women who walked for exercise reduced incidence of cardiovascular events like heart attacks. The study also showed that more vigorous exercise gave the volunteers more small, incremental health benefits. However, the study was inconclusive, says Krauss. "It didn't show whether vigorous exercise was better for optimal benefit. In our study, we'll be measuring that."
Calling the study's results very promising, Virendra Mathur, MD, a cardiologist with the Texas Heart Institute at St. Luke's Episcopal Hospital in Houston, tells WebMD, "We've known for a very long time that moderate aerobic exercise is very helpful in not only preventing cardiovascular risk factors but also in reducing weight, improving control of hypertension and type 2 diabetes, reducing osteoporosis and fractures. I'm very happy to read that sometimes you can have the benefit of these exercise programs even without weight loss."
The study is preliminary and has limitations, says Mathur. "How long will health benefits last after people quit exercise programs? Will there be additional decreases in 'bad' cholesterol levels if they keep with the exercise program? Also, we don't know much about their diet -- did they start eating a lower-fat diet? Did they start making other smaller changes in their lifestyles? Were they walking faster in the parking lot, for instance? There are a lot of intangibles that aren't addressed here."