“A lot of information on physical activity provided to women is very general, encouraging daily activity, but not specifically what kind,” says Keri Gans, a spokesperson for the American Dietetic Association. “This study encourages an activity that is not expensive and that almost all women can easily engage in. And if a woman is presently a walker, it’s good to know that she must pick up her pace.”

Biking and walking are easier than many other forms of exercise to incorporate into everyday life, Lusk points out. “[They] can be a routine part of the day, so you can get your physical activity as a normal part of the day,” she says.

The study participants were all nurses and are part of a larger, national study on health and lifestyle that began in 1989. Women with physical problems that make regular exercise difficult were excluded from the current study, as were women who reported chronic health conditions such as heart disease, diabetes, or cancer.

At the start of the study, half of the participants reported walking slowly, 39% said they walked briskly, and 48% said they biked (including working out on a stationary bike).

By 2005, the average physical activity had increased slightly but remained very low overall. Participants walked briskly for just one hour per week, on average, and biked for only about 18 minutes per week. Meanwhile they sat around the house for about 2.5 hours a day.

Current guidelines recommend that adults get at least 30 minutes of moderate-intensity exercise on most days of the week, a goal that many women in the study appear to be well below.

Individuals can’t bear all of the blame for that inactivity, Lusk and her colleagues suggest. Their physical surroundings may also be partly responsible.

Although some cities and towns have encouraged walking and biking (by adding sidewalks and bike lanes, for instance), the U.S. remains a “car-centric nation,” they write.

Nine percent of commuters in the U.S. walk to work and just 0.5% bike, according to data cited in the study. By contrast, in the Netherlands, where the roads are more bike-friendly, 22% of commuters walk to work and 27% bike.

“We need to provide the infrastructure or facilities so that more people could comfortably bicycle,” Lusk says. “In the U.S., the emphasis has been on the walking environment and not on the bicycling environment.”