Even physically active women sit too much, study finds

Emerging research shows that prolonged sitting has significant health consequences -- and the new Northwestern study suggests that being a dedicated exerciser doesn't prevent women from spending too much of their day sitting.

This research is the latest indication that public health recommendations should be established to encourage Americans to limit the amount of time they spend sitting every day, said Lynette L. Craft, first author of the study and an adjunct assistant professor in preventive medicine at Northwestern University Feinberg School of Medicine.

"We all know someone who gets a good workout in every day, but then spends a large portion of their day sitting in front of a computer with few breaks," Craft said. "If these people could replace some of the sitting with light activity -- just getting up, moving around, maybe standing up when talking on the phone, walking down the hall instead of sending an email -- we do think they could gain health benefits."

The Northwestern research was done in collaboration with Ted Zderic, of the Pennington Biomedical Research Center and was published in the International Journal of Behavioral Nutrition and Physical Activity.

Past studies have shown that people who sit for extended periods of time -- even those meeting exercise recommendations -- are more likely to develop chronic conditions such as diabetes, obesity, cardiovascular disease and some cancers.

This was the first study to use an objective measuring device to examine the relationship between the type of exercise recommended in the government's Physical Activity Guidelines for Americans and sitting. The guidelines recommend adults engage in a minimum of 150 minutes of moderate intensity aerobic activity every week. Previous studies on physical activity and sitting have primarily relied on self-reported data.

While many of the women in the study met or exceeded 150 minutes of physical activity per week, in reality only a fraction of the women's days were spent being physically active. The women in the study spent an average of nine hours a day sitting. That number is consistent with previous results from much larger studies that examined the number of hours Americans spend sitting every day.

"I think some people assume, 'If I'm getting my 30 to 40 minutes of physical activity a day, I'm doing what I need to do for my health,'" Craft said. "Of course, exercise is very important and is associated with many positive health benefits, but negative health consequences are associated with prolonged sitting, and this study shows that just because you're physically active doesn't mean you're sitting less."

For the study, 91 healthy women ranging in age from age 40 to 75 wore an activPAL activity monitor device during waking hours for one week. The device, which was worn on the thigh, recorded time spent sitting, standing and stepping, and engaging in sustained 10-minute bouts of moderate-to-vigorous physical activity.

Trying to replace some sitting time with more light activity throughout the day -- along with the recommended bouts of moderate and vigorous exercise -- is an approach more Americans should try to take, Craft said.

Future studies are needed to further examine the relationship between the type of exercise recommended in the Physical Activity Guidelines for Americans and sitting. For example, various subgroups such as men, children and the elderly should also be studied, Craft said.

The Lynn Sage Breast Cancer Foundation, the Avon Foundation and the Edward G. Schlieder Educational Foundation supported the study.