Study finds that people sit more hours a day than they sleep, raising the risk of chronic health conditions
THURSDAY, Nov. 29, 2012 (HealthDay News) -- For women who love that great, self-satisfied feeling after a workout, a new study could be a disappointing surprise. Regular exercise, the study found, does not reduce the risk of an otherwise sedentary lifestyle.
Women who exercise regularly actually spend as much time sitting down as those who don't get much exercise, and thus may be susceptible to a greater risk of diabetes, cardiovascular disease, obesity and premature death, the study revealed.
"We spend the vast majority of our time not exercising," said Lynette Craft, lead author of the study and an adjunct assistant professor of preventive medicine at the Northwestern University Feinberg School of Medicine, in Chicago. "It's important to think about how you spend your entire day and what you're doing in your non-exercise time."
Several previous studies have shown that men and women who sit for long periods of time -- even those who routinely exercise -- are more likely to develop chronic health conditions. The new study objectively measured sedentary or sitting time and compared it to the amount of sustained moderate or vigorous activity that people get, rather than relying only on self-reported surveys.
This study, published recently in the International Journal of Behavioral Nutrition and Physical Activity, set out to learn whether people who exceed the federal government's current Physical Activity Guidelines for Americans -- getting at least 150 minutes of moderate physical activity a week -- are less sedentary than are those who don't meet the guidelines.
Researchers wondered if there could be an unheralded but valuable benefit to what they call incidental low-intensity physical activity, which might add up incrementally during the day. Such small activity spurts might include walking a few blocks for a sandwich on a lunch break, taking the stairs instead of the elevator or pushing a child on a swing at the park.
For the study, 91 healthy women between 40 and 75 years old wore activity monitors designed to capture periods of sitting, standing and walking, and bouts of moderate and vigorous activity, over seven days. None of the women participating in the study had a personal history of heart disease, stroke, cancer or diabetes, or a physical condition that limited their physical-activity level. They wore the devices for at least 10 hours a day.
Although study participants spent an average of 146 minutes in moderate or vigorous activity a week, they still spent the majority of their waking hours (63 percent) sitting. Time involved in sustained exercise took up only a small fraction of time every day (about 2 percent).
"We now sit even longer than we sleep," Craft said. "Often you don't realize how much time you spending sitting every day."
Craft said she doesn't want to play down the value of exercise, but people need to do more all day long. "Even if you're exercising regularly, you still have an elevated risk compared to non-sitters," she explained.
Some experts think we've gradually engineered physical activity out of our daily lives.
"Humans are by nature sedentary. It's not that suddenly people have become lazy and stupid," said Dr. Toni Yancey, professor of health policy and management in the School of Public Health at the University of California, Los Angeles. "What's changed very much is our environment."
Yancey said society doesn't force people to move. "We commute for long periods, sitting," she said. "Even at the workplace, we use email instead of getting up to talk with a person. We don't shop; we order things over the Internet."
Craft recommends that people grab every opportunity to stand up, walk and move during the day. "Set a timer so once an hour you'll get up," she suggested. "Stand up when you're on the phone. Get up during commercial breaks when you're watching television. Stand while you're folding the laundry."
The study was limited to women only and was not designed to determine a cause-and-effect relationship between sitting time and time spent in sustained moderate to vigorous activity.
The U.S. National Heart, Lung, and Blood Institute has more about the value of physical activity (http://www.nhlbi.nih.gov/health/health-topics/topics/phys/ ).
SOURCES: Lynette Craft, Ph.D., adjunct assistant professor, preventive medicine, Northwestern University Feinberg School of Medicine, Chicago; Toni Yancey, M.D., M.P.H., professor, health policy and management, School of Public Health, University of California, Los Angeles; Oct. 4, 2012, International Journal of Behavioral Nutrition and Physical Activity