Dear Doctor: I saw on the news that if you work out for 11 minutes a day, you are protected from the bad stuff that happens from sitting too much. Is that really true? I’m stuck at my desk all day, and that’s not changing anytime soon.
Dear Reader: We think you’re referring to a recent study, published in the British Journal of Sports Medicine, which looked at the health outcomes of people whose lifestyles ranged from extremely sedentary to moderately active. According to the findings, even a small amount of daily exercise helped to mitigate the negative health effects of prolonged inactivity.
The conclusions outlined in the study caused quite a splash and have since popped up on TV, newspapers and magazines. And small wonder: Several years ago, research linked prolonged sitting -- that’s eight hours or more per day -- to an increased risk of premature death. With so many jobs, like your own, now tethering workers to their desks, people have become eager for information on how to lessen the ill effects.
This new research, which reexamines data collected in nine previous studies, focused on about 44,000 people who each wore an activity tracker to accurately monitor their daily movement. The participants, who were middle-aged and older, remained seated an average of 10 hours each day. When they did exercise, it consisted of short sessions -- eight to 35 minutes -- often simply walking at a moderate pace.
When the researchers looked at mortality rates in the years after the participants enrolled in the studies, they found the expected link between the people who exercised the least and an increased risk of premature death. The surprise came when quantifying just how much exercise it took to reverse the trend toward an earlier death. The answer was the 11 minutes of daily exercise that grabbed your attention in the news story you saw. It’s important to note that those 11 minutes of exercise did not, as you said in your question, completely erase the ill effects of prolonged sitting. However, the findings of the study do suggest that even a small amount of exercise appears to confer health benefits.
An important conclusion in the study, which headline writers didn’t get quite so excited about, is that the magic number when it comes to exercise appears to be 35. That is, the greatest benefit comes when someone engages in moderate exercise for at least 35 minutes per day. That’s actually in line with the current guidelines put forth by the Department of Health and Human Services. Specifically, at least 150 minutes of moderate aerobic activity, or 75 minutes of vigorous aerobic activity, spread out over the course of a week. Interestingly, several studies have suggested that those 35 minutes of exercise don’t have to happen all at once. Rather, they can be split up into several sessions throughout the day and still yield a similar benefit. That’s encouraging news for people who think they don’t have time to exercise. Let’s all celebrate by getting up out of our chairs right now and taking a brisk 10-minute walk.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
