The last few years have brought not-so-good news about how sitting for long hours every day—such as people do for commutes, work, travel or leisure—increases a person’s risk for heart disease, diabetes and an early death.
Even worse news was that this held true even if a person exercised regularly. It seemed a daunting, insurmountable health obstacle to overcome, especially for those who intentionally exercised to improve their health to avoid those negative health outcomes of being sedentary for a prolonged period of time.
One person wasn’t going to take this news at face value, so he looked into the research himself. He knows what to look for, too. His name is Mark Peterson, Ph.D., M.S., and he is an assistant research professor at the University of Michigan School of Medicine. Not only is he an expert in exercise science, but he also holds a master’s degree in biostatistics, so he can crunch numbers with the best of them. Peterson also works out for about an hour to 90 minutes on most mornings, but then he spends the remainder of his day sitting at work. After work, he relaxes for a couple more hours each evening with his wife and children. He thought, “Could this really be true? Is it possible that sedentary time is trumping my exercise time?”
He was going to find out, and he did. “What I found is that even though the studies were extremely well conducted, they didn’t necessarily tell the whole story. In many cases, the data were gathered with questionnaires, and people were simply asked if they exercised on a certain day or not. There wasn’t an accurate way to account for the intensity or duration of that exercise. And it was usually a totally subjective measure,” Peterson explains.
In the previous research, a casual 10-minute walk counted the same as 45 minutes of intense interval training, and that, Peterson says, “resulted in exercise not being found to have any impact on the increased disease risks associated with being sedentary.”
Peterson wanted to see what happened when accounting for exercise intensity. He pulled data from the National Health and Nutrition Examination Survey (NHANES), an ongoing study that gives detailed physical activity data on people. “The NHANES data provides objective measures of activity with acclereometers. So, we knew how hard and how long the people were exercising. And we looked at different levels, over several years: light, moderate and vigorous activity, as well as different combinations.”
Peterson found that those who engaged in the highest amount of moderate and vigorous activity daily weren’t at any increased risk for heart disease or diabetes, no matter how much sedentary time they logged. “As long as they were exercising hard and regularly, it didn’t matter if they also had a lot of sedentary behavior,” says Peterson.
And just what does this mean? It appears that a minimum of 30 to 45 minutes a day of moderate-to-vigorous activity, at least five days a week, provides protective effects against being sedentary. Peterson adds, “Reducing sedentary time is still a very important public health message. We should all try to move more, and sit less. But is shouldn’t be oversold, and the benefits of moderate to vigorous daily exercise shouldn’t be undersold.”
And that's good news on the exercise vs. sitting topic.