The study included middle-aged and older adults who had knee osteoarthritis or were at high risk of developing the condition. It focused specifically on low-intensity exercise, like strolling through a shopping mall or walking around the living room during television commercials.
“This study shows that even light movement is beneficial,” lead author Dorothy Dunlop told Reuters Health.
“We’re asking the couch potato to get off the couch for two hours a day,” said Dunlop, from the Northwestern University Feinberg School of Medicine in Chicago. “You can get up when the commercials come on. You can walk around your block.”
Although public health officials and doctors sing the praises of moderate-intensity and vigorous exercise, the benefits of low-intensity activity remain unclear, the authors write in the British medical journal BMJ.
The new study suggests that any movement has the potential to forestall illness and disability, they add. However, it does not prove that engaging in light activities was the reason certain people maintained their health.
Dunlop and her team studied 1,680 adults between 49 and 83 years old who were living independently in one of four U.S. cities and did not have a disability. All of them had knee osteoarthritis or risk factors for the condition, which occurs when the protective cartilage around the joint wears down over time.
At the beginning of the study, participants wore accelerometers on their hip to measure their physical activity levels during waking hours for seven consecutive days.
Two years later, 149 of those studied had become disabled and could no longer perform basic activities on their own.
The more time participants spent stationary, the more likely they were to develop problems getting around.
As expected, both moderate and vigorous exercise were linked to long-term benefits. But even after the researchers accounted for time spent on those higher-intensity activities, light movement was still associated with a lower risk of disability.
Four or more hours a day of light activity was tied to a 30 percent lower risk of disability, Dunlop said.
What’s more, when the researchers included people who already had disabilities at the start of the study, they found those who engaged in light activity were less likely to see their condition worsen.
“Even among people who cannot do very much moderate activity, there was a strong benefit to participating in light activity to reduce the risk of developing disability as well as disability progression,” Dunlop said.
“We hope this will provide an additional route to better health and will add to the advice physicians give their patients,” she said. “It may be a new route for interventions for people who have health limitations.”
U.S. federal guidelines issued in 2008 call for adults to get at least 150 minutes a week of moderate exercise. They stress the health benefits of all physical activity but say nothing specifically about light-intensity exercise.
Exercise scientist Todd Manini told Reuters Health he has no doubt about the benefits of moderate exercise. But Manini, from the University of Florida College of Medicine in Gainesville, said he remains unconvinced about the benefits of low-intensity movement.
Manini studies the health advantages of exercise and sits on a committee scheduled to make recommendations for new federal exercise guidelines in 2018. He was not involved in the new research.
One limitation of the study is that it cannot determine cause and effect, Manini said. He wondered, for example, if the people who performed more low-intensity activities might have been in better shape to begin with.
He also questioned the range that researchers used to measure low-intensity exercise and whether it could have been so broad that it encompassed moderate exercise as well.
Nevertheless, he praised the study for contributing to a growing body of literature about light-intensity exercise.
“I would love to tell people if you do your light activity, you’re going to get all the benefit,” Manini said. “But it could be a dangerous place to go.”
He fears that expanding federal exercise guidelines to recommend low-intensity activities might provide excuses for people who could exercise more vigorously but would instead move just a little and mostly remain chained to their couches.
But, he said, “You just can’t go wrong with the recommendation of, ‘Just keep moving.’”