The study builds on earlier research, including from Stamatakis’ lab, exploring how to intensify the health benefits of even a little physical activity. But it also raises questions about whether it’s possible to overthink the simple walk.
Most of us aren’t moving enough
“This study is about identifying ways to maximise what people get out of their walking,” Stamatakis said.
Walking may be the most common physical activity for almost everyone. But many of us do little of it. Current physical activity guidelines recommend 150 minutes a week of moderate activity, which would include brisk walking.
But “75 to 80% of people are insufficiently active,” Stamatakis said, meaning they don’t meet those guidelines. Quite a few rarely exercise at all.
It should be possible, though, to make even the briefest amounts of movement better for us, Stamatakis and his colleagues have speculated. In past studies, they have shown that picking up the pace of brief daily activities, such as housework, is associated with lower risks for heart disease and early death. The extra intensity seemed to make everyday chores and actions more potent for people’s health.
But not everyone can or wishes to up the vigour of their vacuuming. Were there other ways to get more health bang from just being in motion, Stamatakis and his colleagues wondered? What about if people’s activities simply lasted a little longer?
15-minute walks are best
To find out, the scientists drew records for 33,560 men and women, most of them in their 60s, from the UK Biobank, a massive data bank of British health records. All Biobank participants provide extensive medical information when they join, and many wear an activity tracker for a week.
The scientists looked for participants who said they don’t formally exercise and whose activity trackers showed they typically accumulated fewer than 8000 steps a day, most of them far fewer. They also had to be free of diagnosed heart disease.
Using activity tracker data, the scientists divided people into groups, based on whether their longest daily walk lasted five or fewer minutes, 10 minutes or 15 minutes or more. They also checked death and hospital records for up to about a decade after people wore the trackers. Then the researchers cross-referenced to see who seemed to have had the longest and healthiest lives.
The results were consistent and clear. The men and women who’d walked for 15 continuous minutes or more had the lowest risks of heart attacks and other cardiovascular problems and were more likely than the other groups to still be alive. Similarly, those walking for 10 uninterrupted minutes tended to live longer and with less heart disease than those whose longest walk lasted only five minutes.
These effects held true even if people were taking about the same number of total steps each day.
Why? It’s likely that the longer walking bouts “meaningfully activated” and altered people’s cardiovascular and metabolic systems in ways the briefer walks couldn’t, the researchers speculate in the study.
“This is a very insightful and important epidemiological paper that sheds further light into the importance of being physically active,” said Darren Warburton, an exercise scientist at the University of British Columbia, who has studied the health effects of physical activity. He wasn’t involved in the new study.
Any activity is better than none
But the study shows association, not cause and effect, so it can’t prove longer walks necessarily lead to better health outcomes. People who walk longer might also be more interested in healthy eating and other good habits that influence their longevity as much as – or more than – their stepping behaviour.
The effects were most pronounced, too, in people walking the least. The people who took fewer than 5000 steps most days but grouped some of those steps into longer 10- or 15-minute walks showed relatively larger reductions in their risks for heart disease and early death than people taking closer to 8000 steps a day who likewise strolled for a quarter hour. In other words, if people rarely walked but sometimes walked longer, they got more out of those longer walks than people who generally walked more.
So, the true lesson of the study could be, just walk more. But if you can’t or really want to amplify the potential benefits of your daily steps, walk a bit longer sometimes.
That’s a message the study’s authors embrace. “We have a lot of data from other studies showing that any amount of physical activity is good,” said I-Min Lee, a professor of epidemiology at the Harvard T.H. Chan School of Public Health and a study co-author. So, sure, “if you have a choice and are able to, try to walk for more than 10 minutes at a time,” she said. “But the total amount of activity is what matters more than the pattern in which it’s accumulated.”