Exercise is medicine - but how much of a dose do we need?
Posted January 31
For 10 years, the American College of Sports Medicine has been trying to convince a sedentary public that exercise is medicine, as good for what ails us as over-the-counter or prescription pills.
What began as a national campaign morphed into a global initiative, with the goal of getting physicians to prescribe exercise to their patients and suggest that they get "physical activity counseling."
But although the association between exercise and health is widely accepted, there seems to be no consensus on how much physical activity we need for optimal health. The World Health Organization recommends 2½ hours a week. A study funded by the Bill and Melinda Gates Foundation last year recommended five times that amount. And now there's new research suggesting that people who exercise only on weekends can reap significant health benefits.
While the studies seem contradictory, they have one thing in common: They conclude the more exercise you do, the healthier you'll be — up to a point.
Finding that sweet spot for you and your family can greatly reduce the chance that you'll get one of five common diseases. But if you're currently unable to run six hours or swim eight hours a week, the new findings on "weekend warriors" will at least encourage you to do what you can for the time being. But be careful — occasional exercise comes with its own set of risks.
Attention, weekend warriors
The "weekend warrior" study published Jan. 9 in the journal JAMA Internal Medicine has gotten lots of buzz for its promise of longer life with sporadic effort. The authors said that weekend-only exercise and "insufficient activity" patterns can cut mortality by 30 percent.
"Many midlife people with active family lives and burgeoning careers find it difficult to make time for regular workouts. As a result, fitness advocates often encourage a small-steps approach to exercise," wrote Amby Burfoot, winner of the 1968 Boston Marathon, in The Washington Post.
"Don’t be discouraged if you don’t have the time to train for a half-marathon, they advise. Focus on what you can do, not what you can’t. Anything is better than nothing. The new research seems to confirm this," Burfoot wrote.
That could be heartening to the estimated third of Americans who get no exercise at all, or those who fall into an exercise drought and despair of losing fitness and momentum.
Researchers analyzed the weekly exercise reported by 63,000 British and Scottish adults and found both the ones who worked out once or twice a week for 2½ hours or more and the ones who exercised just an hour were both around 30 percent more likely to outlive the completely sedentary.
But one subset of people fared even better: Those who exercised three or more times a week.
"These individuals tended to go longer and slower than less-frequent exercisers but logged impressive weekly totals of about 450 minutes. They had a 35 percent lower all-cause mortality rate," Burfoot explained.
That's similar to what a public-health researcher in Australia recommended in a report published last year.
Dismissing the recommendations of the World Health Organization as insufficient, the study concluded that we need five times that amount to significantly cut our risk of five types of disease: breast and bowel cancer, diabetes, heart disease and stroke.
“Although the first minutes of activity do (the) most for health, our research results suggest activity needs to be several times higher than current World Health Organization recommendations to achieve larger reductions in risks of these diseases,” lead author Lennert Veerman, of the University of Queensland, said in a statement.
His advice translates into exercise sessions that would be staggering for most people: 15 to 20 hours of brisk walking per week, 6 to 8 hours of running, 7 hours of cycling and eight hours of swimming.
Working with researchers at the University of Washington and Dartmouth College, Veerman analyzed 174 studies published between 1980 and 2016 and compared activity levels with the incidence of disease. Using a measure called "Metabolic Equivalent of Task" — or MET — he assigned values to minutes of vigorous activity, light activity or doing nothing.
As The Huffington Post explained, "Most health gains occur at a total activity level of 3000-4000 MET minutes a week which equals 12.5 to 16.5 hours of brisk walking or 6 to 8 hours of running a week."
But in their study, published in the journal BMJ, the researchers advocated not just for repeated, sustained periods of vigorous exercise, but also picking up the pace of everyday activities and chores.
"Focusing on a particular domain such as leisure-time physical activity, which represents only a small fraction of total activity, as was done by most studies, restricts the scope of applicability of the findings in the real world by limiting the opportunity of increasing activity in different domains in daily life (such as being more physically active at work, engaging more in domestic activities such as housework and gardening, and/or engaging in active transportation such as walking and cycling)," the authors said. "Taking into account all domains of physical activity increases opportunities for promoting physical activity."
While it's a problem that relatively few Americans have, there is some evidence that you can exercise too much.
Take it slow
In his memoir "What I Talk About When I Talk About Running," the novelist Haruki Murakami wrote that when people criticize him, "I go running for a little longer than usual. By running longer it's like I can physically exhaust that portion of my discontent."
As Murakami knows, in addition to offering protection from disease, vigorous exercise has been shown to have psychological benefits, such as quelling anxiety and reducing depression. Physical activity also treats ADHD and seems to slow cognitive decline as people age.
But despite the many benefits, weekend warriors should remember that sporadic physical activity can come with a cost: increased soreness at the first of the week, plus the possibility of injury.
A 2014 study found increased risk of serious injury among weekend-only athletes, although the author was uncertain whether it was because the exercisers were more easily fatigued or stressed, or just that they weren't as experienced those who worked out more frequently.
Moreover, physical exertion stresses the heart, which can lead to catastrophe if people try to do too much too soon. Recently in Thailand, where government leaders have been ordered to exercise for 90 minutes every Wednesday, a Bangkok official collapsed and died during an afternoon football game. And every year in the U.S., a few runners with preexisting conditions die from the stress of road races. And extreme amounts of exercise can lead to a condition called "athlete's heart," in which the heart becomes dangerously enlarged.
It's clear, however, that exercise benefits both mind and body in increments as little as 10 minutes, building gradually to an hour or more every day. A widely accepted rule of thumb is to increase your physical activity no more than 10 percent every week.