We’ve long known — with excellent evidence — that regular physical activity is associated with numerous health benefits, including longer life.
What’s been less clear is whether vigorous exercise confers more benefits than moderate-intensity activity. Current guidelines in many countries, including the United States, Great Britain and Australia, suggest that the two are equal — as long as you do twice as much of the moderate-intensity activity. (The U.S. guidelines suggest a weekly minimum of either 150 minutes of moderate activity or 75 minute of vigorous activity.)
Well, those guidelines may be wrong — at least, according to a large study published online Monday in JAMA Internal Medicine. This study found that middle-aged people who engage in at least some vigorous activity live longer, on average, than those who engage only in moderate-intensity exercise — no matter how much time is spent doing the activity.
“Our findings suggest that vigorous activities should be endorsed in clinical and public health activity guidelines to maximize the population benefits of physical activities,” the authors conclude.
For the study, researchers from James Cook University in Australia collected data from 204,542 adults aged 45 to 75 who were enrolled in an ongoing Australian study on aging. The participants were asked questions about their exercise habits, and then followed for about 6½ years. During that time, 7,435 of them died.
An analysis of the data revealed that the risk of death was significantly lower, on average, among people who engaged in vigorous activity (such as running, cycling, aerobics or competitive tennis) than among those who did only moderate activity (such as gentle swimming, social tennis or vigorous gardening).
Furthermore, the more time they devoted to vigorous activity while exercising, the lower the risk.
Specifically, 8.3 percent of the people in the study who did not engage in either moderate or vigorous physical activity died during the follow-up period. That compared with 3.8 percent of those who did only moderate-intensity activity.
But the risk of death was even lower when vigorous activity was involved. Some 2.4 percent of the people in the study who undertook some high-intensity activity (less than 30 percent of all their exercise time) died during the follow-up period. And among those who did a significant amount of high-intensity activity (more than 30 percent of their exercise time), only 2.1 percent died.
In relative-risk terms, people in the less-than-30-percent group had a 9 percent lower risk of dying during the follow-up period than people who exercised at a moderate intensity. And those in the more-than-30-percent group had a 13 percent lower risk.
The results held even after adjusting for a variety of potentially confounding factors, including age, body mass index (BMI), existing chronic illnesses (diabetes and heart disease), fruit and vegetable consumption, marital status, educational level, smoking status and physical limitations.
“These findings suggest that even small amounts of vigorous activity may supplement the benefits of moderate activity alone,” say the authors.
The study’s results should not be interpreted as meaning moderate-intensity exercise isn’t beneficial. All exercise levels in the study were associated with a lower rate of death during the follow-up period when compared with no exercise.
Furthermore, the study has several important limitations. The participants self-reported their levels of exercise — and only once, at the start of the study. They may not have been completely truthful with their descriptions of their physical activity when they filled out the questionnaires, or they may have changed that activity during the course of the study.
Also, this was an observational study, which can find only a correlation between two things (in this case, exercise intensity and the risk of death), not a direct cause-and-effect connection. Factors not measured in the study (such as how long the participants had been exercising during their lives) may have influenced the results.
Still, the study’s findings suggest that “even small amounts of vigorous activity could help reduce your risk of early death,” said Klaus Gebel, one of the study’s co-authors, in a released statement.
“For those with medical conditions, for older people in general, and for those who have never done any vigorous activity or exercise before, it’s always important to talk to a doctor first,” he added. “[But] previous studies indicate that interval training, with short bursts of vigorous effort, is often manageable for older people, including those who are overweight or obese.”
You’ll find an abstract of the study on the JAMA Internal Medicine website. The full study is behind a paywall.