The links were especially strong for cardiovascular disease and neurological conditions. The data showed that people who lifted weights, no matter how infrequently, were less likely to die from heart attacks or Alzheimer’s disease compared with people who did no resistance training.
But the scientists also zeroed in on the “Goldilocks” level of weekly lifting – the number of minutes per week that isn’t too little or too much, but just right – associated with the greatest longevity benefit overall, whether people also exercised aerobically or not.
They seem to have found it.
Links between longevity and lifting haven’t been studied much
For decades, researchers have been studying the precise amounts of aerobic exercise we’re likely to need to live long, healthy lives. The scientific consensus, quantified in the current physical activity recommendations from the Department of Health and Human Services, is at least 150 minutes per week of moderate exercise, such as speedy walking.
Smaller amounts of aerobic activity, even a few minutes a day, likewise have been associated in recent studies with greater longevity and health, especially if the effort involved is challenging.
“But less is known about how resistance exercise relates to long-term mortality risks,” said Edward Giovannucci, a professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health and senior author of the new study, “especially at different amounts and combinations with aerobic activity”.
HHS recommendations suggest two days a week of some kind of muscle-strengthening exercise but provide no other details.
Studying the exercise habits of almost 150,000 people
So Giovannucci and his colleagues decided to mine the available data, hunting for the potentially most effective “dose” of strengthening exercise for longevity.
Conveniently, Harvard oversees a number of large studies and databases that have gathered health information from nurses and other healthcare workers for the past 30 years.
Participants in these studies have repeatedly filled out detailed questionnaires about their exercise habits over the years, including how many minutes each week they ran, walked, cycled, swam or otherwise worked out aerobically, as well as how often they lifted weights (focusing, in particular, on using weight machines and free weights).
The researchers pulled data for 147,374 of these men and women, most of them middle-aged when they joined the studies, and cross-checked them with death records for the following 30 years or so.
Then, using complex models of how different types and amounts of activity related to lifespans, they analysed the intersections of exercise and mortality.
Lifting weights 90 to 120 minutes a week has been linked to lower death risk. Photo / 123rf
Finding the sweet spot for lifting
The sweet spot for weekly resistance training – the amount associated with the maximum longevity benefit per minute – was easy to detect.
It came at anywhere between 90 and 119 minutes per week of lifting.
Lifting for that much time each week was linked to a 13% lower risk of dying prematurely from any cause and a 19% lower risk of dying from heart disease.
Somewhat surprisingly, the risks of dying from neurological diseases, such as dementia, were improved the most, declining by 27%.
Smaller amounts of resistance exercise, including even a few minutes a week, likewise were linked to longer lives, though the declines in mortality risk were slighter.
After 119 weekly minutes, any gains flattened; lifting more didn’t raise mortality risks but didn’t further improve them, either.
Doing both aerobic and resistance exercise was best
Perhaps most important, the gains in lifespan associated with lifting came on top of any that people might be getting from aerobic exercise, since the researchers controlled for that kind of exercise. In effect, the gains were additive, and doing both was best. “People who combined aerobic exercise with resistance training generally had the lowest mortality risk,” said Yiwen Zhang, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health who led the study.
“Given its large sample size and long-term follow-up period, with repeated measures of resistance-training behaviours, the findings are convincing,” said David Scott, an exercise scientist at Deakin University in Australia who studies exercise and health but wasn’t involved in this research.
The study doesn’t show, though, how best to use the 90 to 119 minutes of lifting each week. Would three 30-minute workouts or 15 minutes a day be better for longevity than one 90-minute session? Is it better to lift heavier weights than light ones? Could push-ups and other calisthenics be just as effective as machine-based moves? “Future research is certainly needed” to answer those questions, Giovannucci said.
Combining weights with cardio may deliver greater longevity benefits. Photo / 123rf
The study also doesn’t explain how weight training reduces the risk of dying prematurely. But other research suggests that being strong improves mobility and helps prevent falls with age. Muscle mass is beneficial, too, for lifelong metabolic health, and resistance exercise probably improves brain health by releasing substances into the bloodstream that travel to the brain and jump-start processes there that help keep it youthful.
But even with the study’s many outstanding questions, its findings keep its authors lifting.
“I’ve been doing so for the past 25 years,” Giovannucci said, “typically two to three times a week, about 45 minutes each time,” landing squarely in the study’s sweet spot.
Zhang is still working her way there, she said, lifting lightly about twice a week, for about an hour in total. But, given the results of her research, “I’m aiming to build up.”