Scientists identify one fitness habit that may matter most for longevity
Should you go all in on walking—or switch up your workouts during the week? A new study compares the longevity benefits of various types of popular exercises.
Is your workout routine feeling stale? Shaking up your exercise routine can help—and it might just increase your chance of living longer too.
While it’s well documented that exercise lowers your associated mortality risk, few studies so far have investigated whether or not diversifying your exercise matters. But according to a new Harvard University study, in the long term, exercise variety makes a significant difference in longevity, regardless of how long you sweat.
The study, published on January 20 in BMJ Medicine, focused on 111,000 nurses and health professionals who routinely completed surveys about their exercise habits over a span of 30 years. The participants logged their total time spent on multiple physical activities, including gardening, biking, running, strength training, tennis, climbing stairs, and yoga. The study authors then grouped participants by activity variety.
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The most diverse group—those who engaged in the highest number of distinct activities per week—had a 19 percent lower associated mortality risk than the least diverse group, results showed.
The takeaway? “It’s probably better to spread the limited energy on multiple physical activities instead of sticking to a single high-intensity one,” says Yang Hu, the study author and a research scientist at Harvard’s department of nutrition.
However, since the data is self-reported, participants may have exaggerated their weekly exercise. The study also observed a trend between exercise diversity and longevity, but cannot conclude that variety in movement directly causes lower mortality without a clinical trial. “The findings should be interpreted cautiously,” says Duck-chul Lee, director of the Physical Activity Research Center at the University of Pittsburgh.
Still, the study is well done and interesting, Lee adds. Instead of focusing solely on the advantages of combining aerobic exercise and weight-lifting, like prior sports research suggests, “this study includes various types of popular exercises.”
Is all exercise created equal?
While more research is needed, it’s not a far-fetched idea that diversity in exercise leads to healthier outcomes. One reason is because different activities expend distinct amounts of energy—for example, your body requires less energy leisurely walking compared to running.
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To compare activities, researchers assigned a metabolic equivalent task (MET) score to each survey category. Higher-intensity activities like jogging received a higher MET score than lower-intensity activities like gardening. This MET score was multiplied by the amount of time study participants engaged in this activity per week.
“Without using a common unit, it’s difficult to compare the intensity of jogging for half an hour with swimming for an hour, for instance,” Hu says.
Longevity outcomes also depend on exercise type and intensity, research shows. Some moderate exercises, like speed walking, have a linear relationship with reducing mortality risk; the more one speed walks, the more the risk goes down.
But more isn’t always better. According to a 2015 paper Lee authored, people who jog may lower their mortality risk only up to a certain point. In this study, joggers who ran even less than one hour saw significant decrease in mortality risk. But study participants who ran more frequently—more than two and a half hours a week—were not “associated with better survival compared to sedentary non-joggers.” In other words, benefits begin to plateau or even drop once someone works out too long or too hard. Lee found the same might be true when it comes to resistance training.
“Some studies suggest that more extreme levels of physical activity might even be associated with increased hazard ratio,” says Fabian Schwendinger, a researcher at the University of Basel’s Department of Sport, Exercise and Health.
The Harvard study also indicates a maximum exercise window: approximately three hours of vigorous activity or six hours of moderate-intensity activity per week.
“Doing higher activity level is perfectly fine, it is just that no additional health benefits would be gained further,” Hu says. “One who can run marathons everyday may not have a lower risk of dying than people who do regular brisk walking.”
The biological mechanisms behind this are unclear. Some experts theorize that overworking your body may increase chronic inflammation or arterial stiffness, both which have been shown to increase risk of cardiovascular disease.
“We need more data, especially from clinical trials, to examine associations of different types of exercise on various health outcomes,” Lee says.
Why exercise variety is key
Interestingly, Hu’s study found that regardless of how much a person worked out, variety improved participants’ longevity. When it came to reducing risk for cardiovascular disease, respiratory disease, or cancer, the most diverse exercise group had 13 to 41 percent lower risk compared to the least diverse group.
Although the study doesn’t investigate why exactly, it’s likely because multiple exercises offer complementary benefits.
“Engaging in a variety of physical activities may promote complementary physiological adaptations by exposing the body to different metabolic and neuromuscular demands,” Schwendinger says.
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Lee’s team conducted a 2024 study that found participants who only engaged in aerobic exercise saw increased peak oxygen consumption, thus improving their cardiorespiratory health. Nevertheless, their muscle health remained weak. Participants who did both aerobic exercise and resistance training, however, saw gains in both areas.
While the Harvard study did not test which group of activities maximized results in regard to longevity, Hu says that pairing strength training and an aerobic exercise—say yoga and tennis or weight-lifting and jogging—is a safe bet.
“The former enhances muscle strength and keeps lean body mass while the latter strengthens the circulation system, both of which are critical for longevity,” he notes.
The World Health Organization and U.S. Physical Activity Guidelines agree. “There is a growing body of literature supporting that engaging in both resistance and aerobic exercise might be linked to more optimal health benefits than either alone,” Schwendinger says.
