Each week, Nuance goes beyond the basics, offering detailed, researched information on the latest science and expert insights on a much-talked-about health topic.
According to exercise, running is your workout, what humans have been doing since the caveman days of our species. There is no shortage of evidence that running is a source of health and longevity.
It’s one of the most popular forms of aerobic exercise, and a mountain of research has linked aerobic training with health benefits ranging from reduced cancer risk to improved cognitive performance.
A 2015 study found that even a modest amount of running (five to 10 minutes a day at a slow pace) was associated with a 28% reduction in all-cause mortality and an even greater reduction in the risk of death from heart disease.
“Runners, on average, lived three years longer compared to non-runners,” says study author Duck-Chul Lee, an associate professor of kinesiology at Iowa State University.
Long-term runners, those who keep for six years or more, seem to experience the greatest longevity benefits, says Lee.
Stronger and faster is not always the same as healthier.
But as running became more popular, so did longer distances. More people than ever are running marathons (and even ultramarathons), leading experts to question whether more is really better.
“Stronger and faster doesn’t always equal healthier,” says James O’Keefe, MD, a cardiologist and clinical associate professor at the University of Missouri-Kansas City School of Medicine.
Designing a car to win the Indy 500 is a very different goal than designing a car to run smoothly for 500,000 miles, says O’Keefe. Similarly, building a race plan to maximize speed and endurance is not the same goal as building a race plan to maximize longevity.
“Excessive strenuous exercise can actually erase some of the longevity benefits seen with moderate exercise,” he adds.
O’Keefe was once an avid runner. But he switched to other activities (including walking) after his research linked a lot of running to poor health. One of O’Keefe’s studies found that while modest amounts of running are a bulwark against disease and death, too much running actually erases those benefits.
“Stupid” runners, defined as people who ran more than 11 kilometers per hour and more than four hours a week, had mortality rates similar to those of sedentary adults, their study concluded.
Some researchers have disputed these findings. In response to the study, Martin Burtscher, MD, a professor at the Austrian Institute of Sport Sciences at the University of Innsbruck, noted that the study relied on self-reported pacing, which could bias the findings.
Burtscher says he hasn’t seen convincing evidence that people can “overdo” running, citing another recent study that found no decreased mortality benefits among people who did a lot of vigorous exercises.
But the study Burtscher mentioned looked at links between “physical activity” and mortality, not running. When you dig into recent research on running specifically, a good deal has found that running can increase a person’s risk of some health problems, especially those related to the heart.
The association between long-duration, intense endurance exercise and atrial fibrillation, a heart irregularity that can increase the risk of heart failure and stroke, is “well accepted in the scientific community,” says Eduard Guasch, MD, a researcher at heart health. at the Hospital Clinic of the University of Barcelona.
While running is incredibly good for you, even in small doses, there can be some risks associated with intense resistance training.
Guasch says it’s not yet clear how exercise can cause or contribute to the heart problem. One popular theory is that large amounts of resistance exercise “reshape” the heart in ways that cause dysfunction. But Guasch says that is still being debated. “There is no clear threshold beyond which we can confidently say that a specific athlete is at increased risk for [atrial fibrillation],” he says.
There is also some evidence that a person’s genetic predisposition to atrial fibrillation or other heart problems can make heavy running especially risky. And for people with underlying heart problems, running a marathon is associated with a small but measurable risk of sudden cardiac death.
The bottom line (at least for now) is that while running is good for you, even in small doses, there may be some risks associated with intense training. How much is too much? This question is hotly debated and depends on a person’s age, DNA, health status, and several other factors. “I think the current research available shows that there are a variety of durations and frequencies that provide longevity benefits for the average individual,” says Angelique Brellenthin, a postdoctoral researcher at Iowa State who, along with Lee, studied the effects of working on life.
Brellenthin’s research suggests an operating limit of 4.5 hours per week (up to six days per week). This fits in with other recent research that has found that 40 to 60 minutes a day of vigorous exercise is probably a safe upper limit for people looking to maximize their health.
O’Keefe offers more concrete numbers: “No more than 4.5 hours a week or 30 miles a week.”
There is no doubt that some experts disagree. And if you’re one of the many people who run marathons out of personal challenge, a sense of community, or sheer love of the sport, you may be heartened by the inconclusive state of the evidence. But if you’re hitting the pavement primarily to improve your health, recent research suggests less can be more.
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