Is It Possible to 'Overdose' on Exercise? Yes, Warns Expert

It is possible to "overdose" on exercise, an expert has warned to Newsweek, as the American Heart Association publishes new guidelines on how to work out safely.

Barry A. Franklin, a fellow with the American Heart Association and professor of internal medicine at Oakland University William Beaumont School of Medicine, told Newsweek "it appears possible to overdose on exercise," suggesting it's an example of having "too much of a 'good thing.'" He made the comments as the American Heart Association released a statement on the risks associated with exercising published in the journal Circulation, which featured a review of over 300 scientific studies.

Franklin and the other authors of the statement stressed that exercising is known to be good for the heart. For instance, exercising more has been linked to a 30 to 50 percent drop in deaths related to cardiovascular problems, the authors said.

However, in the 13 years since the association released its last statement on this topic, more have begun taking part in endurance training and long-distance events, like marathons and triathlons, and doing high-intensity interval training that features short bursts of intense activity. People have taken up intense regimes "with the belief that 'more is invariably better,'" Franklin said.

This isn't necessarily the case, especially when people who have heart disease or structural abnormalities take up tough regimens. Sometimes such people die, he said.

One study the team looked at on marathon runners in the U.S. between 2000 and 2010 found men were more at risk of having issues like heart attacks, and that the incidence rose over time. A separate paper on triathlons in the U.S. between 1985 to 2016 found of the 135 people who had sudden cardiac deaths, 26 were taking part for the first time. These findings indicate more people with underlying cardiovascular problems were taking part in these events, the authors wrote.

Franklin said recent studies suggest that extreme endurance regimes may, in some people, increase the levels of calcium in the heart—which is a sign of potential or early heart disease—or the chance of developing an irregular heart rhythm, which can trigger transient ischemic attacks and strokes.

However, "despite such caveats, the benefits associated with long-term exercise training outweigh the risks for the majority of the population," Franklin emphasized.

People should aim to take part in moderate to intense aerobic activity for a minimum of 30 minutes per day, five days a week, or vigorous to intense activity for a minimum of 20 minutes five days each week, or combinations thereof, Franklin and colleagues wrote.

The safest way for an inactive person to start an exercise regimen, according to Franklin, is to start walking on level ground at a moderate pace, at between 1.5 to 3 mph. Gradually increase the speed of walking, for instance to 4 mph, and continue if you have no chest pain or pressure, extreme shortness of breath or very rapid or irregular heart rhythms. Keep up with this for about six to eight weeks before moving on to higher intensity activities.

"Regardless of how active you were decades earlier, do not start with running, jogging, racquetball or graded treadmill walking. And stop exercising if you develop symptoms and seek medical review and clearance before resuming your exercise regimen," he said. Franklin stressed even highly fit endurance athletes are not immune to heart disease or structural abnormalities in the cardiovascular system "which, when combined with high-intensity exercise, especially when unaccustomed, could have lethal consequences."

The takehome message, Franklin said, is that "exercise is medicine," but that there are valid reasons both to take up and also avoid vigorous exercise "but not for mild to moderate exercise."

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A stock image shows a woman working out at the gym. Getty