Is Too Much Exercise Dangerous?

Study shows that extreme exercise does not increase risk of death from heart disease

Laura F. DeFina, MD, FACP, President and Chief Executive Officer, Chief Science Officer The Cooper Institute®

“The known benefits of regular physical activity in the general population include decreased mortality, heart disease, diabetes, and many other medical conditions, which reminds us how important it is to participate in regular physical activity.”

Ben Levine, MD, Professor of Institute for Exercise and Environmental Medicine (IEEM) UT Southwestern Texas Health Presbyterian Hospital Dallas

Athletes come in all forms, from the professional athlete to the everyday runner. We know regular exercise is good for us, but there has been a lingering question about how much is too much. When it comes to the heart, can too much exercise actually be dangerous?

Researchers from The Cooper Institute and UT Southwestern Medical Center collaborated on a study of highly active individuals, now published in JAMA Cardiology. To find out if too much exercise increases the risk of heart disease and death with early hardening of the arteries.

“The current study shows no increased risk of mortality in high-volume, high-intensity athletes who have coronary artery calcium,” said Dr. Laura DeFina, President and CEO and Chief Science Officer for The Cooper Institute and first author of the study. “Certainly, these highly active people should review their cardiovascular disease risk with their primary care doctor or cardiologist, but there is no reason to think they can’t continue exercising at high levels.”

Coronary artery calcification (CAC) is a footprint of atherosclerosis, a disease in which plaque builds up in the arteries and gives rise to heart attack and stroke. While the majority of the highly active people in the study had low levels of coronary calcium, their risk of having CAC was 11 percent greater than those who exercised less. However, researchers determined that higher calcium levels did not raise their risk for cardiovascular or all-cause mortality.

“The question has never been whether exercise is good for you, but whether extreme exercise is bad for you. For the past decade or so, there’s been increasing concern that high-volume, high-intensity exercise could injure the heart. We found that high volumes of exercise are safe, even when coronary calcium levels are high,” said Dr. Benjamin Levine from UT Southwestern Medical Center. Dr. Levine is a Professor of Internal Medicine and Director of the Institute for Exercise and Environmental Medicine, a collaboration between UT Southwestern and Texas Health Presbyterian Hospital Dallas.

Researchers from The Cooper Institute and UT Southwestern studied data from the Cooper Center Longitudinal Study. Over 21,000 generally healthy men, ages 40 to 80 and without cardiovascular disease, were followed for mortality between 1998 and 2013.

The participants, a majority of them in middle age, reported their physical activity levels and underwent coronary calcium scanning. Most were predominantly runners, but some were cyclists, swimmers, or rowers. Some even trained in three of these sports. An exercise routine of this level may look sometime like this:

• Running 6 miles/hour for 1 hour, 5 days/ week

• Walking 3.5 miles/hour for 2 hours, 7 days/week

• Biking 10-12 miles/hour for 1 hour, 7 days/week

• Swimming 1 hour 15 min, 7 days /week

“The known benefits of regular physical activity in the general population include decreased mortality, heart disease, diabetes, and many other medical conditions which reminds us how important it is to participate in regular physical activity as recommended by the 2018 Physical Activity Guidelines,” said Dr. Laura DeFina.

The updated Physical Activity Guidelines for Americans recommends 150-300 minutes per week of moderate-intensity aerobic physical activity or 75-150 minutes per week of vigorous intensity.

“The takeaway from this study is that it is safe to exercise at high levels, even if you have clinically significant coronary calcium,” said Dr. DeFina. “Exercise is still the best preventive medicine.”

“Exercise is still the best preventive medicine.” - Dr. Laura DeFina