Endurance Training, Your Heart May Be At Risk

The summer months are upon us, and therefore, it’s time to train for those long-distance marathons, bicycle races, biathlons, and triathlons.

But before you lose track of just how hard you’re training, you might want to consider looking into new information provided in the June issue of Mayo Clinic Proceedings , which suggests excessive endurance training can have negative long-term health effects.

What’s the risk?

The study does not contradict the fact that regular exercise is still highly effective for the prevention and treatment of many common chronic illnesses—and beneficial for overall cardiovascular and long-term health.

Where exercise becomes a risk is during long-term training for extreme endurance exercise, which can create temporary structural changes within the cardiovascular system and elevate markers for injury. These signs of risk typically disappear within one week after intense training, but over months and years of repetitive injury, athletes may develop conditions such as patchy scarring of muscle tissue in the heart and an increased susceptibility to irregular heart rhythms.

The study cites a case where 12 percent of seemingly healthy marathon runners showed signs of patchy myocardial scarring. The rate of coronary heart disease was also higher among marathon runners in the study’s two-year follow up.

Coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening may also be conditions associated with chronic excessive exercise.

"Physical exercise, though not a drug, possesses many traits of a powerful pharmacologic agent,” says lead author James H. O'Keefe, MD, of Saint Luke's Hospital of Kansas City, MO. "However, as with any pharmacologic agent, a safe upper dose limit potentially exists, beyond which the adverse effects of physical exercise, such as musculoskeletal trauma and cardiovascular stress, may outweigh its benefits."

Set limits for yourself

Researchers identified that lifelong exercisers generally are in better health than people who don’t exercise regularly. Regular exercisers generally have low mortality and disability rates and excellent functional capacity. Further investigation is needed to identify who might be at risk for effects of adverse heart conditions related to excessive exercise.

There is no claim that exercise is bad for you, but make sure to know your limits. Markers for health conditions within the study typically disappeared within just one week of rest after intensive training.

While not everyone will be training for an ultra-marathon this summer, it’s important to reduce the risk of injury when exercising.