Skip to content

Strenuous Exercise: Could It Bad for the Heart?

Key findings

  • The number of endurance exercisers continues to grow, giving clinicians a unique population to manage
  • Long-term strenuous exercise is linked to atrial fibrillation, but the mechanism eludes researchers
  • A registry could be established to characterize behaviors of strenuous exercisers

Research has confirmed that moderate-intensity exercise on a regular basis is cardioprotective. However, recent studies, with limited data and mechanistic uncertainties, have suggested that regular high-intensity exercise can lead to adverse cardiovascular outcomes.

Epidemiological data have suggested that strenuous physical activity on a long-term basis is associated with relative decreases in mortality benefit, while long-term training for endurance athletes has been associated with early-onset atrial fibrillation, increased coronary artery calcifications and pathological cardiac remodeling.

At the same time, the organization RunningUSA has predicted that the number of recreational endurance exercise participants will continue to rise and age, presenting cardiologists and sports medicine physicians a unique population to manage.

Massachusetts General Hospital’s Aaron L Baggish, MD, director of the Corrigan Minehan Heart Center Cardiovascular Performance Program, coauthored a recent review on the controversial issues in Current Atherosclerosis Reports.

In the Copenhagen City Heart Study, researchers found that strenuous joggers had mortality rates like non-joggers, while moderate joggers showed improvement in mortality rates. However, the number of strenuous joggers evaluated in the study was extremely low—36 out of 1098.

In other studies, researchers have found an association between high levels of endurance exercise and atrial fibrillation. One study evaluating almost 53,000 participants linked atrial fibrillation with cross-country skiers.

While researchers have affirmed the association between long-term strenuous endurance exercise and atrial fibrillation, the potential mechanisms that would explain the association continue to elude them. In addition, prognosis and effective management data are lacking, and no precise exercise dose threshold has been established.

Recent data have suggested that an association exists between chronic high doses of endurance exercise and corollary right ventricular maladaptation. However, the numbers of participants in these studies were very low.

Other recent studies have drawn links between extreme exercise levels and increased coronary artery calcification, but that set of research continues to lack clarity and involves small and primarily observational data sets.

The review calls for clinicians who care for highly-active patients monitor these controversial issues while recognizing the limitations of some of the data. Clinicians can establish an open dialogue with patients and collaborate on decision making regarding exercise and cardiac issues.

The review also calls for the establishment of large registries specifically for strenuous exercisers that would lead to better characterization of “the complicated behaviors of aging athletes,” with data to include training habits, diet and other lifestyle attributes.

Refer a patient to the Massachusetts General Hospital Corrigan Minehan Heart Center


Cardiac remodeling criteria in athletes are under debate. Aaron Baggish, MD, and researchers propose defining it as exercise intensity and duration.