The health benefits of exercise are limitless. Aside from helping people reach their weight loss goals, exercise has been shown to improve brain function and memory, treat Type 2 diabetes, and ease arthritis pain. There’s no doubt that regular bouts of exercise are healthy, but one cardiologist, Dr. André La Gerche, head of Sports Cardiology at the Baker IDI Heart and Diabetes Institute, argues that scientists have not adequately researched the negative side effects of too much exercise.

In a review published by the Canadian Journal of Cardiology, La Gerche says high levels of intense exercise may be cardiotoxic, promoting permanent and detrimental structural changes in the heart. "This paper discusses the often questionable, incomplete, and controversial science behind the emerging concern that high levels of intense exercise may be associated with some adverse health effects," Dr. La Gerche wrote.

Throughout the review, La Gerche raises important questions about exercise science and acknowledges often overlooked controversies in the field. For example, he cites the fact that most therapies have a dose-response relationship, whereby the benefits decrease at high doses and the risks of adverse events increases. He suggests this is likely true for exercise, too.

Heart attacks in athletes are usually attributed to underlying abnormalities in their heart structure or their predispositions to heart disease, but La Gerche questions if this is more likely due to structural changes in the heart from over exercising. He also questions if athletes are generally healthier individuals, not because they exercise more, but because they do not smoke or consume alcohol.

Overall, La Gerche’s review does not definitively state that over-exercising is a dangerous problem, but it urges the scientific community to conduct more comprehensive research in the field. In the paper, he attributes the numerous unanswered questions and controversies surrounding over-exercising to the fact that small, cross-sectional experiments that study over-exercising are often overshadowed by large population studies that are carried out to support the benefits of exercise

"The answers regarding the healthfulness of 'extreme' exercise are not complete and there are valid questions being raised," continues Dr. La Gerche. "Given that this is a concern that affects such a large proportion of society, it is something that deserves investment. The lack of large prospective studies of persons engaged in high-volume and high-intensity exercise represents the biggest deficiency in the literature to date, and, although such work presents a logistical and financial challenge, many questions will remain controversies until such data emerge."

Source: La Gerche A. The Potential Cardiotoxic Effects of Exercise. Canadian Journal of Cardiology. 2016.