Exercise is one of the best things we can do for a healthy heart. Yet research shows that endurance athletes have up to a four times higher risk of atrial fibrillation (an irregular or fast heartbeat) than non-athletes. This heart condition increases risk of both heart failure and stroke.

If regular exercise and being fit reduces our risk of many chronic diseases and preserves mental and physical health, why is it that people who are very fit face greater risk of a potentially deadly heart condition? Research suggests that when it comes to heart health, there may be too much of a good thing.

When we take a broad look at the evidence, it’s clear that exercise plays a key role in keeping the heart healthy and lowering risk of atrial fibrillation for most of the population.

For instance, an analysis of over 400,000 people found that those who said they did between 150-300 minutes of moderate-to-vigorous intensity physical activity per week had a 10-15% lower risk of developing atrial fibrillation compared to those who were inactive.

Higher levels of exercise may only be protective in females. The study also found that exceeding these recommendations by up to three times was further protective for females but not males, with around 20% lower risk of atrial fibrillation.

Exercise is also emerging as a cornerstone treatment for patients who already have atrial fibrillation. A meta-analysis my colleagues and I conducted showed that in patients with atrial fibrillation, exercise

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