Too Much of a Good thing

Almost nothing in medicine enjoys the consensus that exercise does. It lowers the risk of heart disease, diabetes, several cancers, dementia and premature death. It is, as close as we have, a master lever for compressing the years of disability at the end of life into the smallest possible window - the very definition of healthspan. BUT....

Can You Exercise Too Much?

What the hearts of lifelong athletes reveal about the rest of us

Picture a man in his sixties who has run more than a hundred marathons. His resting heart rate sits in the low forties, and his fitness rivals that of someone half his age. Yet his heart scan shows coronary arteries studded with calcium, the kind of result doctors usually associate with heavy smokers.

On paper, his heart looks diseased. In life, he’s one of the fittest people in the room. That paradox sits at the centre of one of the most hotly debated questions in longevity science: can you exercise too much?

The case for concern

Exercise is about as close as medicine gets to a master lever for healthspan. It lowers the risk of heart disease, diabetes, several cancers, dementia and early death. The debate is only about the far edge of the dose-response curve: ultramarathoners, lifelong triathletes and masters cyclists still racing in their seventies.

In this group, researchers have found some surprising signals:

•         More coronary calcium, not less, than sedentary men of the same age

•         More plaque overall, according to Belgium’s Master@Heart study (2023)

•         Higher rates of atrial fibrillation, a common heart-rhythm disorder

•         Patches of scarring on cardiac MRI in some veteran competitors

Some scientists argue that the benefits of exercise plateau, and may even reverse, at the extreme end.

The case for calm

Others say these findings are real but are being misread. Athletes’ plaque tends to be densely calcified, which is the stable kind and less likely to rupture than the soft, inflamed plaque seen in sedentary people. Most importantly, no study has shown that highly trained athletes die sooner or have more heart attacks.

The largest dataset to date, a 2018 Cleveland Clinic study of more than 122,000 people, found no upper limit to the benefits of fitness. The fittest people had the lowest death rates of all. Low fitness carried a risk comparable to smoking or diabetes.

What it means for you

The dose at which any risk might apply is far beyond what most of us will ever reach. It means decades of high-volume, high-intensity endurance training, not your weekend parkrun, spin class or daily walk.

Even the cardiologists who study these athletes agree: the real public-health problem isn’t people exercising too much. It’s people barely exercising at all.

The lesson from the world’s most extreme athletes isn’t a warning. It’s an invitation. The real risk was never doing too much. It was doing too little.

Read the full feature, “Too Much of a Good Thing?”, in the 3rd edition of Live Thrive, out the first week of November.

This article is general information, not medical advice. If you have cardiac symptoms, a personal or family history of heart disease, or plans to start intensive training, please speak with a qualified clinician.