Masters at Heart
But the 2023 Master@Heart study challenged that assertion. It analyzed lifelong endurance athletes, late-onset endurance athletes (those who came to the game later in life), and healthy nonathletic controls. The study also found more coronary stenoses in lifelong athletes, but the breakdown of calcified vs noncalcified vs mixed plaques was the same across groups, thus contradicting the idea that exercise exerted its protective effect by calcifying and therefore stabilizing said plaques. The silver lining was fewer vulnerable plaques in the lifelong athletes (defined via high-risk features) but these were generally rare across the entire population.
Whether Master@Heart is groundbreaking or an outlier depends on your point of view. In 2024, a study from Portugal suggested that the relationship between exercise and coronary calcification is more complicated. Among 105 male veteran athletes, a high volume of exercise was associated with more coronary atherosclerosis in those at higher cardiovascular risk, but it tended to be protective in those deemed lower risk. In fact, the high-volume exercise group had fewer individuals with a CAC score > 100 (16% vs 4%; P =.029), though again, the vast majority had low CAC scores.
A limitation of all these studies is that they had cross-sectional designs, measuring coronary calcium at a single point in time and relying on questionnaires and patient recall to determine lifelong exposure to exercise. Recall bias could have been a problem, and exercise patterns vary over time. It’s not unreasonable to wonder whether people at higher cardiovascular risk should start exercising to mitigate that risk. Granted, they might not start running marathons, but many of these studies looked only at physical activity levels. A study that measured the increase (or stability) of coronary calcium over time would be more helpful.
Prior research (in men again) showed that high levels of physical activity were associated with more coronary calcium, but not with all-cause or cardiovascular mortality. But it too looked only at a single time point. The most recent study added to the body of evidence included data on nearly 9000 men and women and found that higher exercise volume did not correlate with CAC progression over the mean follow-up of 7.8 years. The study measured physical activity of any variety and included physically taxing sports like golf (without a cart). So it was not an assessment of the dangers of endurance exercise.
Outstanding Questions and Bananas
Ultimately, many questions remain. Is the lack of risk seen in women a spurious finding because they are underrepresented in most studies, or might exercise affect men and women differently? Is it valid to combine studies on endurance exercise with those looking at physical activity more generally? How accurate are self-reports of exercise? Could endurance exercisers be using performance-enhancing drugs that are confounding the associations? Are people who engage in more physical activity healthier or just trying to mitigate a higher baseline cardiovascular risk? Why do they give out bananas at the end of marathons given that there are better sources of potassium?
We have no randomized trials on the benefits and risks of endurance exercise. Even if you could get ethics approval, one imagines there would be few volunteers. In the end, we must make do with observational data and remember that coronary calcifications are a surrogate endpoint.
When it comes to hard endpoints, an analysis of French Tour de France participants found a lower risk for both cardiovascular and cancer deaths compared with the general male population. So perhaps the most important take-home message is one that has been said many times: Beware of surrogate endpoints. And for those contemplating running a marathon, I am forced to agree with the person who wrote the sign I saw during my first race. It does seem like a lot of work for a free banana.
Dr. Labos is a cardiologist at Hôpital Notre-Dame, Montreal, Quebec, Canada. He reported no relevant conflicts of interest.
A version of this article first appeared on Medscape.com.