High‑intensity training: a new age caveat

For years, the public message about exercise has been almost comically simple: more is better. That is still mostly true. Regular exercise lowers cardiovascular risk and helps people live longer. But a new international cardiology statement says that for “masters athletes” — usually defined as adults 35 and older who train and compete well beyond standard activity targets — the story gets more complicated. These athletes are not protected from heart disease by fitness alone, and some abnormalities appear more often in them than in less active people (academic.oup.com, radboudumc.nl). That statement, published April 6 in the *European Heart Journal*, is not a warning to stop training. It is a recognition that sports cardiology has aged into a new problem. The first generation of people who spent decades doing marathons, triathlons and high-volume cycling is now old enough to show what long exposure to intense endurance work looks like in the heart. The joint document from the European Society of Cardiology’s preventive cardiology association and the American College of Cardiology focuses on seven trouble spots: atrial fibrillation, slow heart rhythms, ventricular arrhythmias, coronary atherosclerosis, aortic dilatation, myocardial fibrosis and exercise-related arrhythmogenic cardiomyopathy (academic.oup.com). The shift here is not just medical. It is cultural. Older guidance often treated heart findings in athletes as reasons to restrict sport. The newer American and European approach is built around shared decision-making instead. The 2025 AHA/ACC sports participation statement moved away from blanket “disqualification recommendations” and toward individualized discussions about risk, goals and ways to reduce danger. The masters-athlete consensus applies that same logic to people over 35 who may have coronary disease, atrial fibrillation or enlarged aortas but still want to train hard (heart.org, acc.org). What changed is the evidence base. One of the clearest concerns is coronary disease. A 2025 *European Heart Journal* review concluded that long-term, high-volume, high-intensity endurance exercise may be associated with more coronary atherosclerosis and coronary artery calcification, even though athletic activity itself has not been shown to raise the rate of clinical events. That sounds contradictory until you remember what the review is really saying: high fitness is protective, but it does not erase plaque biology. In athletes over 35, coronary disease remains the leading cause of sudden cardiac death, which is why the authors argue that traditional risk factors like blood pressure, cholesterol, smoking history and family history still matter enormously in people who look exceptionally healthy from the outside (academic.oup.com). The other concern is scar tissue. In July 2025, a British Heart Foundation-backed study of 106 asymptomatic male cyclists and triathletes aged 50 and older found that athletes with myocardial fibrosis were more than 4.5 times as likely to have an abnormal ventricular rhythm episode as athletes without scarring. A follow-up study published January 12, 2026 found that the athletes who developed ventricular tachycardia were not training more or harder than the others. Three quarters of them had heart scarring. That matters because it shifts the question away from whether one brutal workout is dangerous and toward whether years of intense training can leave behind tissue that becomes electrically unstable later on (bhf.org.uk, academic.oup.com, leeds.ac.uk). That is why the new guidance spends so much time on detection. In athletes, symptoms can look odd. Chest pain and shortness of breath still matter, but so does something more subtle: an unexplained drop in performance. Radboud University Medical Center, one of the groups behind the new consensus, highlights that a sudden decline in output during training can be a clue to coronary calcification in older athletes. Wearables may help, too, not because gadgets can diagnose disease on their own, but because years of heart-rate and rhythm data can reveal changes that would otherwise be dismissed as normal aging or overtraining (radboudumc.nl, academic.oup.com). So the new caveat is not that exercise becomes bad at 35. It is that extreme training stops being a simple proxy for cardiovascular safety. The people most committed to exercise may need the least generic advice: keep moving, treat blood pressure and cholesterol like they matter, pay attention to rhythm changes and performance drops, and do not assume that a marathon finish time can outrun a calcium score. The consensus statement’s target reader is the athlete who still looks indestructible at the starting line and the clinician who now has to ask a more useful question than “Can this person compete?” (academic.oup.com, radboudumc.nl).