Long-term high-intensity exercise linked to higher heart risks in athletes 35 and older
People age 35 and older who engage in years of sustained high-intensity exercise face a higher likelihood of certain cardiovascular conditions, according to new international research involving Radboudumc. The findings also prompted updated European and American cardiology guidance aimed at improving care for middle-aged and older competitive and endurance athletes.
Researchers report increased rates of heart rhythm disorders and coronary artery calcification among athletes with at least five to 10 years of very intense training. The study focuses on “Masters athletes,” including recreational and elite endurance participants in sports such as cycling, triathlon and marathon running.
“Exercise is healthy, but athletes are not immune to cardiovascular disease,” said exercise physiologist Thijs Eijsvogels of Radboudumc.
The research defines high-intensity exercise as activity that raises heart rate and breathing so significantly that normal conversation becomes difficult.
“It is about very intense exercise,” Eijsvogels said. “Sport where your heart rate and breathing go up significantly, where you can no longer have a normal conversation.”
At the same time, researchers emphasized that exercise remains broadly beneficial. The Dutch Health Council recommends at least 150 minutes of moderate-intensity activity per week. “Sport is in principle healthy,” Eijsvogels said. “It lowers the risk of premature death and of many chronic diseases.”
He added that the greatest health gains occur when inactive people begin exercising, and that benefits peak at around three to five hours per week.
“If you exercise between three and five hours per week, you reach your maximum health benefit,” Eijsvogels said. “Beyond that, it doesn’t yield much more.”
Researchers say evidence suggests a point exists at which increasing intensity and duration may bring diminishing returns and added risk, though the threshold remains unknown. “But where exactly that tipping point lies, we do not yet know,” Eijsvogels said.
The biological reasons behind the increased risk are still not fully understood. The most commonly identified conditions in highly trained athletes are arrhythmias and calcification of the coronary arteries.
Cardiovascular disease in athletes may also present differently than in the general population. One key warning sign is an unexplained decline in performance.
“In addition to typical complaints such as chest pain or pronounced shortness of breath during exertion, a sudden, unexplained decline in athletic performance can be a sign of coronary artery calcification,” said cardiologist Guido Claessen of Jessa Hospital in Hasselt, Belgium.
Researchers also warn that standard risk factors such as high blood pressure or elevated cholesterol are often underestimated in athletes because of assumptions that fitness offsets risk.
“It is often thought: but you are an athlete, you cycle every week, you are preparing for a marathon. You compensate for it with your healthy lifestyle,” Eijsvogels said.
He urged athletes and physicians to take these indicators seriously. “And if they are elevated, do something about it and don’t bury your head in the sand,” Eijsvogels said.
The findings helped inform new guidelines developed by European and American cardiology associations to improve detection and treatment of heart disease in Masters athletes. The effort was led by Eijsvogels and Guido Claessen, with participation from international experts. The guidance emphasizes shared decision-making between physicians and athletes, balancing medical risk with training goals.
“The guideline encourages shared decision-making between the physician and athlete,” Eijsvogels said. “Together, they review possible treatment options, considering not only risks, prognosis, and symptoms, but also the athlete’s personal goals. It’s not about giving a black-and-white recommendation, but about tailored care.”
The guideline also notes that symptoms may differ in athletes and can include performance decline rather than classic chest pain or severe breathlessness.
The number of people participating in endurance events such as marathons, triathlons and cycling races has increased significantly in recent years, raising questions about whether there is an upper limit to the health benefits of exercise.