Heart risk for extreme cyclists?

Extreme endurance events including cycling and running can cause cardiovascular problems, a paper in the June issue of Mayo Clinic Proceedings says.

Although moderate exercise is encouraged by doctors, excessive exertion can risk problems including atrial and ventricular arrhythmias, coronary artery calcification and diastolic dysfunction.

Endurance sports, including professional cycling, have been associated with up to a fivefold increase in the prevalence of atrial fibrillation, the Mayo report said.

It is thought that structural changes that occur in the heart during extreme exercise can cause a buildup in scar tissue over time.

“Physical exercise, though not a drug, possesses many traits of a powerful pharmacologic agent,” James H. O’Keefe, MD, lead author of the Mayo Clinic Proceedings report and a cardiologist at Saint Luke’s Hospital of Kansas City, told the American Medical Times.

“However, as with any pharmacologic agent, a safe upper-dose limit potentially exists, beyond which the adverse effects of physical exercise, such as musculoskeletal trauma and cardiovascular stress, may outweigh its benefits.”

These health scare stories regularly do the rounds, but it’s worth noting that moderate strenuous exercise, most days of the week, is almost universally endorsed by doctors for health and longevity, and outside of pro cycling even the most competitive of riders would struggle to rack up the miles required to damage their hearts.