Marathons take a heavy toll on the body, and even for peak athletes there’s been concern about stress on the heart after 26.2 miles. After all, the first marathoner dropped dead after finishing the course in Ancient Greece.

“For years there has been a recurring concern that training for a marathon is beneficial, but the marathon race itself might acutely stress the heart in potentially harmful ways,” Johannes Scherr, MD, a sports medicine specialist at Balgrist University Hospital in Zurich, Switzerland, told Medscape Medical News.

Now Scherr and his colleagues have found that, while the heart shows some evidence of impairment right after a race, it quickly heals. And there are no long-term negative effects after 10 years of repeated participation in marathons by male recreational runners. The study was published on December 10 in JAMA Cardiology.

Long-Term Follow-Up

The new study, known as Pro-MagIC, was a 10-year follow-up to the 2009 Be-MaGIC study, which looked at how nonalcoholic beer could reduce inflammation in marathon runners.

Researchers followed up with 152 of the 277 original participants to see whether repeated marathon participation is linked to long-term impairment of the right ventricle — and whether it could be predicted by post-marathon release of troponin T, a common biomarker of cardiac injury.

They found right ventricular (RV) ejection fraction (EF) declined significantly from a median of 52.4% to 47.6% immediately after and was 50.7% at 1 day after the race. Within 3 days they recovered and remained healthy after 10 years.

Small but statistically significant long-term changes occurred in left ventricular (LV) systolic and diastolic indices over time. At 10 years, LVEF decreased from 59.6% to 57.6%. The ratio of early diastolic mitral inflow to early diastolic mitral annulus velocity measured at the lateral wall, as an index of LV filling pressure, increased from a median of 5.1 to 5.4. However, both remained within normal limits.

Researchers also found no association between exercise-induced troponin T increase after the race with right or LVEF changes after 10 years.

“Marathon running caused an acute, measurable drop in RV systolic function, but this was transient and did not translate into long-term RV deterioration over 10 years in most recreational male runners,” said Scherr. “I was happy to see these reassuring long-term results.”

The study has a few important limitations, according to Scherr. First, he and his colleagues only looked at white male runners — a legacy of the original Be-MaGIC study, which excluded women to avoid physiological confounding from sex-hormone cycling on several measured parameters.

Therefore, the specific findings cannot be generalized to female runners, though Scherr expects the overall pattern would be similar. In addition, because the researchers were not able to follow up with every original participant, they cannot rule out that some may have experienced cardiac events in the intervening years.

Jonathan Kim, MD, director of Sports Cardiology at Emory University in Atlanta, said the long-term follow-up makes this study particularly interesting and important. The results add useful data to an ongoing debate in sports physiology about the long-term effects of elevated troponin T after exercise on heart function.

“The majority of us had felt that the findings of cardiac fatigue were really an acute response to marathon running but not a dangerous pathologic sequelae,” said Kim, who was not involved with the study.

The findings put a damper on the controversial idea that prolonged endurance exercise might permanently alter the heart and lead to exercise-induced arrhythmogenic right ventricular cardiomyopathy, he added.

“It supports the idea that if this entity exists it’s certainly not rampant, or a common sequelae, for people who run marathons,” Kim said.

Scherr and Kim reported no relevant financial relationships.

Brian Owens is a freelance journalist based in New Brunswick, Canada.