A new report may give pause to “amateur” marathon runners – that is, those who undertake the grueling endurance event without sufficient training.

Research just published in Circulation, Journal of the American Heart Association, found that running a marathon when you’re not ready can increase cardiac strain.

The findings

Investigators in Spain compared levels of cardiac biomarkers, including – troponin I and troponin T- in 21 groups of 3 runners each after each individually ran an endurance race of three different lengths – a full marathon, a half marathon and a 10K race. All of the 63 subjects were amateur runners. They also measured levels of biomarkers for cardiac tissue stress.

Although there was little difference in 10-year risk for cardiovascular events between the runners (average about 3 percent), the strain on the heart muscle, as measured by the biomarker levels, was much greater after a full marathon.

Who’s at risk?

The incidence of cardiac arrests in marathoners is only about 1 in 50,000 runners who compete in races, but a high proportion of all exercise-induced cardiac events occur during marathons, especially in men 35 years of age and older.

The number of subjects in the study was not large enough to accurately assess differences in 10-year cardiovascular risk, but the researchers are planning to examine this in a larger group of runners, said lead investigator Juan Del Coso, Ph.D., director of the exercise physiology laboratory at Camilo José Cela University, in Madrid, Spain.

Shorter races might be better

“We typically assume that marathon runners are healthy individuals, without risk factors that might predispose them to a cardiac event during or after a race. But with the growing popularity of long-endurance races, the exponential increase in the number of participants, and the lack of appropriate training in some cohorts of amateur runners, our findings suggest that running shorter endurance races might reduce the strain imposed on the myocardium during running competition,” Del Coso said.

Co-authors are Beatriz Lara, Ph.D.; Juan José Salinero Ph.D.; César Gallo-Salazar Ph.D.; Francisco Areces Ph.D.; Diana Ruiz-Vicente Ph.D.; and Manuel Martinez, M.Sc. Author disclosures are on the manuscript.

The Vice-Rectorate of Innovation of Camilo José Cela University (HEART project) supported the study.

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