HealthDay News — Marathon runners, particularly those who are less fit or less trained, may experience transient impairments in heart function, study findings indicate.

Although everything returns to normal after 30 days, adverse cardiac changes often occur in the two days following a marathon, with the most pronounced changes occurring in the least fit athletes, Valerie Gaudreault, MD, from Université Laval in Québec City, and colleagues reported in the Canadian Journal of Cardiology.

They prospectively studied 20 recreational marathon runners without known cardiovascular disease during peak training before, immediately after and three months after a marathon. Assessments included changes in global/segmental myocardial function, edema, resting perfusion and fibrosis.

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At peak training, runners exercised 8.1 hours and 62 km per week, with mean maximal oxygen consumption (VO2max) of 53.2 mL/kg/min.

The post-race evaluation showed that global left ventricular and right ventricular ejection fraction declined by more than 5% in half of the runners. Those runners did not run as far during their peak training, did not train as long per week and had a lower maximal oxygen consumption compared with the others.

Overall, 36% of left ventricular segments developed edema, 53% had function drop by more than 5% and 59% had decreased perfusion. Three months after the marathon, however, all measures returned to baseline levels.

“The changes are more widespread among those with lower fitness levels and less training,” a coauthor said in a statement. “Although no permanent injury was observed in this group of runners, the findings suggest that there may be a minimum fitness level needed beyond which the heart can bounce back from the strain of training and running a long race. Furthermore, these results emphasize the need for proper preparation before recreational distance runners engage in a marathon race.”


  1. Gaudreault V et al. The Canadian Journal of Cardiology. 2013; 29(10):1269-1276.