(HealthDay News) – Marathon runners, particularly those who are less fit or less trained, may experience transient myocardial changes, according to a study published in the October issue of the Canadian Journal of Cardiology.

Valerie Gaudreault, MD, from Université Laval in Québec City, and colleagues 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.

The researchers found that, at peak training, runners exercised 8.1 hours and 62km per week, with mean maximal oxygen consumption (VO2max) of 53.2mL/kg/min. Global left ventricular and right ventricular ejection fraction decreased in half of the runners following the marathon. These runners had poorer peak training distance, training time, and fitness level. There was an association between change in global left ventricular ejection fraction and VO2max. There was significant correlation between segment decreasing function, decreasing perfusion, and developing edema, although myocardial changes were reversible at three months.

“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.”

Full Text (subscription or payment may be required)