Yahoo News reports on a recent study by Dr. Francois Carre of the Centre Hospitalier Universitaire de Rennes, France, which found that almost all cyclists competing in the Tour de France had enlarged hearts. The size increase was on the order of 20-40% larger than normal! He thought it would interesting to see whether the cyclists’ hearts are large to begin with or expand to accomodate the rigors of training (probably both). A bigger heart translates to more blood-pumping ability which in turn translated to increased oxygenation of blood and tissues.
In his study, Carre tracked seven former professional cyclists through their final year of competition and three years of retirement. Once a year, the cyclists took tests to check the size and function of the heart. They were also tested on their fitness levels. Carre found that the athletes’ hearts shrank nearly a quarter in size after they finished riding professionally. Still, the cyclists remained in excellent physical condition.
“Some athletes have a genetic predisposition to perform better,” Carre said. “But we found that in these cyclists, their hearts adapted to the hard training conditions by just getting bigger.”
While this study is not yet published (it was presented at a meeting), a quick PubMed search on the author yielded another interesting paper he’d published on the topic, “Sports-Specific Features of Athlete’s Heart and their Relation to Echocardiographic Parameters” published last year. Carre noted that the extent to which the heart’s left venticle changed depended upon the sport the individual was involved in (graph below, by sport).
In Carre’s rating system, the lower ranks corresponded to larger cardiac dimension, so in this case swimmers showed both the largest ventricular diameter and septal thickness. In general, athletes participating in endurance sports were found to have increased diameter and thickness, and the levels of these changes were benefical and not at all harmful.