They are considered some of the top athletes of our time, those who can endure the grueling hardship of a 25 mile run, a 150 mile bike ride, or a 5 mile swim. They are our marathoners, triathletes, and long distance cyclists. Their bodies are finely tuned machines enhanced to accomplish one task: get from point A to point B as fast as possible by whatever means is at their disposal. However, a recent study suggests competing in these extreme endurance contests, and the chronic training associated with them can cause structural changes to the heart and large arteries, leading to myocardial injury (injury to the muscular tissue of the heart).