A new discovery made by doctors studying intensive marathoners shows that when the body is pushed to its physical limit, the heart actually slows down. By measuring the heart rate of participants in a 90-hour bike climb swim paddle rope-a-thon -- before and after the race -- researchers were able to find that participants hearts slowed from 8 to 13 percent at the finish line. Recent studies have shown that heart patients should not run marathons, due to the adverse affects the extended physical strain can have on the heart. The heart can tire about ten percent -- and for those with a heart that pumps blood inefficiently, the effects can be detrimental. The study helped reveal more about the subtle changes that occur during extended, extreme physical exertion and the nature of heart failure.
