The Philadelphia Marathon is back in 2014, and there are more than 50,000 spectators, 30,000 runners and 2,500 volunteers expected to descend on the City of Brotherly Love.
Listen to what a group of German researchers did in their efforts to study the impact marathon running has on the heart.
At first glance, endurance athletes are to be commended because they are trying to stay fit, but there is a down side.
When runners finish a big race, they usually get medals, each one a literal badge of honor. Some runners are donating their medals to young people going through cancer treatment.