Between miles 20 and 21 of the Boston Marathon, runners must climb the infamous Heartbreak Hill—over one-half mile of steep incline. Research shows that around the 20 mile mark marathoners began to exhaust the stores of energy in their muscles. For this reason, Heartbreak Hill is positioned at the worst possible point of the race. Just when runners are hitting their peak of physical fatigue, they find themselves staring up ...   more »