Excessive endurance training can be too much of a good thing, research suggests

Excessive endurance training can be too much of a good thing, research suggests: Micah True, legendary ultra-marathoner, died suddenly while on a routine 12-mile training run March 27, 2012. The mythic Caballo Blanco in the best-selling book, Born to Run, True would run as far as 100 miles in a day. On autopsy his heart was enlarged and scarred; he died of a lethal arrhythmia (irregularity of the heart rhythm). Although speculative, the pathologic changes in the heart of this 58 year-old veteran extreme endurance athlete may have been manifestations of "Phidippides cardiomyopathy," a condition caused by chronic excessive endurance exercise.