Sometimes we ARE what we eat.  ...Or at least, it helps.

In fact, the study shows that chocolate could boost indurence levels by 50%.

As reported last week by the New York Times Well blog, scientists at UCSD fed a group of middle-aged, inactive male mice a twice-daily dose of purified liquid epicatechin, the flavanol that is cacao's primary nutritional ingredient. A control group was given equal doses of water. Each group of mice was then divided in half, with one half of each group taking light daily strolls on the treadmill, while the other half of each group remained sedentary. At the end of 15 days, all of the mice took a treadmill test, running to the point of exhaustion. The study found that the animals that had been given water throughout the study grew tired more quickly than those that had been given epicatechin. Even the mice that had trained with daily treadmill exercise but were given water showed less endurance than those mice that had received no training but had been given the twice-daily doses of epicatechin. The rodent champions were those that had received daily work outs and the purified epicatechin. On average, they were able to run 50 percent further than the control group.

Eating Dark Chocolate Could Improve Physical Endurance - Delish.com.