Running 100 miles should be easier than pounding out 200, but a recently released study in the journal PLOS One suggests that longer races may be less fatiguing and damaging than their shorter counterparts.
Researchers tracked 25* male runners as they took place in the Tor des Géants, a race consisting of 24,000 meters of elevation change across 300 km of travel. Before, during, and after the race, researchers took blood samples from the runners (looking for markers of inflammation and muscle breakdown) and tested how much force their muscles could produce.
Compared to a group of runners competing in races a quarter to a half as long, the Tor des Géants racers showed less muscle damage, fewer inflammation markers, and less-altered neuromuscular function.
It's paradoxical, but longer races may actually be easier—in some respects—on the body, the study authors note, though the explanation is a bit of a letdown: In the longest of races, runners move at a lower intensity, leading to less damage.
"The pacing strategy (i.e. slow pace from the beginning of the race) and sleep deprivation that result in very low-intensity concentric/eccentric contractions preserve the neuromuscular function despite the apparent extreme difficulty of this event," the study authors wrote.
*Only nine runners completed the race and were available for testing at all three times.