For runners, the twin axioms of "going the distance" and "slowly, but surely" can reap dividends. A new study shows that athletes who raced in the longest and perhaps most challenging ultramarathon in the world suffered less muscular damage than runners who raced in a quarter or half of the distance. The reason for this counterintuitive finding: a slower pace.

In the Tor des Géants, competitors cover more than 200 mountainous miles in the province of Val d'Aoste in the Italian Alps, dealing with elevation changes totaling nearly 15 vertical miles. Marathoners have 150 hours to finish the race, with the best doing it in around 80 hours. The runners stop to sleep for brief periods, but do so as little as possible, oftentimes moving through the night wearing headlamps.

Jonas Saugy, a sports physiologist at the University of Lausanne in Switzerland, and colleagues, conducted tests on 15 male runners in 2011 before and during the race, as well as about a half-hour after they crossed the finish line. The results were compared to those from other races, such as the previously studied 103-mile Ultra-Trail du Mont-Blanc. Blood tests revealed that the Tor runners had lower levels of inflammation markers including creatine kinase and C-reactive protein than runners in shorter races. Other tests involved electrical stimulation of knee and foot muscles to gauge fatigue. Again, Tor runners exhibited less loss of strength than Ultra-Trail du Mont-Blanc participants.

The saving grace for the Tor ultramarathoners, Saugy says, is the need to manage their pace. This works on both a conscious level to conserve energy early in the race and as an unavoidable side effect as the runners tire. Ultimately, the speed for Tor runners is relatively lower over the lengthy course than in shorter marathon events, and a lack of sleep helps keep it slow: "The sleep deprivation leads to a decrease of speed and intensity," says Saugy. "This is the real protective effect that involve less muscle damage and neuromuscular fatigue."