My favorite Olympic moment of the 2010 Winter Games was the finish of the Womens 30 Kilometer Cross-Country Skiing event. Hard fought for 1 hour 30m and 33.7s. With only 0.3s between the gold medal winner, Justina Kowlaczyk, of Poland and the silver medal winner, Marit Bjoergen, of Norway, this was an Amazing Performance.
These athletes also left me puzzled. In the Avoiding Death By Exercise post, I raised doubts about whether the healthful benefits of endurance sports/training outweigh the negative effects.
A visible indicator of concern is the lack of muscle mass seen on marathoners. But, in these pictures, you see endurance athletes that do not lack for muscle mass, especially in their legs.
Is there something different about cross-country skiing or the way that cross-country skiers train that allows them to simultaneously excel on endurance measures and build / maintain muscle?