"Skyrunning"

YouTube link.

"If you think running a marathon is a feat in itself, imagine doing an ultra-marathon up a mountain. At "The Rut Mountain Race" in Big Sky, Montana, nearly 400 athletes from around the world gathered to compete across 31 miles. They cover more than 10,000 feet of elevation. The sport is known as skyrunning."

Posted for Skip, a friend up in northern Minnesota, who has competed in the Rut Mountain Race.  Awesome.