Karl started running in the Wasatch Mountains during the summer of 1990. After running very little and winning a few mountain races, he was hooked. In 1996 he ran his first Ultra, the Wasatch 100.Two years later, he won the Wasatch 100 (his first ultra win) with a course record of 20:08. As of December 2007 he has won 48 ultras in 91 starts with 23 of those wins at the 100 mile trail distance.