WATCH: Karl Meltzer on the Appalachian Trail

In the summer of 2016, Karl Meltzer set the speed record on the Appalachian Trail, covering the 2,190 miles from Maine to Georgia in 45 days 22 hours 38 minutes. His time was roughly nine and a half hours faster than the previous record, set in 2015 by Scott Jurek.

Meltzer is a seasoned ultra runner, with more 100-mile wins than perhaps any other runner to date, including the Wasatch Front 100 (six times), Hardrock 100 (five times), the Bear 100 and the HURT 100. But even for a veteran as experienced as Meltzer, the AT presents numerous challenges.

This video by Red Bull captures the sleep deprivation, terrain challenges and emotional toll of covering more than 2,000 miles in less than 46 days.

Watch the full film here.