From the video's description:

"After three years of planning and over 10 years of extreme unicycling Lutz Eichholz succeeds in the unicycle descent of the 5671m high Damavand in iran. Despite enormous problems with the high attitude, injuries in the team and weather fluctuations between 40° and -7° celsius Lutz Eichholz succeded in the record breaking mountain descent. Never before has a unicyclist attempted to descend such a high mountain. "At some points I felt so bad that I thought I would have to give up. However, this project is so important to me that I managed to push my limits further than expected“. http://lutzeichholz.de/damavand/"