Mountaineering
Grunsfeld appeared on the PBS NOVA episode "Deadly Ascent", which showed him climbing Mount McKinley, the highest peak in North America, in June 2000. Grunsfeld, along with Dr. Howard Donner, (a consultant to NASA) conducted research into the effects of body temperature at high altitudes by using internal thermometers swallowed in pill form. He was able to climb to an altitude of 17,200 feet before acute altitude sickness forced him to turn back.
In June 2004, Grunsfeld returned to McKinley while on vacation from NASA and successfully led a team that summitted. He is the only astronaut to have climbed all the way to the top of Mount McKinley.
Read more about this topic: John M. Grunsfeld