Belfast sexton Tate on top of the world after gruelling Everest race
For most people it's a once in a lifetime experience.
But, incredibly, one Northern Ireland man is in the final stages of training for his second Everest Marathon - having completed the first a decade ago.
What is even more remarkable is that Ken Tate, who is a sexton in St George's Parish Church in Belfast, only took up running when he was in his 40s.
Ever since he did his first marathon on his 50th birthday, he's been running city marathons, adventure races and ultra-marathons around the world including Mongolia, Mali and Madagascar.
After completing the Everest Marathon for the first time in 2007 Ken vowed never to do it again. But he is now fully committed to this year's gruelling run on November 27.
"To me it was a once in a lifetime experience, but then the opportunity came up again this year and as it is the last chance I will have to take part [there is an upper age limit] I decided to apply," said Ken, who heads off on November 6.
"I also felt that this would give me the opportunity to contribute something to Nepal, particularly after the earthquakes."
There have been 16 Everest Marathons since the first one was held in 1987.
The race starts at Gorak Shep at 5,184m, close to Everest base camp, and finishes in Namche Bazaar at 3,446m.
But the race itself - a 26.2 mile route taking in varied terrain, with boulders, sandy scree, stone staircases, forest trails and exposed paths - is the easy part, according to the Belfast man.
"The difficult part of the whole endeavour is getting to the start line in good health," Ken continued. "That's why we spend so much time trekking in. It is critically important that we are properly acclimatised.
"This time round I have a good idea of what's involved which makes what I am attempting to do even more lunatic!"
Weather may also be an issue. There is likely to be snow and ice at the start of the course - indeed, there was a blizzard in camp the night before the 2007 race, but Ken said a senior Sherpa took the decision to allow the race to go ahead despite that.
He explained: "It was -5 degrees when we started at 6.30am but was up to 25 degrees when we got down to the finish."
In order to acclimatise naturally to the high altitude, each competitor must take part in a 15-day trek in the Everest region under medical supervision.
He is currently running 100km a week with a weekly long run of 30km "mostly in places like Black Mountain and Cave Hill and other off road paths".
Ken anticipates the Everest race will take him at least twice as long as a normal marathon.
"It is a long, long race along terrain that goes up and down, up and down. I think it will take me around eight hours," he added.
"In 2007 I was running with a broken shoulder and this slowed me down a little.
"This summer I stayed well away from motorcycles, push bikes and skis..."
Anyone who wants to sponsor Ken online can visit www.virginmoneygiving.com/kentate or make a donation at St George's Parish Church, High Street, Belfast