You have to be the fittest of the fittest to have a chance at climbing Everest. Months on months of training, your body needs to be in peak physical condition.
But even former NRL grand final-winning teammates had to endure an experience that reminds us of our nightmares.
Alongside former Knights, Paul Harragon and Danny Buderus and joined by a group of 29 people including Rugby legend Steve Menzies, the party set off on a nine day trek raising money for the Mark Hughes Foundation.
But they were soon about to endure an experience they could have never prepared for.
"Some of the things that they've suffered, like, just before they got to base camp, they were dropping like flies," recounts Johns' wife, Trish, on Triple M's Grill Team. "They were just collapsing.
Despite Matty being in great shape, even the former half didn't go unscathed.
"He only got a little bit of altitude sickness towards the end. He had dizziness and he was coughing up blood. He's only told me that after they all back to Kathmandu."
Their aim was to raise 500,000 dollars, but the group ended up just shy, donating 448,125 dollars to the cause.
Hughes, a former knights star himself, was diagnosed with brain cancer in 2013. He started the charity to help others battling the same disease. On his website, he confirmed everyone made it back to Kathmandu sage.
"All the team have been powering along the track well, there's so much wonderful scenery and amazing twons and people along the way, you just don't know where to look," writes Hughes.