Born with cystic fibrosis, a life-limiting condition that affects the lungs and other major organs, doctors initially gave Josh a 10% chance of surviving his first night due to complications. Then they said he would be unlikely to live past the age of 30.
But when he was two, his parents took him to America to see Dr Bob Kramer, who advised him to “run his legs off” in a bid to stay fit and healthy.
And this inspired Josh to do as much sport as possible, as he says, “how hard I train directly impacts how long I’m going to live.”.
At school, Josh stayed active and was part of the football, rugby and cross country teams.
And at the age of 17, he climbed Mount Kilimanjaro and had a boxing match with former European heavyweight champion Scott Welch at the 5,895-metre summit, raising £125,000 for CF charities.
But when he was 21, Josh was rushed to hospital with stomach pains and was told he had a lower chance of survival than he had been given at birth.
He prepared for the worst and said his goodbyes to his family, but survived after a seven-hour operation which untwisted his intestines.
When Josh defied the odds by turning 30, he celebrated by becoming the fifth person in the world to complete the World’s Fittest Man challenge. Then, in 2018 he went on to break a world record by lifting one million kilos in less than 24 hours, over double the previous record.
He has also taken on other ultra-endurance challenges, and in October this year he completed his latest - swimming the English Channel, cycling 200 miles to Twickenham and then running 160 miles home to Cardiff all in five days with no rest.
On top of this, Josh has raised more than £800,000 for CF awareness and has now set up his own charity, CF Warriors, to encourage children living with the condition to get into sport and exercise to increase their life expectancy.
The foundation has also provided a support system for children all over the world, who are isolated from meeting others with CF due to risk of cross-infection.
Josh is also an ambassador for Rays of Sunshine, a charity that brightens the lives of seriously ill children by granting their wishes.
Now 32, Josh says: “The reason I do these challenges is to raise awareness about CF. It’s to show kids who have it to pursue exercise and not give up on their dreams.
“It’s not just for those kids though, it can be motivation for anyone as exercise is so good for the body and for mental strength.”