Mike Tindall looked exhausted in his latest Instagram post, telling followers "a little part of me died inside" as he took part in a sporty challenge for charity.
Mike told followers that he had been biking for five hours that morning, and was disappointed that he didn't get to stop for food, but he was still optimistic about the climb, telling viewers he was going to "let the good times roll".
The husband of the Queen's granddaughter, Zara Tindall, has embarked on a 770 km-long bike ride from Lake Geneva to Antibes to raise money for the charity Cure Parkinson's.
He is a member of a team of 22 riders, five of whom have been diagnosed with Parkinson's.
WATCH: Mike Tindall admits "a little part of me died inside" as he takes part in charity cycle ride
READ: Mike Tindall pleads with fans ahead of life-changing experience
The challenge, which is called Raid Alpine, lasts six days, and will see the former professional rugby player do a whopping vertical ascent of 18,000m: over two times the height of Mount Everest!
PHOTOS: Zara and Mike Tindall’s cutest moments with their kids
Mike wasn't letting the strenuous work get him down in his latest Instagram post, however.
He celebrated after managing to climb the highest road in the Alps, Col d'Iseran, reaching the peak after a 48km ride.
But Mike wasn't feeling so jolly after day two of the challenge, when he had to climb the Col de Prez, which he described as a "horrible, horrible hill".
Mike’s father was diagnosed with Parkinson's disease in 2003, and since then the retired rugby star has worked to help the charity Cure Parkinson's to fund research of the disease.
He became a patron of the charity in 2018 and, in the past, he has hosted several fundraising events for the charity, including a Celebrity Golf Classic.
Mike Tindall takes a swing at the Celebrity Golf Classic he hosted back in 2019
In a video shared by the Cure Parkinson's, Mike opened up about why his work with the charity was so important to him.
MORE: Mike Tindall close to tears in video discussing dad's heartbreaking health battle
"My dad has had Parkinson's for 20 years," he began. "You know, it's been a tough road for him, especially in the last ten years and it's been great to put that funding into research.
"So everything that Cure Parkinson's does is purely about research. Their sole goal is to not exist. To stop, reverse and cure Parkinson's ultimately, it's something that because of having to watch my dad go through it, that's something I'm more interested in, the cure side of it than just living with it."
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