Only 15 runners have completed the Barkley Marathons in the event's thirty year history. The 100 mile course is one of the most gruelling running events imagined.
Set in Tennessee, the course is unmarked and climbs an accumulative 16,500 meters through treacherous terrain. The application process is a secret yet each year there are hundreds of hopefuls clamouring for one of the 40 spots.
Marathons, it seems, are no longer impressive. Kudos is only given to those able to run extreme distances, preferably over one hundred miles in an extreme place. The popularity of ultra-marathons has exploded with more than ten times as many races globally this year as there were a decade ago. Ninety four of those races take place in UK but there's also one in Antarctica if that's more of your thing.
The Muskathlon goes further, it's not just an extreme event in an extreme place, but there's an extreme fundraising target attached. Tim mountain-biked 106km in Jordan in 2017 and raised a whopping £19,000 for the charity Open Doors. The race started in the cool of the morning but the temperature quickly rose to 38 degrees centigrade in the shade.
"The race itself was so emotional and challenging. All that training and fundraising," Tim said. "I wept with joy and relief at the end and then threw up."
It definitely takes a certain character to take on the Muskathlon. Tim said that of all the participants that year, he was the least ill afterwards. Many were thwarted by the heat and sheer exhaustion of the challenge.
What if you want to take on a sponsored challenge that makes a difference but you're put off by the intensity of them? What then?
Koffi, a trainee teacher, said, "I'm not good at baking or running, but I can walk." So he set out on a 136 mile pilgrimage and raised more than £2,000 for Open Doors.
"It was difficult because it was the whole day of walking, but at the same time it gave me time to think, pray and enjoy creation."
Jesus himself walked most places and he rarely seemed in a hurry.
When Lazarus and Jairus' daughter died he lingered before going to them. The Bible talks a lot about taking time out and seeking peace; Psalm 46:10 says, "Be still and know that I am God."
For centuries Christians have done just that and walked pilgrimages as a spiritual discipline and time of reflection. Extreme challenges encourage you to go full speed and exhaust all your energy. But pilgrimages allow you to slow down and reenergise mentally and spiritually.
A 136 mile walk is certainly a challenge. But I would assume that so much countryside, quiet and time for reflection is a challenge too. We're so used to going fast and rushing from places and things that stillness is often foreign. It takes a very different discipline to focus your thoughts on prayer and God while walking for the suggested two weeks it takes to complete the pilgrimage.
Could a pilgrimage be the antidote to extreme fundraising? It certainly is a challenge, physically, mentally and also spiritually. But will the fact that the challenge builds you up instead of tearing you down by pushing you to your limits stop people sponsoring you?
Do people only donate because they long to see you suffer? Is that why there's been a surge in extreme events?
When I look back to my school days, all the fundraising challenges involved leg waxing and head shaving. Pain and humiliation were apparently very in.
Fundraising and giving is now so easy and convenient compared to 10 years ago thanks to a multitude of platforms like Kickstarter and Just Giving. Some organisations saw a 40% increase in donations when they started using giving sites.
It seems the convenience of fundraising has removed one it the biggest hurdles - actually getting the cash.
Donations are flooding in for millions of great causes - some odd and niche - every day. Movember started because two men wanted to see if they could bring the moustache back into fashion. The charity has now raised $837 million over 15 years.
According to event organisers, most people donate to support you – not because of the challenge itself or even the cause.
If like Tim you want an impressive feat that will test you physically and emotionally then go for it.
But if PE was never your forte, don't be daunted by the 'ultras' and 'extremes'. You can take on a gentle challenge while fighting for a vital cause and your friends will still donate.
If you want to put yourself through the Barkley Marathons for a good cause then go for it. But fundraising does not have to be extreme. If two weeks reflecting and walking along a chalk ridge with beautiful views of the gently undulating hills appeals most, then go ahead and challenge yourself.