Simon French is completing a challenge every day for 30 days in honour of 'Fred Bennett's Don't Look Down' fund for research into acute lymphoblastic leukaemia.
Fred was 14 when he died in May last year.
Now supporters are joining forces to help Simon smash his original target for the charity.
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Simon said: "I came up with the idea of the 30 day challenge a while back and decided to make it as accessible as I could to anyone that fancied giving it a go.
"Basically, you decide whether you complete something 10, 20 or 30 times in 30 days. It can be the same thing every day, or different things on different days. It honestly doesn't matter, all you need to do is just commit to it and see it through to the end."
Simon has been completing 30 Murph workouts in 30 days. Murph is one of the most famous CrossFit workouts and involves a one mile ruyn, 100 pull-ups, 200 press-ups, 300 air squats, and a mile run to finish - all while wearing a 10kg weighted vest.
"The son of one the members at Imperial Bodies Gym Daventry where I train and work at was best friends with Fred," added Simon.
"It's a stark reminder that we should all live our lives every single day to the best of our ability as no-one knows what's round the corner.
The challenge ends on Monday, June 21.
"The support from the members at the gym and my wife Dawn at home has been unreal," added Simon.
"And despite having a few wobbles it’s been largely due to the combination of both that I’ve kept it together and finished each day."
He thanked all his well-wishes and supporters for helping to keep him going.
Fred was 13 when he was diagnosed in July 2019 he was diagnosed with ALL, a cancer of the blood.
His mother, Louise, said: "From the day Fred was born he lived at full speed. He wanted to go higher, faster, with extra danger. He hated to sleep, never sat still and could always be found conjuring up elaborate plans with his friends. Life was one long episode of Wacky Races."
When he began to feel tired and was off his food, his family thought it was typical changes for a teenage boy.
She said: "He had recently broken his shoulder in an ill-advised rugby tackle so we thought he just needed rest. When his glands began to swell, we suspected glandular fever and took him to the GP, who recommended a blood test to confirm. Within hours, we were in A&E being told that it was leukaemia. He was immediately transferred to Birmingham Children’s Hospital to begin his treatment."
At the end of the first six-week block of treatment, he still had leukaemia in his bone marrow when it should have been clear. He was moved on to a stronger course of treatment but this was still not effective. In November, he began preparation for a stem cell transplant but it was impossible to get his disease level low enough. Standard chemotherapy wasn’t enough and a new immunotherapy drug caused severe side effects which took him to intensive care, and had to be dropped.
Louise added: "Early in 2020, as his leukaemia was refractory (not responsive to chemotherapy) he became eligible for Car T-cell Therapy, a new form of treatment that used the body’s own cells. They are taken out, transformed in a lab, and then put back to fight the cancer. Even though there were complications along the way, including a seizure and a positive COVID diagnosis, we continued to be hopeful that this treatment would work where chemotherapy had failed."
Fred spent his 14th birthday in Great Ormond Street Hospital preparing for the cells to be given back to him.
"However, his doctors wanted us to be realistic," Louise said.
"The chemotherapy they had used to keep the leukaemia at bay had not done very much and his levels were dangerously high and they had to tell us that his chances of survival were very small. When asked if he had any questions, Fred asked when he would be well enough to go swimming."
Fred died on May 3, 2020, shortly after he had received the Car T-cells - nine months after diagnosis.
Louise said: "We have set up the Don’t Look Down Fund in the hope that more children will get the chance to live the life they deserve. We chose the name as to encompass Fred’s fearless and risk-taking attitude as well as conveying how difficult the whole journey is. Despite everything, Fred was determined to be as active, strong and risk taking as ever, and one thing that really stood out during his illness was his mental resilience and determination. He was adamant he could still do the things he enjoyed. His determination and positive outlook kept us going and made a huge difference to how we look back on his last year."
The money raised will fund research into finding new cures and treatment plans for refractory ALL.
Louise said: "We hope that we will all find risky and adventurous things to do to raise money in his name."
To make a donation to Simon's fundraising challenge, visit https://bit.ly/30daysforfred