But Tommy Refenes has done it from the comfort of his front room in America.
When his sister launched a fundraising page to help their diabetic mum buy an alert dog, Tommy took it upon himself to walk some of the largest maps in gaming to help out.
His efforts ended with a six-hour stint on Grand Theft Auto V (GTA V) as he strolled across Los Santos.
Tommy, who is the co-creator of indy game Super Meat Boy, also spent two hours and nine minutes walking across the map of Red Dead Redemption and took four hours and 19 minutes to complete the length of Grand Theft Auto San Andreas.
Below the live stream of the fundraiser, the gamer wrote that his mum "is having a lot of trouble with her Type 1 Diabetes and an alert dog could help her out and improve her health tremendously".
He added: "The dogs are trained to recognise smells due to high and low blood sugar and alert their owner.
"Mom has lost the ability to do this on her own which could be potentially very dangerous for her.
"After 32 years of having diabetes, it's becoming almost impossible for her to tell when her sugar is going low or high. This is potentially a fatal condition."
Following Tommy's efforts the fundraiser page had broken the $15,000 (Â£9,307) target by $677 (Â£420) with 112 days remaining.
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Anna Lewis, 27, who lives in Fishponds, was last seen leaving Southmead Hospital on 13 April.
Avon and Somerset Police said they were increasingly concerned for her welfare and specialist teams were searching in north and central Bristol.
Ms Lewis is described as white, about 5ft 5in tall, of slim build, with brown eyes and long dark brown hair.
Det Insp Roger Doxsey, who confirmed foul play was not currently suspected in the case, thanked the public for their support and said all potential sightings are being followed up.
He said officers are concentrating on remote outdoor areas as Ms Lewis, who tends to wear her hair in a low ponytail, was known to go on camping trips.
She often wears jeans or walking trousers, hiking boots and loose jumpers.
Ms Lewis was reported missing on Friday by her family, who do not live locally.
Det Insp Doxsey said: "We are supporting Anna's parents and are keeping them fully updated on our inquiry as it progresses.
"We're also working with UWE Bristol and Southmead Hospital to try and find out as much as we can about Anna and her movements in the days before she went missing."
Most people associate a charity marathon with months of training ending in a gruelling test of endurance.
[NEXT_CONCEPT]
A trainee nurse who went missing from Bristol has been reportedly seen 10 times since a search for her began.