William Sichel combated freezing temperatures at night and more than 100F during the day during the Across the Years 72-hour event in Phoenix.
The former cancer sufferer from Orkney clocked up 269.36 miles in three days – some 34 miles more than his nearest rival – after running virtually non-stop into the New Year.
But the event was mere preparation for his toughest race yet – to cover more than 567 miles in six days, the equivalent of running more than the distance between Edinburgh and Paris.
By completing more than 21 non-stop marathons, Mr Sichel will smash the oldest record in Scottish athletic history, set 126 years ago.
George Cameron, who was born in Edinburgh, pounded out that extraordinary feat in New York in 1882. Running under his professional name, George Noremac, the athlete, who was living in America, chalked up the astonishing distance on a purpose-built indoor track – cheered on by vast crowds – at the age of 28.
For his attempt at the Athens International Ultra Marathon Festival starting on 3 April, Mr Sichel, 55, a father of two, will be running on an outdoor cinder circuit used during the 2004 Olympic Games.
If he reaches 533 miles, he will set a new world record for his age group. His previous best over six days is 532 miles. But his main aim is to beat Cameron’s record.
Mr Sichel, who is just 5ft 5in tall, is the current world number two for his age over the distance. Weighing just 9st 2lb, he expects to lose more than half a stone in the race, an incredible proportion of his body weight.
The wool dyer has trained on the remote isle of Sanday, where he has lived for nearly 27 years.
His training regime includes running 60 miles a week with 12lbs of added weight, twice-weekly weight sessions – where he will squat twice his own body weight – 45-minute sessions in his 120F sauna, plus jogging for 45 minutes in the island’s swimming pool.
His diet is traditional Scottish food. Breakfast is porridge, followed by mid-morning snacks of oatcakes and cheese, a lunch of mince and tatties and for tea, muesli and fruit. He admits to three Kit-Kats a week and a pint of Guinness after a race.
“My ambition is to run over 600 miles in six days which has only ever been achieved by a handful of people,” said Mr Sichel, who runs an angora wool business on Sanday with his wife Elizabeth.
“After such a long race, I usually feel total fatigue but I do recover quickly. There is no prize money at stake in Athens, just pride and honour. But I hope to come back with George Cameron’s record.”
Mr Sichel – who started long distance running in 1994 – was diagnosed with testicular cancer 11 years ago.
Within a fortnight of having surgery he was back in training, and a month later he was fully fit and selected for the Great Britain team for the World 100km Road Championships.
“I am just an example of somebody who has faced big problems and got over them and kept going,” he said.
Geoff Wightman, chief eecutive of Scottish Athletics, said: “He is built on a different construction to the rest of us. His strength of mind and energy efficiency are amazing.”