William Sichel, from the Orkney island of Sanday, has been taking part in the Self Transcendence race in New York, a 3,100-mile event which involves circling the same block a total of 5,648 times.
He flew out to America to begin the challenge, described as the longest certified footrace in the world, on June 15 and has been clocking up the miles ever since.
Mr Sichel, who is originally from England but has lived on Sanday for 30 years and competes under the Scotland banner, is eighth after 25 days.
He has pounded more than 1,422 miles on the course, which is just half a mile long and is opened between 6am and midnight daily.
The race is the longest certified accurate race in the world.
Before the event began, the block was certified by an official measurer as being 0.5488 miles long.
The runners have to circle this block more than 5,000 times. They average about 60 miles a day, to complete the race within 52 days.
It has been described by the New York Times as "the world's toughest footrace".
Mr Sichel hopes to follow the success of fellow expatriate Al Howie.
Mr Howie, originally from Saltcoats, North Ayrshire, was a leading multi-day runner in the 1980s and 1990s after emigrating to Canada.
He once took part in a 1,300 mile event, passing the target on day 24 of the race.
Mr Sichel continues to log 60 miles a day, and with every step is increasing the distance with the intention of finishing the 3,100 miles within the 52 day race cut off.
In 2010, Edinburgh GP Andrew Murray completed a 2,659-mile run from John O'Groats to the Sahara desert.
However, unlike Mr Sichel's efforts, Dr Murray's has not been empirically timed and measured.