Runners are limbering up ready for the Harefield Hospital Fun Run.
The 33rd annual event will take place on Sunday, September 1 and the application process is still open to would-be runners.
The three-and-a-half mile course starts and ends in the grounds of the hospital and participants can run as many laps as they wish.
The record was set in 1997 when a transplant patient ran 21 miles, only five miles short of a full marathon.
Lisa Muscutt had a double lung transplant at Harefield in 2007 and has taken part in the Fun Run several times over the last few years. She said: "After my transplant I never thought I would have been able to do anything like this, but the great atmosphere on the day and the sense of achievement you feel makes me want to keep doing it.
"For me, it’s also a way that I can give something back to the hospital that transformed my life by helping raise awareness of the vital work they do for people with heart and lung conditions."
Organisers say the run attracts up to 1,200 people of all ages and also offers entertainment including arts and craft stalls, an all-day barbeque, mini children’s races, tug of war, vintage cars, as well as a raffle and sports memorabilia auction.
Since the first Fun Run in 1981, led by the late comedian, Eric Morecambe, the event has raised over £900,000 to support a wide variety of projects at Harefield Hospital, as well as helping to fund research and treatments for heart and lung disease.
Entering the Fun Run costs £10 for adults and £5 for children, which includes a race T-shirt, medal and drink.