People are being urged to show their support for thousands of competitors who will tomorrow take on a gruelling 20-mile obstacle course.
The Rat Race Dirty Weekend takes place for the third time in the grounds of Burghley House, near Stamford, on Saturday.
Competitors will either take on a 20-mile course featuring 200 challenging obstacles, or can opt for a shortern - albeit still challenging - 13-mile course with 150 obstacles.
Obstacles range from muddy trenches to huge wooden climbing frames, swimming in freezing water to impossibly long monkey bars, and competitors from across the country will descend on Stamford for the event.
In the evening, there will be music from indie band Ash and funk and soul DJ Craig Charles.
Many runners are taking part for charity.
Brian Makwana, from Castle Bytham, and a team of friends are running to raise money for CDH UK in aid of Brian’s son Wyatt, who was born with a condition called congenital diaphragmatic hernia.
Barry Newman, part of 16th Regiment Royal Artillery, based at St George’s Barracks in North Luffenham, will take part for the event’s chosen charity Children with Cancer UK.
And Paul Scholes, from Stamford, will be taking part in his third Rat Race for Histiocytosis UK in memory of his son Oliver who died in June 2012 aged two.
Organisers of the Rat Race Dirty Weekend are also hoping to break the Guinness World Record for the most people running in their underwear, which currently stands at 2,270, today.