Alan Shearer and Robbie Savage are tackling each other in a bid to be top of the bottoms in a Sport Relief challenge.
The pair are tackling a thigh-aching task to be the fastest to sit on half of the 90,000 seats in Wembley Stadium, which is expected to take five days of squatting and shuffling.
The football stars turned pundits will attempt the sit-off next month with each aiming to be the first to complete 45,000 chairs and reach the winning post, the royal box.
It has been estimated that they will have to manage around 14 seats per minute across ten hours each day to complete the challenge by the time the final whistle blows after five days.
Shearer Vs Savage: The Battle of the Backsides will raise money for the biennial charity event as they put their bums on the line and rack up a fresh seat every four seconds. The event will be punishing on their quad and glute muscles and they will have to face stiff, painful muscles as they keep going from March 10-14.
Match Of The Day star Alan said: "I'm used to being challenged at Wembley - I've played some crunch matches at this stadium and now I'm back to be tested again.
"Even at the peak of my career this challenge would have been tough on my body. However, now I am a retired footballer - so it's going to be a challenge of physical and mental endurance. I can't let Rob win; I'd never live it down."
Robbie - who appeared on Strictly Come Dancing in 2011 - said: "Alan does have an advantage as his butt is larger than mine - but my bottom is ready for the challenge.
"I've often watched Sport Relief and seen all the vulnerable people living difficult lives and really wanted to help to raise money for them - who knew it, would be my bottom raising cash.
"Wembley Stadium has always been kind to me when I played here during my career - let's hope lady luck is on my side for this challenge."
To support the challenge, members of the public are being encouraged to enter a competition at www.sportrelief.com/backsides with the chance to win tickets to see England play at the 2014 World Cup in Brazil, a day watching tennis at Wimbledon or a chance to see One Direction playing on tour.