Deputy Prime Minister John Prescott has sprained his ankle while running with youngsters at an athletics track.
Mr Prescott had expected to win the race
Mr Prescott, 67, told onlookers in Carlisle: "I've pulled a bloody muscle. I feel a right bloody twit."
Aides put an ice-pack on his swollen ankle before he limped away to his official chauffeur-driven Jaguar.
As he was led away, Mr Prescott, a schoolboy boxer, said of his 10 and 11-year-old competitors: "I thought I was going to beat these beggars."
He had managed to sprint only a few metres before pulling up.
Mr Prescott was in Carlisle for talks on how to regenerate parts of the city, damaged by floods in January last year.
Sir Menzies Campbell was no slouch on the track
He revealed: "I've been in the gym an hour every day. I feel a right bloody twit."
A spokesman for the Office of Deputy Prime Minister said: "He pulled a muscle, a mild sprain, he is going to be fine."
Despite his best efforts to get fit, the deputy prime minister is not among the foremost athletes to have entered Parliament.
Middle-distance runner Chris Chataway, who served as a pace-setter when Roger Bannister broke the four-minute mile in 1955, was a Tory MP from 1969 to 1974.
Jeffrey Archer, who represented the Louth constituency before becoming an author, was an accomplished sprinter while at Oxford University.
Sebastian Coe, who won the 1500m race at the 1980 and 1984 Olympics, was Conservative MP for Falmouth and Camborne from 1992 to 1997.
The current Liberal Democrat leadership contender Sir Menzies Campbell was no slouch on the track either, competing as a sprinter at the 1964 Olympics.