Based on the popular TV programme, fun obstacle courses were commonplace at charity and community events back in the day.
This gallery of colourful photos from our archives looks back at some knockout madness in the noughties – can you spot yourself or anyone you know?
1. Mallett fun
Pictured at Graves Park, Sheffield, where the It's a Knockout Challenge in aid of the Children Today charity was held. Seen is hst Timmy Mallett, of TV fame, with competitors - July 2008 Photo: Michael Waistell
2. Spectators
An It's a Knockout challenge was held in aid of the Children Today charity in July 2008. TV presenter Timmy Mallett attended - July 2008 Photo: Michael Waistell
3. Ready for action
The 'Ideas By Net' teams ready for action in the It's a Knockout Challenge at Graves Park in aid of the Children Today charity - July 2008 Photo: Michael Waistell
4. Giants
The St Luke's 'It's a Knockout Day' held at the HSBC Sports ground in Dore. The giants had to run over some ground sheets which were being moved by opposing teams and try not to fall over - July 2009 Photo: Sheffield Newspapers