They were panting before they started, let alone at the end of the 5km race - but that might have had something to do with the huge blue Y-fronts the runners were wearing.
Men and boys donned the unusual underwear as they took part in Olympic athlete and triple World Champion Colin Jackson's first ever Sanlam Go Dad Run event in Norwich.
Bathed in today's glorious autumnal sunshine, the runners made their way through Eaton Park and helped to raise awareness of prostate cancer - as well as money for charities including Norfolk and Waveney's own Big C.
Mr Jackson, who started the raise and handed out medals to the winners, has been involved with the races since they were started in 2013.
He said: 'What we've tried to do is get men's health issues really into major focus. For me, I had two uncles who suffered from prostate cancer and one, unfortunately died and one survived.
'The one who survived was the one who was more vocal and talked about his problems straight away and we managed to save him.
'I think an event like this where you can get guys together to talk about and people who suffer from it realise they are not on their own, that will make a huge difference.
'It is an absolutely stunning day here in Norwich and I'm really pleased that so many people have turned up, not only just to run, but to support as well.'
One in eight men in the UK will get prostate cancer and, last year, Big C Centres had 1,017 visits from patients who had been diagnosed with prostate cancer.
The charity's Norwich and King's Lynn centres host support groups specifically for me affected by prostate cancer.
Clive Evans, Big C's director of income generation, said: 'Big C is there to support anyone affected by cancer and help people to get the best cancer care here in Norfolk.
'We are proud to be funding research into prostate cancer, as well as many other types, here in Norfolk, where advances are being made all the time.'
To find out more about the work which Big C does to improve the lives of those affected by cancer in Norfolk and Waveney, visit www.big-c.co.uk
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