Anthony Joshua will go into his rematch against Andy Ruiz Jr £10,000 lighter after losing a bet with training-camp team member Jonathan Constant.
Joshua will bid to win back his back his WBA, IBF and WBO heavyweight titles when he meets Ruiz Jr for a second time in Saudi Arabia on December 7.
Ruiz Jr pulled off one of the biggest shocks in boxing history when he stopped Joshua back in June after knocking the Brit down four times.
But Joshua's team looked in relaxed mood in a video posted from their training camp, which showed Constant trying to complete 25 wide-grip pull-ups in response to a challenge from the former Olympic boxing champ.
According to a tweet posted by TalkSport's online boxing editor Michael Benson, Joshua didn't believe that his friend and backroom team member Constant could complete the quarter-century of pull-ups - and bet him £10,000 he couldn't rise to the challenge.
The video shows Constant sail through the pull-ups at first, before tiring and then putting in a herculean effort to complete the 25th rep with the massive cash prize at stake.
After successfully completing the challenge, he can be seen being congratulated by team members while Joshua laughs, with cheers heard in the background.
Twitter users responded to the video saying the camp looked in happy and confident mood ahead of next week's huge rematch.
And Joshua himself is feeling confident ahead of the bout.
The 30-year-old told Sky Sports : "Apparently I'm fighting the quickest hands and the best fighter in the division. So once I beat him I want everybody to bow to me.
"I'm confident that I know what I need to do now, and I've prepared to the best of my capability to go out and perform. Performance leads to the win."
