Danny John-Jules collapsed during intense "Strictly Come Dancing" training.
The "Red Dwarf" actor fainted last Friday (19.10.18) while rehearsing the jive with his professional dancing partner Amy Dowden ahead of last weekend's performance, but they went on to score 37 out of 40 for their jive.
The 58-year-old star said: "It's cardio, fitness. I haven't moved like that since a long time. You worry about slowing down and if you slow down it's a bit of a no-no.
"I did collapse after the second run, the tech run on Friday.
"The floor manager looked down at me looking up at the ceiling and asked me, "Do you want to do another one?" "
But Danny's effort clearly paid off because their jive saw the pair score the first 10 of the series as they topped the leaderboard.
The "Death in Paradise" star took a whole day to process the judges" reaction to their dance.
He said: "It was all a blur. When I finished, I looked at Amy and only then I realised it had been good.
"I was still in a daze when I got to the judges and it didn't sink in until a day later when all the messages started coming in from social media."
Amy praised her partner ahead of their American Smooth this weekend, admitting he has "done really well" with the steps and lifts.
Speaking on spin-off show, "Strictly: It Takes Two", she said: "We're still working on the lifts but Danny has done really, really well. He hasn't dropped me yet.
"At the end, Danny won't be leaving the dancefloor in a normal way."
Danny and Amy received a standing ovation for their performance over the weekend, and judge Darcey Bussell described their routine as "extraordinary".
She said: "I have to get up and applaud you, that was extraordinary. The precision of your feet. The stretch of your foot on those kicks and flicks."