Sir Steve Redgrave had to sit out the latest heat in Channel 4's winter sports show The Jump after doctors found he had cracked a bone in his hand.
The Olympic champion rower took a nasty fall as he trained for a cross-country skiing event but it was thought he had escaped with nothing more then bruised pride.
Sir Steve sat out last night's show while he was checked out and it appeared the damage was worse than first thought, which left him unable to take part in today's speed skating heat.
A spokeswoman for the show said tonight: "Sir Steve has bruised ribs and a broken bone in the back of his hand."
His failure to take take part in the skating challenge meant he was put into the bottom two and was then forced to take part in tonight's jump off.
Sir Steve gave medics a fright when he initially fell because he lay motionless in the snow for several minutes. But it later transpired that he had taken first aid training and had been told to remain still to avoid worsening any injuries that may have occurred. His sensible approach was commended by professionals today.
Clive James, training officer at St John Ambulance, said: "Sir Steve Redgrave was right to lie still when he feared he had a back injury. People's natural instinct is to try to get up straight away, so if you have sustained an injury, you could aggravate it by doing this.
"Take time to gather yourself together, give your body time to tell you if you have any injuries and if you think you have any pain or discomfort, especially in the neck or back, you should try to keep as still as possible until medical help arrives.
"This just shows the importance of learning first aid, and we hope others taking part in the Jump take Steve's lead. Extreme sports often result in dangerous situations, and first aid can often be the difference between life and death."
Participants in the show have suffered a number of injuries. Melinda Messenger withdrew after suffering concussion on the bobsleigh track and socialite Henry Conway broke a bone in his hand during training.
At the start of tonight's show, host Davina McCall asked Sir Steve why he was not in plaster despite having broken a bone, and he said: "I had to make a decision if I was going to still be on the show or have to leave the show. If I put a plaster on I can't jump, so I decided not to have the plaster on."
He said he "consulted with the doctor back home" - his wife - and said she was happy for him to carry on.
"I've had lots of injuries and lots of illness over the years and she's got me through all of them, so if I'm going to trust anybody it's got to be her," he said.
Sir Steve said he chose not to compete in the speed skating for fear of having a big fall and needing surgery on his finger.
"But the biggest problem is my ribs. I've got very badly bruised ribs, and that's what causing me more pain. The finger's nothing," he said.
Sir Steve said he slept in the cupboard last night as lying down was too painful.
"I wrapped myself up in the duvet and got into the cupboard and slept in the cupboard all night, so I could sleep standing up instead of lying down," he said.