Olympic medallist James Cracknell is being treated for a fractured skull after a cycling accident in the US.
He is in hospital in Phoenix, Arizona, where his wife Beverley Turner and children are at his bedside.
Cracknell was in the state filming for the Discovery Channel. He was due to attempt to set a new world record cycling from Canada to Mexico for a BBC series next month.
He was thrown from his bike after being hit from behind by a truck on Tuesday afternoon but is said to be making "good progress".
A statement issued by the Discovery Channel said: "James Cracknell was involved in a road traffic accident while cycling in Winslow, Arizona.
"James was taken to hospital where he is being treated for a head injury.
"He is conscious and his condition is stable; doctors have said he is making very good progress. His wife and family are with him as he continues to recover."
Cracknell has undertaken a number of TV challenges with friend Ben Fogle which have put his health at risk. He has rowed across the Atlantic and raced to the South Pole.
Fogle said: "My thoughts and prayers go to James and his family at this anxious time. Having spent many months in some of the toughest places on earth with him, I know how strong-willed he is and I'm sure he'll bounce back soon."
Fogle is flying out to visit him.