British astronaut Tim Peake says he is feeling "great" a month after returning from his six-month mission to the International Space Station.
Getting back his sense of balance had been the most difficult part of readjusting back to gravity on Earth, said the 44-year-old father of two.
During his intensive rehabilitation programme, Major Peake has undergone brain and bone scans, donated muscle tissue, and had numerous blood tests as doctors investigate how his body is coping.
Speaking at the Farnborough International Airshow, he said: "I feel in great physical condition."
The astronaut was making his first public appearance in the UK since landing on the steppes of Kazakhstan in a Soyuz space capsule on June 18.
He said: "It still seems fairly surreal that less than four weeks ago I was on board the International Space Station travelling at 25 times the speed of sound and looking down on planet Earth."
Describing what it was like to readjust to Earth gravity after 186 days in orbit, Major Peake admitted that the first three days were "fairly uncomfortable" because of vertigo.
He added: "Once that disappears it's really a case of the body learning to balance again. That's what takes the longest, because your body has shut down the vestibular system for the six months in space. That actually takes a long time, to learn the finesse of balance."
Major Peake said he still had a "bit of work to do in the gym" but had experienced no physical problems.
However, he added that it would take six months to a year for the "microstructure" in his bones to recover.
"Overall I've lost 2% of bone density, which is remarkable - to spend six months in space and just come back with that loss," said Major Peake.
"That's really a testament to how far we've come in understanding how to live and work in space.
"This is really paving the way to those moon and Mars missions..."