A family friend of the race car driver claims the star is 'sending signals from his distant world' as he is cared for in their home in Geneva, Switzerland.
Schumacher suffered a head injury while skiing in the French Alps in December 2013 and has since been unable to walk or speak.
The anonymous source was quoted in German magazine Brunte as saying Schumacher's toned physique is helping him do 'well in the circumstances.'
'Corinna and the children [Mick, 18 and Gina, 20] hope to this day that a medical miracle happens.'
The seven-time world champion was put into a medically induced coma for six months after the incident in the French Alps.
Doctors operated to remove blood clots from his brain, but some were left because they were too deeply embedded.
Medics described his condition as 'extremely serious' after his admission to Grenoble Hospital, where he underwent two life-saving operations.
Schumacher, who remains immobile and cannot speak, is understood to have a 15-strong team of medics looking after him at his home in Geneva, Switzerland.
In December 2016, a statement from his manager, Sabine Kehm, said: 'Michael's health is not a public issue, and so we will continue to make no comment in that regard.
'We have to protect his intimate sphere. Legally seen and in the longer term, every statement related to his health would diminish the extent of his intimate sphere.'
The statement continued: 'Michael has always been very protective of his privacy, even during the most successful times of his career.'