When was stephen hawking diagnosed with motor neuron disease?

He was 21 years old when he was diagnosed and was not expected to make it past his 25th birthday. 

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)