I have that ask what make the body move​

When you decide to move, the motor cortex sends an electrical signal through the spinal cord and peripheral nerves to the muscles

Ibelieve this would be an obstacle.

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)