Who is considered the father of motor behavior?

Franklin M. Henry
By the time of his obligatory retirement in June 1971 at the age of 67, Franklin M. Henry had spent more than 30 years as a faculty member at the University of California, Berkeley. His contributions to exercise physiology, aviation medicine, and especially motor behavior research had been extensive.

Inaccuracy is a disadvantage

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)