In the following diagram, each circle represents a body system. The brown section in the center shows functions of all three systems, the overlapping areas around the center show functions of the two overlapping systems, and the individual areas of red, blue, and yellow show functions of each unique system.

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)

Ansinterlock;