Soon you will watch a video about an athlete whose improved performance has led some to suspect him of blood doping Think back to what you learned about the blood doping process. What do you remember about how blood
doping works and how it could affect cellular respiration?

Ais the answer hope this

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)