1. an uncontrollable factor that might impact your normal workout routine and require modifications is a. tedium b. weather c. motivation d. time management

The answer would be D. Time management

Yoga i believe 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)