Menstruation is triggered by a drop in the level(s) of

Menstruation is triggered by a drop in the levels of progesterone. It is a hormone in the body that functions to regulate and stimulate a number of functions especially in females. It is a sex hormone and has an important role in pregnancy.

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)