The junction between the digestive tract and the respiratory system is the trachea epiglottis esophagus pharynx

The junction between the digestive tract and the respiratory system is the pharynx. 

Drop out early hard to juggle both

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)