The fitt principle stands for

a. frequency, intensity, time, and type
b. fitness, intensity, toughness, and type
c. frequency, ideal, time, and toughness
d. frequency, ideal, time, and type

when you rub, you also apply pressure, that pressure can urge the poop to come out. i think that when your rubbing, you also might be slightly breaking it up and that can further fill the stomach.  

out of the choices i'd say d the ability to set goals, mainly because to desire to continue you need motivation but it isn't motivation in that part, but setting goals means you have an endgame and you want to reach it which sums up motivation.