Duke closed his eyes in pleasure. You'd think skin stretching would hurt but no. His muscle pushed on that skin as their size doubled in a matter of minutes. Even his cock grew almost twice its' size. The bench below him started to creak. You make your way out from the back room to feast your eyes on the growing beast before you. His eyes still closed, trapped in a sea of ecstacy. His biceps soon the size of his head, legs thicker than a tree trunk. You watch and wait to see how long he lasts. Hopefully, longer and bigger than the last.