Like most typical sports coaches, Sternback wears a white T-shirt and shorts with white threadings that somewhat appear to be ripped and a hat (much of the attire is which lime-green). Much of the attire has the letter "M" (the insignia of Mellowbrook) patched on, like most coaches this is to show support that represents the team and school school and like all coaches he carries a whistle. Much like his namesake, Sternback is physically stern and very muscular (as shown when he rips off his shirt) though this masculine physique is hidden beneath his shirt; his namesake also maybe more in reference to his personality.
Stern is like his namesake very stern to the point and is very observant to the extent to read a future athlete's true potential. He seems to be very persuasive and takes pride into himself and his work (this is noted when he tells Kick he has trained some of the best athletes). His persuasions show no bounds it would seem showing him to very persistant in the matter (as do most characters in the show) this goes far enough to excuse Kick out of gym class in order to train him in which he states "I'll get you out of gym class" which seems to be his trump card to train most of his students his way.
He trained many people to be good athletes, although one of his students became a peanut vendor.
He, along with Ms. Dominic, are gym teachers in the show.
However despite this he has only appeared once throughout the show
Though he looks somewhat unfit his physical appearance shows him to be muscularly built, however his detailed physique is hidden under his shirt and is only revealed when he removes it. This is experienced in the same fashion with The Simpsons characters, Ned Flanders and Groundskeeper Willie, with both character's true appearances hidden under their attire.