Well of course! My scaleysona Aaron started out as just a normal fur, but he later went into an intense bodybuilding phase in middle-school onwards right? Then something deep happened to him that forced him to quit... but after many many months afterwards he switched to MMA!
To that end, Aaron's a normal fur, turned muscle fur judging by his build, heh heh, and also Christian Fur and Fur Fighter (my selections: Normal, Muscle, Other).