I mean if it is not some sort of general, the soldier is bound to become somewhat muscular due to the weight of the gear, especially if you want full body armor rather than the chest plate variant. But I agree there are other body types rather than bodybuilder/male model lean. the stuff weighs from 40-60 lbs. (depending if they use the tower shield or the chainmail plus leg protection).
Actually scratch that. If a general uses the armor he is BOUND to be able to fight in it (or at least ride a horse) they have to be somewhat fit.