Well, the last rules I saw for this are now one edition old.
Player's Option: Combat & Tactics (Boo! Hiss!) had fatigue rules. Basically, everyone has a number of fatigue points equal to their hit points; fighting costs 1 fatigue point per round. Once fatigue = 0, you reset, are fatigued, and fighting now costs 2 points per round. Once fatigue equals 0 for the second time, you either pass out or cannot pursue combat.
I don't think there were armor-specific rules, or class-specific; it was expected that warriors would be able to fight longer than wizards.
Somehow, it doesn't have the flavor of the new edition
I don't really think they're necessary, because they're just more bookkeeping, and I don't play those sorts of games. But you could look up PO:C&T and look at the rules there.
As an aside, I remember that a lot of the maneuvers in 3E seemed new to people when introduced in 3E; but they were most of them in C&T, so I didn't see the novelty. Also, a lot of things in the 2ndEd High-Level Campaign book are now feats (there's something called All-Around Attack that's fairly familiar

).
TWK