Also
That's from the Mk VI armor's wiki page under Armor Components. While I do stand corrected in saying that it was actually the Mark VI, I did say I wasn't sure which model utilized it first. Armor Lock is a built in feature, the one in Reach was just a gameplay gimmick. It's also why you could lock your armor in cutscenes without technically having the armor lock attachment, because in cannon it's built in and always available.Lock-Down System: The Mark VI also introduced a "lock-down" system, which protects muscles and joints from traumatic, high-impact injuries by seizing the suit into a rigid posture.
And you can't say you weren't talking to me this time, since you clearly are responding to me. :p