I've noticed foil and saber fencers at our club, when they practice lunges, they tend to throw their weapon arm out, and allow it to collapse back when the front foot hits the ground. It looks like you're throwing a hand-shake a some someone then pulling it back like a prankster.
In epee, you don't see the same thing. Epee fencers at the club seems to keep a stiff weapon arm in the lunge, and while they may relax their shoulders, they don't have the habit of retracking their arms.
Am I seeing things? Is there some practical/theoritcial reason for this?