[ HOW RUDE. Zack slows to a stop, standing up straight again and crossing his arms over his chest resolutely. (And trying not to laugh, too, because that's totally going to ruin his stern drill instructor air - which doesn't actually exist anywhere outside his own mind, but that's also beside the point.) ]

Hey, who's the ranking officer, here? [ Okay technically not him, either, but. Old habits. ] You'd better believe it when I say warming up is important, no matter how funny you think it looks. If you don't give your muscles a little forewarning, you could strain something really badly, even in practice.

[ And that last part, at least, he does mean sincerely. Launching into another stretch, he moves slowly and demonstratively, this time. ]

Come on, go like this! You'll start to feel the difference right away. [ Don't make him turn this into a proper lecture!! ]