Absolutely. I always wondered who the people who did that thought they were impressing. Do, however, be loud with the noise you're supposed to be making and keep yourself off the ground as much as possible. When I got worn out pushing I'd just go down a little but yell as loud as I could, and I never got singled out for it. I didn't do that until I legitimately couldn't keep doing full pushups (or whatever extracurriculars we were practicing) though, and that's key. The people who consistently failed to put out were the ones who brought the most misery on themselves and their class. Don't be that guy.
There's nothing quite like a bathroom full of guys who can't sing trying to sing a song they don't know with vocal cords already stretched to the breaking point. One of the candios who indoc'd us had us sing Roxanne all the time. I never liked the song, but now I laugh a little whenever I hear it.
