Why do so many quarterbacks lift their foot of the ground just before the snap?
I don’t remember them doing it when I watched football as a kid and now it seems almost all of them do it.
I believe it’s a cue to the center, who is usually looking through his legs at the QB.
It’s used from the shotgun formation to cue the center, especially when the crowd noise prevents verbal communication. Many times, you’ll see the QB lift his foot 2 or 3 times, so the defense doesn’t know which signal is the real one.
Earlier in the signal count (i.e., before the ball is snapped), the QB may lift his foot as a signal to the player who’s going to go in motion, to start doing so.
Now that that’s answered, a different QB question if I may:
Why do QB’s, especially young ones (but plenty of veterans do this as well), pat the ball right before they throw?
Just a WAG: is he making sure his throwing hand has the grip that he wants?
Some of those pats may be fakes to freeze a LB/DB in place momentarily and free up a receiver elsewhere on the field.
Namath used to do that all the time. (I know that doesn’t answer your question, but there you have it.)
I have sometimes noticed myself doing this - completely unconsciously - when playing catch out in the yard.
I have no idea why, and if I concentrate I can not do it. Since my level of football playing does not extend beyond the occasional pitch-and-catch session, I have no reason to really address it, but I think I could teach myself to stop for good if I tried.
I think I’ve heard that at the NFL level, a quick release is very important and little extraneous gestures like that slow it down just a hair - so QB’s seeking to improve their level of play make the effort to eliminate it. If they’re at all like me (and, true, if they’re playing in the NFL they’re rather different from me 
), it’s an unconscious action that is at best neutral and possibly slightly harmful.
I see something similar in baseball. an infielder will pick up a ground ball and if he has an easy play to first, he’ll take a step or two and before the throw, taps the ball against his glove hand or into the pocket.
Great username-OP combination.
He’s looking for receivers to throw to. His hands separate, he looks at the receiver, decides not to throw, and puts his hands back on the ball. Then he moves to the next receiver. He’s also pump faking to receivers. Done quickly, this all looks like he’s patting the ball.
Unless you’re talking about something else. At what point in the throwing motion are you seeing a ‘pat’?
the pat in question is with the off-hand and it’s just a weird human quirk. a TERRIBLE habit that QB coaches at even the HS level try to eliminate.
the RB/WR equivalent is taking a gather step before taking off. if you’re lined up and ready to go downfield, your feet are staggered like they’re on blocks and you’re ready to bolt downfield. then whe the ball is hiked, you pick up your back foot and put it back down to push off. YOU’RE ALREADY POISED TO RUN! JUST RUN!
i had to run many a lap to cure myself of that habit.
Thanks. 