is it illegal to be pumping your racket before you hit the birdie? my coach told me to stop doing it. if it is not illegal, what is the side effect of doing it?
In videos of doubles matches, I've often seen people do this when receiving serve, but not at other times. I don't know the reason.
I know what you are referring to - it's a kind of jitter along the plane of the racket face. I often do a few "shakes" when I'm prepping my serve or my partner is (but not when I'm receiving) - I could only describe it as a nervous tic, like the way some snooker/pool players' fingers bounce up and down when they're on the shot (Mark Williams is a good example). My racket hand just wants to swing, I guess. As to its legality, I can only find rules pertaining to the server's and receiver's feet, not their hands, so I can't see it being an offence, especially if you stop when the server addresses the shuttle.
apparently my coach said it may cause a mis-hit because the position of the racket may not be correct. does it really make that much of a difference?
Another reason when receiving is to get the movement momentum for a quick thumb grip return shoot. Other than that, your coach is correct, its useless. I would think also it should be ilegal to pump the racket when serving, as the rule stated that a serve is a single movement.
you already kinda answered your own question. it is not illegal, but your coach thinks it is causing mishits.
I think it really comes down to how much you move your hand... I have seen some players move so much it looks like a double motion which is illegal.
i do see some of the malaysian players do that when they're about to smash or a backcourt drop shot, or he danish players do it when they're about to receive a flick serve. i guess if you're quick enough, then your racket could recover from the pumping quick enough to receive the serve, but if you're not quick enough, you might misplace your racket out of position to receive the serve, which causes you to mishit?