Well badminton is a forward swing with a good amount of wrist rotation at the peak. Racquet ends up about waist level but you have to remember that the racquet is about 86g (or a hair about 3oz) so... yeah if I try to swing a tennis racquet at the speed I swing badminton I will de-socket my shoulder
So I will practice swinging upward and finish with elbow high. If I'm swinging up how do you impart forward velocity?
This is Fu Haifeng. #1 ranked world doubles doing a smash. If you turn up the volume a little you can hear how WICKED that sounds. He is teaching how he hits it (in chinese thou). There is a slow motion capture in this clip.