Originally Posted by boramiNYC
no, actually in your video your jump is just about the same height as sampras in above photos. if your knees hurt currently serving, you don't really have to jump. keep your left foot on the ground and just kick back with your right leg for balance. It might give you more consistency actually. and the loss of power is not that much actually. if you try this your stance should be turned even more left. see how your left foot is pointing when landing. closer to there for your left foot.
I'm not very tall though. But maybe i should give this a try on bad days.