knee bend and jumping

[andyroddick's mojo]

are we supposed to jump after our knee bend in a normal groundstroke?
I know pros like roddick jump high, while other pros seem to be lifted off the ground slightly. My coach tells me I have to bend my knees more, then my other coach tell sme that I'm landing off balanced, so I was wondering, how important the knees and jumping are for groundstrokes. I hit with topspin, loopy forehand, remember...these are just like normal groundstroke rallyballs. Should I jump up?

[Livefreediefree1]

well if your knees are bent you have less area to cover and you can easyilly get to the ball but its really what your more confortable with iprefer to jump because it gives that much mor speed