I'm starting to play tennis again after a 20 year break. Most of my ground strokes are coming back reasonably well, though my serve seems to be very inconsistent (I used to have a pretty decent one way back when, but not any more). Trying to job my memory, I watched the series on fuzzyyellowballs.com on the serve. I was quite surprised about a few things. Firstly I was taught that your racket was lowest in its swing at the same time that your knees were most bent - it seems this is not the case according to the series where your racket is still swinging down as you are coming up, but starts to recoil into the shot as you take off. When did this change or was I a wayward tennis teenager? Also, when you watch the footwork, some people do the knee bend, then move their back foot forward, just behind the front foot before the jump - why? What's the difference between this and keeping both foot in pretty much the same place? Finally, when did the arm pro-nation come about?