Toly, you are right, I didn't read everything, have a lot of work. But without reading, I think you must be wrong somewhere. First at all, mathematics behind physics of human body is very complicated and you use very simple methods. They may be good alone, but the result - that pronation generates power at serves - doesn't agree with my experience and knowledge. I'll try to find the weakness of your analysis in a few days, k?
Bhupaes, yes, I know, knowledge hurts
I play tennis since late 70., with a 10 years break in 90. (those women...). All my life, I was a very good server. 2-3 aces per game? Where is a problem? 10+ aces per set? Quite normal. 200 kph? Rare, but doable.
Unfortunately, my serves were unstable. There were days when I made one mistake after another. Also, I had big problems with my back and elbow. I'm not too young (44 now), so I decided to change my sequence. The goal was to make it more stable and more friendly for my body.
Three or four years ago I began to think about new sequence. I knew that the days of powerful serves were finished, I had too many things to change - I made some movies and my serves were technically horrible. So I read many scientific papers, spent many hours thinking about physics of the stroke, played a lot at the wall, watched many pros. I decided to introduce one element after another. Now, my new sequence is almost finished. It's not perfect, I know, but it's technically quite solid. So, it took me three years to do this:
There are minor things to improve, but fundamentals are quite solid now and I can think about increasing power. I hope I'll do this in a few months.
What's important here is that what you see on the movie is a result of my UNDERSTANDING of tennis physics and biomechanics. No trainers. No mindless copies of pros' movements. Yes, I spent many hours watching Federer, but I am like a cat, I have to find my own way. It was really funny to find an amazing biomechanical part of sequence and... discover it in Federer's sequence. So, if my serves or forehands look a bit similar to Federer's - it's because we both use the same physics. He was not a source of technique for me, he was a method of verification.
I'm really proud of my sequence now. Not because it is so good, but because it shows the real power of understanding. My sequence is a product of logical thinking, not a result of mindless rules like "do that", "don't do that", "pronation generates", "jump at serves" etc.
Originally Posted by bhupaes
The other thing is the significance of the high elbow. I found that I could not get my elbow high unless my body was tilted.
Do not think about elbow. "High elbow" is a mindless rule. Trainers use it because they do not understand physics and biomechanics. Now you know that the forearm rotates along axis made by upper arm and shoulders. Just remember that this axis should be straight - and tilt it (high elbow is a result of this action - just a result!). This is a very simple thing to do. One hour at the wall and it will be quite natural (but it will take you months or years to remove "quite"...
). You will also see that your elbow moves forward - exactly as in another popular mindless rule. Everything seems to be more simple - and more easy to do.
What's important, tilting gives you better point of view on the ball. That's a small bonus for our visual perception system.
Yes, you are right about the role of pronation and supination at modern topspin forehands and backhands. I have some scientific papers and they say that it generates 30-40% of kinetic energy of the stroke. It is quite easy to demonstrate (maybe one day I'll make a movie). Of course you have to remember that power of modern forehand topspin or backhand is also a result of energy transfer along kinetic chain (this is what people usually don't see and don't understand in Federer's strokes).
Now you can see the real power of understanding in tennis - in practice. We were talking about serves, but now you know what to do at topspin forehands and backhands. That's a kind of magic for me, that tennis is so intellectually beautiful. Its beauty is very similar to the internal beauty of special theory of relativity. I was so inspired by this coincidence that I created my own "special theory of tennis" (scientifically correct of course). I will present it one day, it's too good to be hidden.