Open Stance

[Bungalow Bill]

BTW, I found a book called The Physics and Technology of Tennis written by three physicists who have dedicated much of their professional life studying the physics of tennis. Crawford Lindsey, Howard Brody and Rod Cross do an excellent job describing almost every aspect of the physics of tennis in this large, comprehensive and detailed book. I have only read a small portion of this book but from what I can tell (its pretty technical) the M in Newton’s famous formula F=MA is only the tennis racquet as John Yandell said. So a person’s body weight makes no difference. Another physicist, who did a study on baseball hitting, told me that you could throw the bat at the ball and it would have the same effect as swinging it. So this could be applied to tennis as well.

Interesting where did you get the book?

[tennismaverick]

Sorry I didn't get back to you earlier but I haven't looked at this site for a few weeks. I sell DVDs on ebay and one of my distributors (the largest in the US for books, DVDs and CDs) had it. If you want a copy I can sell you one at a discount. This book is probably the best source on the physics of tennis.

[johnyandell]

Have you seen Technical Tennis? More user friendly by the same main author Rod Cross.

[tennismaverick]

I have not read Technical Tennis but was debating whether to buy that book or the one I ended up buying. The one I bought is very long and technical and will probably take me years to read the whole thing. Maybe the other book would have been better.

[johnyandell]

More relevant and easier for sure...

[tennismaverick]

Someone challenged my newly founded assertion that the racquet is the only mass that matters because they said, "Try this experiment. Balance your raquet on the ground on it's side and toss a ball at it. Racquet falls down, right? Now hold the raquet in your hand and do the same w/o moving your raquet hand. The ball bounces backwards with more force, right? You definitely didn't add any accelleration."

I assumed they were correct, since this seems intuitively logical and so I never performed their experiment. Finally, I decided to try the experiment just as they described. The ball rebounded the exact same amount regardless if I held the racquet or rested it on the floor. I also had a friend hold the racquet in his hand as tight as he could but not move the racquet as I threw the ball at it. I then had him dangle the racquet by two fingers just holding on with the lightest amount of pressure as possible. I then threw the ball at it. Again, there was no detectable difference in how far the ball rebounded. In both cases, where the racquet was not held or held lightly, the racquet fell down or moved backwards yet the ball rebounded the same amount as when the racquet was being held. Like many things in physics, they are not intuitive and can only be proven experimentally. This was one of those things. Fascinating to the physics challenged among us.

[johnyandell]

Wow, that's pretty interesting--I mean the racket is connected to the hand and arm and that must mean something...one of the mysteries we can continue to investgiate, but I am still pretty sure that stepping into a shot isn't a directly transfer of "weight" into the ball!

[tennismaverick]

I was very surprised by the results and even though I have done that experiment 10 times now, I still have a hard time accepting the results. But try it yourself and let me know if you get a different result. It is not intuitive but it is consistent with what one physicist told me about baseball hitting. That you could throw the bat at the ball and it would have the same effect as swinging the bat. So clearly, just the racquet head speed and weight of the racquet make a difference.

But stepping into the ball and holding onto the racquet increases racquet head speed for most people. Try stepping away from the ball when you hit it and you won't hit it nearly as hard. I think at the 4.5 level and lower its obvious that stepping into the ball helps most of the time because people don't hit the ball that hard in the first place. But at the pro level, they hit it so hard that if they just get their racquet on it, the ball will rebound with great force.

So if they are moving backwards when they hit it, they will still be able to hit it hard. I also think that they have figured out a way to swing the racquet fast by not stepping into the ball and at times even stepping backwards. I think they do this to favor hitting the ball in the correct contact zone and will sacrifice power to do that in favor of the improved consistency. But again, if they are hitting a slow ball it appears that they step into it or transfer their weight forward when hitting it. I still think transferring your weight forward helps most people and is a good practice for lower level players.

Certainly transferring your weight backwards or even leaning backwards would not be recommended. I don't know about just being balanced and neutral though. I know if I step into the ball I can accelerate my racquet more but does that cause me more unforced errors? I don't know and I guess I will have to experiment with this. Also, what will be best for me might not be what is best for the pros since no one I play comes close to hitting it as hard as the pros. I would like to see Agassi or Federer play a 3.5 player and see if their hitting style changes any. That would be interesting.

[johnyandell]

I think the swing is the whole thing. I don't think it's the stance so much per se as that lower level players have a better chance of turning and swinging thru the ball if they step.

As for Federer versus a 3.5: That's not a possible comparison. There would be no points because the 3.5 would neverreturn one Federer ball because of the speed--if he did it would be a fluke rebound shot. There are probably 200 levels between 3.5 and world class.

But what you do see is the top players step in based on ball height. When it's low or they take it on the rise they do step in.

[mntlblok]

The Physics and Technology of Tennis

Just finished the book over the holidays. Sort of fun to read if you don't make yourself try to delve too deeply into the formulas (formulae?). I have a list of the pages with errors on them if anyone is interested. :-)

I was hoping to find more on biomechanics than what was in the book (very little). The most interesting thing to me was the tendency of a tennis ball to slide, bite, or bounce depending on the court surface and the angle of the ball's flight to the court. It turns out that the ball and strings have that same relationship with "bite", etc. Practically speaking, I doubt that the knowledge gained from that would be of much practical value. I think you just need to deal with a lot of different balls a lot of times to develop a feel for what it's going to do off the court or your strings (or lines on a clay court).

The other thing I found fascinating was how much evidence there is that the type, gauge, tension, and age of the strings in the racquet makes *very* little difference.

I've now seen many times on this site how much the ball slows down both on it's flight through the air molecules and especially from the friction of hitting the court.

Since taking John's advice and videotaping my groundstrokes (since getting my new video camera) I have much less interest in biomechanics. :-) He was right, of course.

I'm now much more interested in learning how to use mental pictures (especially with my eyes closed) to make the necessary changes in my technique. At least I now have the number of changes that need making down to a (possibly) reasonable and doable number. :-)

Setting the shutter speed at 1/4000 takes care of nearly all the blur. I've now even learned about firewire and movie-making software. How can somebody sell you a firewire cable and not ask if you have that connection on your computer?? Fortunately my wife is a geek. :-)

What do you mean "I ramble"? :-)

Kevin
Savannah

[johnyandell]

Yeah I gave up on the big book--trying again with Technical Tennis. Rod is a friend of mine. The thing about the strings is interesting but goes against every player's experience. 2lbs is a big difference in the way any racket plays--guess it could be an illusion, but I doubt it. And just ask any tour player about big banger string.

As for being right, well sometimes.

[mntlblok]

Yeah I gave up on the big book--trying again with Technical Tennis. Rod is a friend of mine. The thing about the strings is interesting but goes against every player's experience. 2lbs is a big difference in the way any racket plays--guess it could be an illusion, but I doubt it. And just ask any tour player about big banger string.

I now can't find the spot in the book, but what I found most interesting was a test of about 40 players (at a tournament in the far east somewhere?) If I remember correctly (big if, I'm learning) a significant percentage of them couldn't tell a *15lb* difference in tension. Hope I have that right. I don't know their level of play. I'm no pro, but after a few minutes of play with any racket, I'm playing pretty much the same as with any other.

Interestingly, a local tennis shop put on a "wood racket tournament" for the local 4.5 league last year. After about the first round, you really couldn't notice any significant difference in play among the players - at least, *I* couldn't. The feel of the grip is about the only thing that tends to aggravate *me* if it doesn't feel right. Of course, I also drive a minivan. :-)

Kevin

[johnyandell]

Yeah that's the thing that seems very odd to me. Every been around a tour player who is unhappy with a string job from a new stringer? Remember Warrn Bosworth--there was a reason he made a living making racket identical. I doubt a player is gonna take one out of the bag in a match and not notice 15lbs. Actually he is gonna fire his stringer.

[tcoach]

Open stance/Neutral stance

To me the difference in OS and NS is when to use it. There is no doubt in my mind that when trying to pinpoint a shot such as hitting a target(example: orange cone) my students hit it more times with the NS. So I teach that in general the OS is used for mid-point ralleys and then when the opportunity arises to end the point or at least to set up the end of the point a NS should be used.

[johnyandell]

The limiting factor is ball height. If the ball is too low or too high it will dictate stance--some balls in the middle you can make a choice.