Nadal's 130 plus MPH serve

[gzhpcu]

Phil,
my understanding is that the following laws do NOT hold
during a collision/contact of a racket with a ball:

1.a momentum of a racket is NOT preserved
i.e a momentum of a ball is NOT equal
2.a linear momentum is NOT preserved

3.a angular momentum is NOT preserved

4.an energy is NOT preserved



Please let me know whether Plagenhoef makes any comments on this subject

Plagenhoef does not cover this (in his book "The fundamentals of tennis").

However, in the other book i mentioned:

Momentum is ALWAYS conserved in every racket-ball collision; energy is always conserved, but it often changes form. Kinetic energy is usually not conserved.

Kinetic energy is not conserved because in real life some energy is lost - heat, or bending of the racket (for example) - which does not contribute to ball acceleration.

Momentum=mass x velocity; energy = 1/2 x mass x v^^2

[uspta990770809]

Firm wrist at impact

I assume he means a firm grip at impact and not during the service movement, which would be very negative.

It's exactly at that point that your wrist has to be relaxed to survive the change in direction in the racket. The server is throwing the racket up and building maximum centrifugal force right at and through impact and yet he has to apply sufficient centripetal force to keep the racket from flying away (I hope I have those two right.) The arm is outstretched and there is no where for the racket to go except to snap forward and this happens very fast. Even faster when you assist it with internal rotation/pronation. If your wrist is tight at contact, the muscles will work like a brake. One of the old tricks teaching pros have used for a very long time is to try serving holding on to the racket with just two fingers. Most beginner and intermediate players will actually hit the ball faster when they first try this. Sometimes it can help turn on a lightbulb for a more advanced player, but I don't really want them to be letting the racket move around that freely in their hand. Then they aren't really in control.

One of the things I had to learn the hard way was that you don't get anywhere by swinging harder when you are serving well. You've just hit 3 or 4 great serves and you really want this point and so you try to hit it a little "harder". Invariably, it goes slower if it goes anywhere near the target at all. When you are serving well, you have to just load and release, letting everything work. If you want more speed, release a little more. It's more obvious in a ground stroke where we just release through the ball with less topspin, but to a certain degree, the same is true for serving big.

don

[gzhpcu]

I tend to agree with you Don, seems like Plagenhoef had it wrong...

[gzhpcu]

In respect to grip firmness, I found these two references:

1) http://www.ncbi.nlm.nih.gov/pubmed/530030

The effects of grip firmness on the ball velocity after impact has been investigated in tennis. The average horizontal velocity of the ball prior to contact and after completion of contact was determined by a motion-picture camera. A tennis ball was fired from a machine to impact with a tennis racket, which was fixed in several different positions. No significant difference was found between the velocity of the ball after impact with a racket which was horizontally clamped and with a racket in a balanced, upright position.

2)"Teaching Modern Tennis" Brett Hobden and Gord Runtz

http://docs.google.com/viewer?a=v&q=cache:k8TehH5fN-8J:www.moderntennis.com/main/library/PTR-4.pdf+tennis+grip+firmness&hl=en&gl=ch&pid=bl&srcid=ADGEESi-Y0nR0j5B99smRFMmZzc6PTArqXZ18kcxOD-Bl6u_wBgOscOnpTFrT51-MCEA_zDL1-HDxdGUJvhdBziXuMHu5yJbtFhwL96Xn_bewqgefm1N2SwTRVZ1fGZKO02VTWimTg33&sig=AHIEtbS9G7OmiiDQHKB71PT1nu9Ez_r4eA

In the traditional game, most players hold their racquets far too tightly. You can test this by asking your players where their grips lie on a 1-5 scale. Tell them that 1 is the firmness with which they'd hold a small child's hand, just enough to control the racquet with one hand. At the other end of the spectrum, you can describe 5 as the firmest handshake they can muster. We sometimes call 5 the death grip. You'll probably find that most traditional players use a grip firmness of about 4, and some will report being off the scale. These numbers are far too
high for any type of tennis, be it traditional or modern.

Excessive grip firmness over tightens the muscles of the forearm, thereby greatly limiting the mobility around the wrist and elbow joints - mobility that is crucial to modern shot making. Holding the racquet too tightly can also lead to chronic arm injuries, including tennis elbow.
This happens for two reasons: (1) excessive shock to the arm on off-center hits, and (2)
excessive arm stress from the abrupt, truncated finishes we usually see when players hold their racquets too tightly. (We'll discuss finishes in more detail later under Follow Through.)

What is the optimal grip firmness? On the above 1-5 scale, it should generally be somewhere between 1 and 2 in both the traditional and modern games. The general rule is that the greater the racquet speed required, the looser the grip should be. In the ready position, grip firmness can be as low as 0 (zero), as here the racquet is fully supported by the "helper" hand. A relaxed grip allows arm and hand segments to move freely throughout the stroke, something that is especially critical in modern groundstroke technique. Without this mobility, players will be very limited in the amount of racquet speed they can generate through impact. This limits the amount of ball pace and spin they can produce and, hence, the range
of shots they can hit.

[gzhpcu]

And an old paper by Bruce Eliott....
http://journals.lww.com/acsm-msse/Ab...ness_on.7.aspx

The largest rebound coefficients, and therefore the rebounds with the highest velocity, occurred at the center of the strings with a tight grip. Decreases in rebound coefficients and increases in reaction impulses were recorded for off-center impacts when compared to the central impacts. Significant increases in rebound coefficients were recorded for an increase in grip pressure for off-center impacts.

This in contradiction to the previous article.

It seems to support Plagenhoef: a loose grip results in higher racket speed (this is consistent with Plagenhoef) but a firm grip results in higher rebound speed.

However, the test configuration is artificial, it does not reflect the motion of a server. It is static, so its application IMHO is questionable.

A loose grip gives a more relaxed serve and faster racket head speed, which offsets the sole advantage at impact of a firm grip... (?)

[uspta146749877]

A quote from Nadal about serve

He/Nadal also said that the new serve speed is getting his arm tired from time to time. Hence the inconsistency.

[uspta990770809]

Firm grip/loose grip??

And an old paper by Bruce Eliott....
http://journals.lww.com/acsm-msse/Ab...ness_on.7.aspx


This in contradiction to the previous article.

It seems to support Plagenhoef: a loose grip results in higher racket speed (this is consistent with Plagenhoef) but a firm grip results in higher rebound speed.

However, the test configuration is artificial, it does not reflect the motion of a server. It is static, so its application IMHO is questionable.

A loose grip gives a more relaxed serve and faster racket head speed, which offsets the sole advantage at impact of a firm grip... (?)

Key point here is, as you say, that the racket is static. So it has no momentum to transfer to the ball, only the reaction force when the tight grip resists the hit. When I started the Tennis Academy in Grand Central Station NYC in 1971, we had hundreds of beginners starting every 8 weeks, group lessons with machines in Grand Central Station. I got literally dozens of $3 rackets made in Pakistan or India (not China then) and we would have them let go of the racket just before impact to see how the momentum of the racket would work for them. I'm afraid there was more of getting the serving motion by throwing the racket across the net. Oh for the old days. The physics of it is that you transfer momentum from the racket to the ball. If the grip is very tight the mass (m) in M = mv is pretty large, but the velocity is also pretty small, and all of your body weight does not get transferred to the momentum of the racket (but I could have sworn hitting with Wimbledon champ Dick Savitt that he was doing exactly that). When we swing the racket and generate momentum of the "racket head" towards the target, v is much larger, but the m is really the mass of just the racket or even the racket head as you could hit the ball letting go of the racket just before impact (on a groundstroke, for example) and not lose a lot of velocity (I am not recommending this, unless you have some $3 rackets to spare for an experiment, and let me tell you, even then, it gets expensive! Of course, we were using wooden rackets in those days).

But on a different note, Phil, what a great library! Sounds like you have quite the collection of tennis books, especially on biomechanics, in your library. And you know where to find relevant texts from them. You aren't pulling this stuff from Google, are you?

don

[uspta990770809]

Note to Phil

I wasn't being facetious at all. I hit a couple of your weblinks and went to the sources. I didn't realize all these tennis books were so catelogued to be available on the web. I guess the key is Google. Perhaps you could get John to let you write a brief article on what the sources are you use to find these tennis texts on the web, etc. Somehow, I still bet you have a pretty good stash in your library at home!

don

[uspta146749877]

A spped of a racket vs spped of a ball

Some posts by SystemicAnomaly
in the thread

http://tt.tennis-warehouse.com/showthread.php?t=351971

could of some interest.The thread brings an old discussion:
is hitting a serve closer to a tip improves a speed of serve.
Does it relate somehow to a Don's favorite topic-pronation?
Sorry for mispelling speed in a title but I do nOT know how to fix it

[uspta990770809]

Follow the links

Some posts by SystemicAnomaly
in the thread

http://tt.tennis-warehouse.com/showthread.php?t=351971

could of some interest.The thread brings an old discussion:
is hitting a serve closer to a tip improves a speed of serve.
Does it relate somehow to a Don's favorite topic-pronation?
Sorry for mispelling speed in a title but I do nOT know how to fix it

I don't know about the post on the tip vs speed, but I hit the link and ended up finding some fabulous stuff on youtube that I hadn't seen before

This link

http://www.youtube.com/watch?v=pLf_MJXzBVg&feature=related

led me to a SOMAX breakdown of Roddick's serve that was really terrific.

That was the second place I went. First I went to a great APAS video from
Braden and Fitzell on Fitzell Tennis of Federer's forehand.

http://www.youtube.com/watch?v=pPLmCqGIotM

I think maybe we need to lobby John for an article on how to search for tennis articles and videos on the web (although it may be a little like Kris Kringle in Miracle on 34th Street telling all the customers where to go in the city to find what they were looking for even if it was a different store).

As for Julian's question about tip speed and pronation, pronation isn't going to effect tip speed relative to center of racket head speed much, but internal shoulder rotation and wrist flexion certainly will; and from what I've seen more than the loss in speed due to missing the sweet spot, as long as you are not all the way to the edge and still getting most of the benefit of the strings. When the Prince first came out in the late 70's (I tried it for a while in 77), it had a huge, but low sweet spot. Hardly anyone could serve big with it. It took me about a month to get the hang of serving with it and at the time it didn't seem like many people were figuring it out. It wasn't very comfortable, but you could serve big off the upper end of the frame. This was at a time when all kind of things were being tried. Fishback was introducing the "spaghetti" racket which was adopted by Nastase after he was beaten by it and soon outlawed. But the designers hadn't figured out how to make a big sweet spot further up on the face. Nevertheless, you could serve a lot faster if you could hit the ball on the upper end of the face. Current technology makes the sweet spot much higher and even the area above the sweet spot is much more forgiving than the original oversize rackets from the 70's. But as I hypothesized earlier in this thread (no proof), while pronation may play a minor role in supplying power prior to the hit, I think it may play a major role in as an enabling action which allows you to release the energy applied by shoulder internal rotation, elbow extension, etc without hurting yourself.

don

[uspta146749877]

Lobbying John

Don,
you should post something in a John's area.

[gzhpcu]

But on a different note, Phil, what a great library! Sounds like you have quite the collection of tennis books, especially on biomechanics, in your library. And you know where to find relevant texts from them. You aren't pulling this stuff from Google, are you?

don

Don, Here are some of the books I have at home:
"Fundamentals of Tennis" Stanley Plagenhoef

"Tennis" by Pancho Gonzalez

"How to Play Championship Tennis" Oscar Fraley (Mercer Beasley, Maureen Connolly, Ken Rosewall, Gardnar Mulloy, Lewis Hoad, Vic Seixas, Doris Hart, Tony Trabert, Louise Brough, Tony Trabert, Margaret Osborne du Prat)

"High Tech Tennis" Jack L. Groppel

"Stroke Production in the Game of Tennis" William Talbert

"World Class Technique" Paul Roetert, Jack Groppel - Editors

"Biomechanics of Advanced Tennis" edited by Bruce Elliott, Machar Reid, Miquel Crespo

"Biomechanical Principles of Tennis Technique" Duane Knudson

"The Physics and Technology of Tennis" Howard Brody, Rod Cross and Crawfored Lindsey

"Tennis 2000" Vic Braden

"Visual Tennis" John Yandell

"Bollitieri's Tennis Handbook"

"Mastering your Tennis Strokes" Larry Sheehan (Charlie Pasarell, Tom Okker, Arthur Ashe, Tony Roche, Harold Solomon)

For additional biomechanics info, I just Google for Brian Gordon and Bruce Elliott....

[gzhpcu]

In respect to hitting the serve up at the tip of the racket:

"Racquet technology can now produce a frame that will give maximum acceleration (ball speed) on the serve for impacts close to the tip..." Going on to say that the rackets have been made stiffer, and wider towards the tip...

page 199, "Physics and Technology of Tennis" 2002, mentioned in my previous post...

[gzhpcu]

Don,
The spaghetti strings were banned because Nastase beat Vilas with them....

That was the year he won both the French and United States Opens (Bjorn Borg beat him in the Wimbledon semifinals) and set a record of 50 consecutive match victories. It is a record, he pointed out, that would have been 100 consecutive victories if it had not been for Nastase and something both players recalled yesterday as "the spaghetti racquet," a double-strung affair with parallel planes of webbing that was banned almost as soon as it was introduced late in the 1977 season.

The fateful match was the final of a Grand Prix event in Aix-en-Provence in France, where Vilas, the only player using a conventional racquet, fought his way to a showdown with Nastase two days after tennis authorities announce that a ban on the "spaghetti racquet" would begin the day after the tournament. Vilas Walks Off

"They announced the ban on Friday and we played on Sunday," Vilas recalled, still smarting that Nastase had not abandoned the racquet in the face of the impending ban.

http://query.nytimes.com/gst/fullpag...gewanted=print