Pronation versus "wrist snap"...

[gzhpcu]

Everyone is talking about pronation, but what is its real role to contributing to racket speed, as opposed to being a natural result of a good swing?

Most articles discard "wrist snap", even though many pro players say they do it.

Let's share thoughts on this.

First, read this article: http://www.revolutionarytennis.com/d...p_evidence.pdf

The article quotes Brian Gordon's book Serve and Science. Brian Gordon is one of the few to really have done systematical, biomechanical analyses of the tennis serve.

Interesting is his finding that:
1) pronation contributes only to 5% of total speed overall in the kinetic chain
2) wrist action contributes a whooping 24% of total speed

Moreover, he states that

"And indeed, wrist flexion is a major contributor to racquet speed
near and at contact. The significant portion of this flexion is caused
by active and conscious muscular contraction and associated joint
torque."

or in other words, that players do indeed consciously "snap" their wrist when serving.

The wrist snap sequence being defined as consisting of wrist extension, ulnar deviation, flexion.

Some quotes from Stanley Plagenhoef's classic Fundamentals of Tennis:

Any change in racket head position after impact is due to joint adjustments to retain a position of non-stress. The turn of the racket face outward is the result of the anatomical structure of the shoulder.

In addition, if the hand is flexed, a natural rotation of the hand due to the bone structure of the wrist turns the palm outward when the arm is overhead.

The amount of racket head change varies with the individual, and the amount of racket head recovery from this outward turn varies with the length of the follow-through. A long follow-through to the left of the body is characteristic fo the slice serve, whereas a short movement down to the right is characteristic of the twist serve. The more abrupt the stop, the more muscle is being used. The overall result is that the body is continually attempting to maintain a rhythmic, smooth motion and at the same time exert optimal muscular strength while eliminating unwanted stresses. Therefore, arm rotation does not aid in hitting the ball harder but is simply the natural result of a good swing.

(my emphasis)

[gzhpcu]

Have an old book written by Pancho Gonzalez. He said he did a "wrist snap"...


Yes, I know they did not speak of pronation in those days... but if he mentions wrist snap, it means he was doing it consciously...

[gzhpcu]

Watch this video from Jim McClellan (tennisone):

http://www.youtube.com/watch?v=7bsYF...eature=related

Notice that the added leverage (=power), in the angled racket approach he recommends has more wrist action...

[gzhpcu]

Some more thoughts:

When coming up out of the bottom of the racket drop, towards the end of the trajectory, prior to ball impact:

• forearm rotation turns the racket from on edge on to facing the ball for proper contact
• the abrupt acceleration, causes the wrist to extend backwards
• the wrist (and racket), if under a loose action only, will only start coming forward when the arm starts to brake (to transfer kinetic energy to the wrist)

So the question is: can we augment this extension-flexion wrist action by consciously willing a wrist snap?


Old-timers evidently thought so. From another old book of mine Stroke Production in the Game of Tennis by William Talbert:

Arthur Ashe has just struck the ball at the 10 to 11 o'clock position by snapping his wrist, whipping his racket up and over the ball...

[theZig]

DISCLAIMER;
I do not mean to belittle or insult anyone in anything I ever say. Should you find this proceeding example unnesessary, that is fine. I post this in hopes that SOMEONE reading this thread will benefit! Thank you.


Get a soda can, a paper, a pencil, and some string. Wrap the paper around the can (Any cylinder will do, really) and draw a line with the pencil straight up and down the can (Line A). Now, draw a line starting from the same point going up again, but as you go up TURN the can (Line B) and be sure that your pencil is going straight up as the can turns. Get a string and measure the two lines. Line B will be longer.

Assume that both lines are drawn at the same speed in terms of going "up" the can. The only difference between the two, then, would be that one line is drawn straight up while the other is drawn as the can turns. Line A would reference a straight up swing, while Line B would represent pronation. Now, lets work with the formula Acceleration = Distance traveled/Time taken. As said before, the time taken for both lines to be drawn was the same, however Line B was longer than Line A; therefore Line B has more acceleration. We will now refer to the "lines" as "swingpaths".

Now, let us apply this to the formula Force = Mass x Acceleration to the tennis serve. Mass will be the same for both serves A and B (since your arm and racket do not magically adjust) , however as stated before the acceleration is higher on swingpath B and therefore Serve B will inheirently have more force.


Things to consider
As you have already stated, pronation itself is a result of a good swing. In otherwords, simply swinging up with your racket (Line A) is NOT a good swing! I oftentimes find that people who consciously attempt to pronate through their serves also tend to "arm" their balls. I feel this is a result of people not understanding how large a role their bodies really do play. While the swing is obviously important, I feel that proper rotation of the shoulders/hips, drive of the legs, and a number of other things to be equally important. For example, if one were unable to rotate his shoulders, he would not be able to swing properly! Understanding what the arm itself does is fine, but it is also important to understand the rest of the body.


About your thoughts on the wrist snap:
This is a tough one, in my opinion. I personally am in the camp that you do not need to purposely think about snapping the wrist. I feel that if the toss is in the correct position, and the correct swing is used, the "wrist snap" should happen naturally.

I understand your point where should your forearm continue at a constant speed, your wrist would be "dragged" behind the forearm itself slows down, allowing the wrist which is moving at a higher speed to "snap out", much like a pendulum motion. However, given the fact that our arms are not perfectly straight , I prefer to think of it more of a whip. The same principle applies to a whip (The tip will not "snap" out until the handle goes in another direction), however this only applies if we are talking in one direction. For example, whips are often "waved" (I don't know the proper term) in two opposite directions (but on the same plane). A simple way to show this would be to take a string and go up and down, and watch the tip.

The serve, however, has several different directions going on. In a previous thread, you discussed the racket drop and how it effects the serve. As the racket begins to drop, however, our bodies are begining to rotate and push up with our legs. This gets our swing going, however our arm does not need to slow down right before contact because the "handle" of our serve is not our shoulder, but our torso. As the body is being propelled up, and our shoulders rotating, that would be the "initial" action (Much akin to say, lifting up a string). The reason why we do not have to decelerate our arm is because our body stops moving once our shoulders have opened up and our feet off the ground, we hit a point where our bodies are no longer accelerating and we are coming down into the court. That action would be the "second" action (quickly bringing the string down). The whip involved here is the up-down motion of bodies. The core muscles act more like bending a plastic ruler, and then letting it go. The result is the majority of the energy used to pull the ruler back propels it forward as well. The shoulder rotation adds another dimension.


Conclusions

I feel that pronation is, as you said, a result of a good swing, but that you do not need to consciously think about snapping your wrist. My basis for this is that pronation is the most efficient way of increasing acceleration, and that same efficient swing also lends hand to a natural wrist snap, like the end of a whip.

I would love to discuss this further with you and the other members of the board. Again, I do not mean to insult anyone or try and "prove them wrong". I am not here to "be the bigger man", but to discuss and learn more about tennis.

[larry10s]

^^^^^ great post. nice to have another analytical thinker in the discussion. yandell in an article "myth of the wrist- serve" if i can paraphrase correctly(john if you read this correct me) the foward motion or flexion if the wrist seen is not from a concious muscular contraction of snapping the wrist but the result of the combination of the left to right swingpath and pronation. after those 2 occur and contact is made the wrist will naturally go foward as the hand and arm relaxes after contact

[larry10s]

another quote from brian gordon One could anecdotally argue that much of the wrist joint motion measured during the approach to contact during the serve is passively accomplished through motion-dependent torque. This joint motion, combined with that actively caused by muscular activity early in the upward swing, leads to impressive joint rotation speed leading into contact. So impressive, that any last ditched effort to increase it at contact by consciously "snapping the wrist" would likely be fruitless.

[gzhpcu]

Originally Posted by theZig

I would love to discuss this further with you and the other members of the board. Again, I do not mean to insult anyone or try and "prove them wrong". I am not here to "be the bigger man", but to discuss and learn more about tennis.

I am baffled at why you think you think you need to make a disclaimer to post your opinion, but then, you probably have more experience posting in this forum than I do, since I only started to get active recently.


You make very good points and certainly would appreciate discussing with you or anyone else to learn more about tennis. I have been posting quite a bit on the serve not to influence persons to my way of thinking, but to get a kind of peer review and see if some of my ideas have any merit.

I have been experimenting myself with consciously trying to flex my wrist at contact, and have the feeling that it really helps.

[gzhpcu]

Originally Posted by larry10s

yandell in an article "myth of the wrist- serve" if i can paraphrase correctly(john if you read this correct me) the foward motion or flexion if the wrist seen is not from a concious muscular contraction of snapping the wrist but the result of the combination of the left to right swingpath and pronation. after those 2 occur and contact is made the wrist will naturally go foward as the hand and arm relaxes after contact

This is certainly correct. I just have the feeling that the flexing of the wrist can be increased if at impact point, if you consciously try to whip it across the ball.

Try it out, see how it feels, and let me know.

P.S. I remember someone having asked Ivanisevic a question on how he managed to have such a great serve and he replied: "I just toss the ball up and hit it"... or something to that effect... Sampras also was told his coach not to make him think about his serve. For those of us let talented, thinking might help us improve...

[fuzz nation]

I can appreciate the inclination for a disclaimer, since some issues around here are sort of gospel for some of our pals. I've been shaking my head at the pronation issue for a while and I share the opinion that it is a result of things done correctly in a service motion - definitely not something to actively try and perform.

I also don't see wrist snap as something that's accomplished by employing the muscles in the wrist in a service motion. I think that the wrist should be looser in a good serve than with pretty much any other shot. Once the racquet is accelerated upward toward the ball in a service motion, it's the arm/shoulder's action of stopping that forward motion at the grip end of the racquet that makes the racquet head snap past it - with a loose wrist effectively acting as a hinge. It might feel like those little forearm muscles are trying to help to "whup" the racquet head through the hitting zone, but I believe that good racquet motion in a healthy serve is generated with a passive wrist.

[gzhpcu]

From an International Tennis Federation presentation on the biomechanics of the serve regarding the forward swing:

contributions to racket speed at impact
• Leg drive 10%
• Trunk flexion 20%
• Internal rotation 30-40%
• Hand flexion 30%

• Wrist action following internal rotation is wrist
flexion
• Shoulders are almost parallel

Ball impact location
• Ball travels forward and left related to left toe
• It is not hit on the right but on the left side of the body

Up and out hitting action
• Feel like the right shoulder is hitting out
• This is affected by the leg drive
• This movement can be helped by using a
“cue word” such as: “up and out”, “drive”

Spins
• Slice comes by putting the shoulders parallel
to the net
• With the shoulder over shoulder movement
the player can produce more topspin
• Flat serves do not exist

Other aspects
• Yandell (199 found that there is not such thing as a
flat serve in professional tennis
• The hitting action is up and out
• In the serve you don’t hit through the ball
• Landing foot:
– 95% Left - left
– 5% Left - right

You can see the whole presentation here: http://www.itftennis.com/shared/medi...6_original.PDF

[gzhpcu]

Originally Posted by fuzz nation

I also don't see wrist snap as something that's accomplished by employing the muscles in the wrist in a service motion. I think that the wrist should be looser in a good serve than with pretty much any other shot. Once the racquet is accelerated upward toward the ball in a service motion, it's the arm/shoulder's action of stopping that forward motion at the grip end of the racquet that makes the racquet head snap past it - with a loose wrist effectively acting as a hinge. It might feel like those little forearm muscles are trying to help to "whup" the racquet head through the hitting zone, but I believe that good racquet motion in a healthy serve is generated with a passive wrist.

You might be right, but Brian Gordon thinks otherwise, as in the quote in my first post. I just know that it seems to work for me, but I might be fooling myself into thinking that...

Lets do an experiment: without the racket raise your arm in a prior to impact postion. Now do two things:

• first accelerate rapidly forwards (with pronation coming naturally) and a loose wrist, then
• do the same, except, additionally try to consciously flex forward at impact

Do you feel any difference? I seem to get a more pronounced whipping action and outward facing palm of my hand when i consciously flex at impact.

[Kobble]

Originally Posted by gzhpcu

You might be right, but Brian Gordon thinks otherwise, as in the quote in my first post. I just know that it seems to work for me, but I might be fooling myself into thinking that...

Lets do an experiment: without the racket raise your arm in a prior to impact postion. Now do two things:

• first accelerate rapidly forwards (with pronation coming naturally) and a loose wrist, then
• do the same, except, additionally try to consciously flex forward at impact

Do you feel any difference? I seem to get a more pronounced whipping action and outward facing palm of my hand when i consciously flex at impact.

That's because you have no momentum being transferred. The motion has to come from somewhere. If you can flex you hand at 100 mph, but the object is traveling at 110 mph, I don't think you can add anything to it.

[BorisBeckerFan]

What cleared it up for me was when I was around 12 and my coach said I wasn't attcking the ball with the edge of my racquet enough. If the butt of your racquet is pointing up during the racquet drop and you are swinging up at the ball with the edge of the racquet following through forwards and outwards with racquet face still leaning somewhat down the pronation and wrist snap should happen naturally. Your arm will due the pronating right before impact. I know some players conciously add wrist snap but I guess there's good examples of players who do and don't do this. When I'm really trying to get some extra juice from my serve I add some wrist snap.

[junbumkim]

Originally Posted by BorisBeckerFan

What cleared it up for me was when I was around 12 and my coach said I wasn't attcking the ball with the edge of my racquet enough. If the butt of your racquet is pointing up during the racquet drop and you are swinging up at the ball with the edge of the racquet following through forwards and outwards with racquet face still leaning somewhat down the pronation and wrist snap should happen naturally. Your arm will due the pronating right before impact. I know some players conciously add wrist snap but I guess there's good examples of players who do and don't do this. When I'm really trying to get some extra juice from my serve I add some wrist snap.

I absolutely agree.

If you drag the butt cap of your racket from the back-scratch poistion (when the buttcap is pointing toward the sky) toward the ball, then the tip of the racket is going to snap upward, the racket meets the ball, and the tip of the racket will sort of snap downward.

This really is the entire process of pronation and wrist snap. Your formarm has turned outward (pronation), and your wrist has snaped.

The aforementioned process is probably what you want to concentrate when you want to increase your racket head speed in serve.

[BorisBeckerFan]

One thing that I would like to add is if anything is not clear for whatever reason or you're watching a youtube video on the serve or whatever and it doesn't quite click, I really recommend getting a good instructor to help. I am not a teacher but have had the benefit of lesseons since I was young. There are many good tennis instructors around the world that can help all of this make sense. Even if you don't get regular lessons the serve is the most important shot in tennis and it's really worth it to have the basic mechanics of the serve locked down.

[gzhpcu]

This article in Revolutionary Tennis maintains that the wrist snap is a conscious effort:
http://www.revolutionarytennis.com/w..._evidence.html

Here a couple of relevant quotes:

Is wrist movement a conscious thing, known as a muscle-driven joint torque, or is it involuntary, known as a motion-dependent torque because other body parts are moving? Pundits only claim the one, but Brian Gordon found both: He also found wrist movements to be conscious. What pros call a wrist snap is causative, active, purposeful.

Throughout his expanded analysis Brian Gordon points out that while people studying this "don't as yet fully understand the origins of all the joint forces," and that "every player will use his own combination of muscular contraction (joint torque) and joint forces (motion dependent torque) to rotate the segments of the hitting arm," he nevertheless states there is active, conscious movement of the wrist by muscular contraction.

There are indeed more strikes to be called against those shouting "myth" because it is intellectually dishonest and professionally irresponsible to claim an either/or, black/white scenario of what dominates kinetic contribution at a joint: only a muscle driven joint torque or only a motion depended torque? That is, if a motion dependent effect is dominant it should not be interpreted as a lack of conscious contraction, and vice versa, because both will be present, both will contribute (as the author indicated to me). Furthermore, there is a lot of crosstalk going on between relaxation and contraction and of allowing motion dependent effects to occur, issues that science now admits it knows little of but of which athletes are aware and amateur analysts can not imagine.

Perhaps the rub is that our tennis pundits view only contraction as "the" conscious muscle effort whereas athletes and true Biomechanics scientists also know relaxation to be conscious effort. Being able to relax the hand and wrist allows one to train the arm to perform its myriad operations in a serve, allows the racket to be placed optimally during the swing path, and ultimately sets the stage for the wrist to jump through its hoops when required. If you tense up the wrist this can not happen.

The next tennis can the scientists are kicking is whether a pro actuates the wrist movements or whether the wrist bends forward because the arm is pronating. In other words is the wrist active or passive. They claim the wrist "is along for the ride," pros say otherwise.

[BorisBeckerFan]

I am not stating that this "is the case" but simply offer this as a possibility.
These two concepts of snapping the wrist conciously and the wrist snapping as a result of proper technique are not mutually exclusive. Maybe they could both be happening at the same time. When I snap my wrist there is no detraction form the momentum proper technique and has placed on the wrist. One of the keys here is fluidity.

[gzhpcu]

Originally Posted by BorisBeckerFan

I am not stating that this "is the case" but simply offer this as a possibility.
These two concepts of snapping the wrist conciously and the wrist snapping as a result of proper technique are not mutually exclusive. Maybe they could both be happening at the same time. When I snap my wrist there is no detraction form the momentum proper technique and has placed on the wrist. One of the keys here is fluidity.

That is also what the revolutionary tennis article says. I tend to think both can happen at the same time. If the wrist is loose, it will snap, I just have the feeling that by additionally consciously willing it, the wrist snap gets accentuated more.

[BorisBeckerFan]

Originally Posted by gzhpcu

That is also what the revolutionary tennis article says. I tend to think both can happen at the same time. If the wrist is loose, it will snap, I just have the feeling that by additionally consciously willing it, the wrist snap gets accentuated more.

Thank you for posting the article, I'm going to go read it right now.