Discussion in 'Tennis Tips/Instruction' started by gzhpcu, Mar 22, 2009.
When it occurs, yes.
There is a much more pronounced hitting up motion on the kick serves.
Wrist snap is the source of power and pronation is source of control. from James Blake
I call B.S.
Put up a link to the quote.
Here is what James Blake says:
Here is what Heath Waters from Virtual Tennis Academy says:
As I have said before, conscious wrist ulnar deviation and flexion works for me.
I live in Lugano, Switzerland and in June we host a very cozy ATP Challenger tournament at my tennis club. We have had players like Almagro participate. The players are very friendly and accessible. I will speak to some of them, and ask them their thoughts on "wrist snap", to get more insight on how tennis professionals view this question and then post the results.
I think what a lot of guys feel is the wrist snapping over and the centripetal force. I'm not sure they are actually flexing the wrist (overly contracting the forearm). I have a feeling more comes from internally rotating the upper arm. If I rotate my wrist using primarily my wrist, I can generate limited speed, but if I flick with my upper arm, it is much faster. I have a hunch that is what they do. Someone on here (supposedly with a 125 mph serve) a few years ago talked of snapping the elbow being the secret. Internal rotation is a key component of snapping the elbow. Just my take.
Have you ever worked with unlar deviation?
Found this here:http://www.revolutionarytennis.com/step12-5contact.html
I am not big on that site.
I don't want to say anything bad about anyone, so I will refrain from voicing my opinions in a public forum.
I don't agree with everything on that site, but it is the only I found that attempted to give an explanation which sounds reasonable for the Sampras serve followthrough...
hey guys, I have a quick q, on the kick serve when do you pronate?
Will says it all:
sureshs should watch that video 10000 times it would have saved pages of posts.
Pronation and tennis serve
Let’s analyze these pictures and try to figure out what is really vital for the powerful kick serve.
Figure 2.3 Set of the pictures around impact
What can I state about the body rotation? It looks like the body is frozen (because it is very slow) and hence, it cannot contribute anything significant to the racquet’s velocity. But the arm itself and its parts are rotating in the different planes with the visible angular speeds.
Definition: The Target Plane is the vertical plane, which includes the tennis ball during impact and the imaginary target inside of the deuce or ad tennis court.
The arm is rotating in the vertical plane by using mostly shoulder joint (also very slow joint). This vertical plane should be parallel to the Target Plane to provide appropriate direction of the ball’s velocity. The distance between these two vertical planes is defined by the racquet’s size and orientation at the point of contact.
There is also the wrist ulnar deviation (Figure 2.2),which directs the racquet upward, but this movement is not very important for the ball speed and I describe this motion later (see step 2.2).
On the picture 2.3.1 the vertical ray with arrow indicates starting point of the arm vertical rotation. All others pictures include this starting point ray and its own ray for measuring angular movement of the arm between starting point and current position of the arm (the angle ϴ). The numbers next to these rays show degree of the angle ϴ as result of the vertical arm rotation. On pictures from 2.3.3 to 2.3.7 the symbol ΩV represents angular speed of the arm for particular frame, ft is time elapsed between any two consecutive frames, ft=3.33 msec.
During this vertical rotation from Figure 2.3.1 to Figure 2.3.7 the arm travels 11° (Figure 2.3.7, ϴ=11°). The arm vertical rotation angular speed ΩV practically is constant on all pictures. It varies from 1.5°/ft to 2°/ft. The shoulder joint muscles do not produce any arm acceleration, it moves like a car coasts in neutral. Since, the arm is moving with constant speed the acceleration was achieved on previous steps of the serve, mostly, thanks to the fast elbow joint. The previous forearm movement forced the arm to move parallel to the Target Plane with angular speed approximately ΩV =2°/ft.
At the same time the arm pronation moves the racquet in the horizontal plane around 90°. Usually pros pronate something from 90° to 110°, depending on the previous supination. Suppose, the pronation provides 110° path of the racquet. It means the racket rotates in horizontal plane 10 times as many as the arm and racquet moves in vertical plane (ϴ=11°). The horizontal angular speed will be around ΩH=20°/ft, or 10 times as many as the vertical angular speed ΩV =2°/ft. Wow, this result is astonishing!!!
Question: Have legs, shoulders, and trunk motions contributed anything to the racquet horizontal rotation (pronation)?
Answer: These parts of the body produce a little bit to the arm and the racquet vertical rotation, but they are arguably even counterproductive for the horizontal rotation since the trunk rotates (clockwise), in opposite direction to the pronation (counterclockwise).
OK, it looks like I found the winner! The pronation can provide much bigger angular speed then others body limbs altogether.
Not so fast. In reality, we are interested in the linear velocity (the speed and direction) of the racquet, not just in angular speed.
Definition: The linear speed = radius × angular speed. The direction of this velocity is perpendicular to the radius of the rotation in the plane where the point of contact rotates.
The angular speed already discussed above. But, what is the radius? The figures 2.4.1 – 2.4.4 give an idea about calculation of these radiuses.
Figure 2.4 Federer serve Figure 2.5 Henin serve
Figure 2.6 ljubicic flat serve Figure 2.7 Stosur spin serve
Definition: Racquet efficient length Rel is the distance between player’s hand (point O on the Figures (2.4-2.7) and the ball during impact. I think Rel = 25” (63.5 cm) in the most occasions.
Definition: Arm efficient length Ael is the distance between shoulder joint and player’s hand. Since everybody have different arm size, I assume Ael = 25” (63.5 cm) as average length.
On the pictures above, RV is the radius of the arm and the racquet vertical rotation, RH – the radius of the racquet horizontal rotation (pronation).
RV = Ael + Rel × cosβ =25” × (1+ cosβ), where
β is the angle between long axis of the racquet and axis of the forearm (Figure 2.4-2.7). RH = Rel × sinβ=25” × sinβ
RV can vary from Ael to Ael + Rel (or from 25” to 50”) because cosβ has range from 0 to 1, depending on the β magnitude. RV can be never equal to zero, because Ael or the arm efficient length is constant and equal to 25”
RH can vary from 0 to Rel (or from 0” to 25”) because sinβ has range from 0 to 1. RH can be equal to zero and therefore linear speed would be zero! It can be very big problem for the tennis player. Maintaining the proper magnitude of the angle β before impact is absolutely crucial for pronation! On figures from 2.4.1 to 2.4.4 the best players keep β from 35° to 45°depending on the serve type.
Notation: |VLV| - Linear speed of the racquet in the vertical plane; |VLH| - Linear speed of the racquet in the horizontal plane. VLV and VLH are corresponding velocities. Reminder: the linear speed = radius × angular speed. In the last formula the angular speed should be expressed in radians. The angular speeds in degrees (from Figure 2.3) were: ΩV =2°/ft, ΩH=20°/ft. In radians they are ΩV = (π/90)/ft, ΩH = (π/9)/ft.
Then linear speeds in the vertical and horizontal planes can be calculated according to the following formulas:
|VLV|= RV × ΩV = 25” × (1+ cosβ) × (π/90)/ft = 25” × (1+ cosβ) × (π/90) × 300/sec
|VLH|= RH × ΩH = 25” × sinβ × (π/9)/ft = 25” × sinβ × (π/9) × 300/sec
The sum of the linear racquet speeds would be |VLV|+ |VLH|.
The results of the calculation are presented on the Figure 2.8
Figure 2.8. Linear speeds of the racquet in vertical |VLV|and horizontal |VLH| rotations and their summation
The data on Figure 2.8 demonstrate, if the angle β ≥ 12° the linear speed of the pronation begins to prevail on the linear speed of the vertical rotation.
OK, it appears, I found the proof! The pronation can really provide much bigger linear speed of the racquet than others body limbs altogether! But, if the angle β=0° the pronation produce nothing at all just the wrist perhaps can transfer some energy to the vertical rotation.
That’s why I repeat again, the best tennis players keep the angle β around 30° - 45° (Figure 2.4 -2.7). Maintaining the proper magnitude of the angle β before impact is absolutely crucial for pronation! If the angle β has the proper magnitude the pronation would be the most important and effective contributor to the powerful kick serves!
You must have established some kind of record for an initial post by someone on talk tennis with this analysis.
We'll look forward to other contributions in the future.
How about responding to the current recent thread started on "linear and angular momentum": http://tt.tennis-warehouse.com/showthread.php?t=347600
Do you think the following instructional videos demonstrate your point about the proper [β] angle between the long axis of the racquet and axis of the forearm?
Pat Dougherty - The Pro Grip http://www.vimeo.com/10566621
Racquet Angle on Serve from Jim McLennan of Tennisone.com http://www.youtube.com/watch?v=1t6bLABbebc&feature=related
Charliefederer, this is good idea. But, the problem is how we should maintain the proper value of the pronation angle β.
Ha ha! I see your point, toly... brilliant!
In order to apply topspin to a ball hitting down from 12 to 6 (instead of 6 to 12), you should hit the opposite side of the ball (I'm talking front vs. back, so this would be the side facing your opponent's court, instead of the side facing your racquet), which from a serve point of view, is pretty much impossible.
Anatoly Antipin firstname.lastname@example.org
1. The General Description of the Tennis Strokes
The tennis is the game about movement. There are a lot of a body activity, a racquet and a ball motion etc. It is the common practice to use Vectors to describe any object motion.
Definition: The vector is a straight line segment whose length is magnitude and whose orientation in space is direction.
Mostly, I will examine a velocity of the different objects.
Definition: The velocity is the vector. Its magnitude defined as the speed and orientation in space is the direction of the moving object.
All these vectors stuff maybe is not really very important, but can be helpful for understanding different tennis techniques. I’ll try to keep the matter as simple as possible.
The main distinction among the different tennis strokes
Definition: Flat stroke – the ball is not rotating after the stroke.
Definition: Slice stroke (topspin, sidespin, backspin, etc) - the ball is rotating after the stroke.
Question: How can tennis player produce the strokes according to their definitions?
Answer: If and only if the velocity of the racquet VR (Figure. 1.1) is the perpendicular to the string plane around impact spot, the stroke is flat. Or, in other words, if the racquet is moved in the direction of the perpendicular to the string plane around impact spot, the shot will be flat.
Figure 1.1. Racquet velocity (VR) in the case of the flat shot. Coordinate axis OZ and vector VR are perpendicular to the string plane
In all other cases, there would be the slice strokes. Since, it is practically impossible to maintain the velocity of the racquet perpendicular to the string plane, in reality, there are no pure flat strokes.
What happens if the velocity of the racquet VR (Figure. 1.2) has an arbitrary direction?
Accordingly to the linear algebra, every vector of the racquet velocity VR can be decomposed as a sum of two orthogonal (perpendicular to each other) components (vectors). The flat component VF is the perpendicular to the string plane and the slice component VS is the parallel to it.
Figure 1.2.The arbitrary vector of the racquet velocity (VR) along with its components (VF, VS). The string plane exists in the XOY plane
The flat component is mostly responsible for the boll velocity after impact VB (its direction and speed).
The slice component provides the ball rotation, but with some string interference can also change the velocity of the ball VB. It can happen due to the racquet strings could “bite” the ball or provide enough friction between the ball and strings and move the ball in direction of the slice component.
In case of the flat stroke, the slice component usually is equal to zero.
Something else about slice component
Since, the slice component VS is the vector, it can be also decomposed on two orthogonal components in the string plane. The vertical slice component VSV resides in plane perpendicular to the court’s ground. The horizontal slice component VSH belongs to the plane parallel to the court’s ground (Figure 1.3). Figure 1.3. Vector of the slice component along with its components
Relationship between defined vectors and common tennis slang
The upward vertical slice component VSV brushes the ball up, makes topspin, and also can drag the ball upward. The downward vertical slice component brushes the ball down, produces backspin, and pushes the ball down. The horizontal slice component VSH makes right/ left sidespin and moves the ball to the right/left.
In general, the boll spins in the direction of the slice component VS (brushing ball direction) and moves in direction of the flat component VF (perpendicular to the string plane).
Sometimes the slice component cannot produce any significant ball rotation but can change considerably the ball direction and speed. For instance, if the point of contact is the sweet spot and the flat component VF has very big speed. The ball just digs into string bed; the strings hug the ball very hard and do not allow creating any ball’s rotation during “digging” phase of the impact. Then strings catapult the ball very fast and the slice component does not have enough time to rotate the ball. However, while the ball is in digging and catapult phases the slice component still moves the racquet in its direction and as a result it varies the ball’s direction and speed.
That guy sounds right
That may depend on which part of you is leading, the wrist
or the forearm?
What the guy with the complicated vectors is saying seems to be this. We come up at the ball around 90 degrees, but when we get to the 90, we turn the forearm (if we are leading with the wrist first to hit), the forearm can't turn properly on the pronation, but if we are leading with the forearm first, then we will get the magnitude of angle on the pronation that we need because the forearm can only pronate more fully when the elbow is in front.
Sounds too complicated - I think I'll just lead with my chin...
lol that's a good one...
Yeah you need to snap the elbow, but i've never heard of snapping the chin
First is the forearm, second the wrist. What can I get from this?
Anatoly Antipin email@example.com
About angle β
βis the angle between long axis of the racquet and axis of the forearm. The pronation efficiency is sinβ, because the radius of the pronation (rotation) is RH =25” × sinβ. If β = 0 then RH = 0 and pronation linear speed of the racquet will be zero. Usually the zero produces nothing. That’s why , keeping β away from zero is very important for pronation.
When we swing the racquet upward our shoulder brings the upper arm in vertical and the forearm in horizontal position. After that, by using inertia and fast elbow joint, the forearm moves upward and angle beta usually equals 90 degrees. If we unbend the elbow completely, it brakes and inevitably the racquet starts moving upward by using very fast wrist ulnar deviation. This motion reduces angle beta and can kill pronation component of the racquet speed. But, we need this motion to create spin.
The main problem is how we should maintain the angle beta. I have some ideas, but I do not like them. Who can help?
Sorry for my Russian English.
When I examine at Sampras's Slow motion serve at 300 fps I can see before he starts the pronation that the shoulder leads.
I don't think the wrist should be the driver.
I want to discuss the problem with the angle beta.
There is no problem with pronation itself. Just rotate the arm counterclockwise as fast as possible. We also can use elbow snap, wrist snap and so on. That is it!
The problem is, for instance, if we trying to produce kick serve. We must use both, pronation to get power, ball speed etc. and the wrist ulnar deviation to create spin. This is dilemma; last action can kill pronation power completely. In this case pronation actually creates proper orientation of the racquet and nothing else. There is not anything to do with tremendous stress loads or whatever. Read my previous post carefully, please.
According to theory of the kinetic chain, we should start from slow joint and transfer angular energy to faster one. In case of the arm it will be: 1. the shoulder joint, 2. the elbow joint, 3. the pronation group of joints 4.the wrist. The wrist is last one, because it is the fastest joint of our body.
Can you give us the link to 300 fps video of the Sampras serve please?
Well I was only speaking of doing the 1st big serve. As I use Roddick's motion. Pronation helps with Spin and Control of the ball, it is a source of some power in the serve. But its not the major source. Good Knee bend and racket head speed are the other two I can think of. But to protect the wrist from stress it is better to use the forearm to pronate with if you want to serve hard.
According to my calculation, the pronation can generate angular speed aroundΩH=6000°/sec. Legs (knees bend, jump, or whatever), shoulders seesaw movement, trunk rotation, and fast elbow joint with forearm all together produce just ΩV =600°/sec. It is the myth good knees bend could be major source of the serve power, because they are very slow. We are talking here about speed around 100 mph. What speed can create knees? I am not MD and may say nothing about wrist, elbow, etc stress.
But, what can you say about the angle beta. Its magnitude is very important for any type of the serve (flat or spin, first or second).
By the way, the wrist cannot pronate at all.
I haven't yet seen a coaching lesson from Andy Roddick about
the racket head speed he gets, but the arms are not a force multiplier and that's why you get a limited racket head speed with swinging with the arms.... Bending the knees however gives you some speed.
The other pros on the men's tour serve nearly as big as Roddick too, But Roddick is more flexible...
Because the game is evolving and getting more powerful,
and players are getting more better trained, Soon we might see the men reach 160 mph with Roddick already leading the way with 155 mph along with Dent at 147 mph and others out of the 140-150 mph barrier and the woman soon breaking past 130 mph....
Actually some people do try to snap on the ball with only the wrist while others pronate
instead with the forearm or elbow.
Pronation is not versus “wrist snap”
The pronation always has to be used, at least, to provide the proper racquet string bed orientation. It should be perpendicular to the Target Plane. The best servers also use it to create pronation flat component of the racquet speed. There is no serve without pronation in professional tennis!
In case of the spin serve we must use the wrist ulnar deviation. To increase the flat component of the racquet speed we can also use the wrist flexion. The best servers utilize all of these motions.
Okay that's only about pronation.
Djokovick should be serving at 140-150 mph easily because he is capable of big serves like Dent, Isner, and Roddick and that's because he has got good external arm rotation like Roddick, but hes only serving at around 130 mph like Federer. Djokovick relies on his upper body strength to power his serve. Roddick takes full advantage of the speed force multiplier
Where is speed force multiplier in human being body? I cannot find it.
The greatest invention ever - the speed force multiplier!!!
As I remember from high school, there are two different mechanisms: 1. the force multiplier, 2. the speed multiplier. I Google the term “the speed force multiplier”. No such thing exists in their huge database. If you know something about this devise, you should immediately apply for Nobel’s Prize!!!
In our context, SIN(beta) can be treated as the speed multiplier. About the force multiplier, I hope you can tell us.
Its the hip where you get power in the serve.
So that's why steroid injections to hip are so popular with tennis players. ;-)
Sorry for bumping this thread, but I can't understand what's exactly this wrist snap? Is it the same as flexion?
For example in flick shots, Are we snapping our wrist?
I don't know if it's helpful to purposely manipulate the wrist. IMO, a full wrist release and pronation are the natural result of (1) a proper swing path, and (2) remaining tension free throught the stroke. Like a golf swing (which has more wrist release and pronation than a tennis serve), it seems to me that purposely manipulating the wrist and/or forearm would add a variable to the technique that would be too difficult to repeat with exactness on a consistent basis.
Just relax, focus on being tension free, and be aware of your swing path.
Sorry I'm not able to edit my posts yet, the first quote in my previous post is irrelevant.
Separate names with a comma.