So the camera distortion actually proves him wrong, not supports him.
Pronation versus "wrist snap"...
- Thread starter gzhpcu
- Start date
So the camera distortion actually proves him wrong, not supports him.
Actually, that is not the point. I am not saying that the racquet facing downward is what I am claiming. That proves my point ONLY for flat serves - those in which the face is on top of the ball looking in the direction the ball will go. In such cases, it is impossible for the head to point down and be moving up at the same time. But it is entirely possible and always happens for topspin serves. So unless the serve in the video was mostly a flat serve, my point is not proved.
My point was that the racquet head tip is moving down at impact. You don't see that, OK.
I watched the video again on my better home monitor. I will grant you the the 0:35 to 0:36 case. But that was "long" before the ball hit and when the commentary with the diagram begins.
Now look at 0:54 to 0:55 when the stroke is resumed again. Will you grant me that the frame was moving down just before it impacted the ball?
Actually I should have said that 0:35 was the point the upward motion was almost decelerated, at 0:36 it was complete and ready to descend, and from 0:54 to 0:55 it descended and then hit the ball. Do you agree?
I thought about it more, and I think both of us missed something. It might also be the clue to the argument in which some claim that a heavy frame swung slower produces the same ball speed as a lighter frame swung faster, and others believe from experience that the lighter frame with higher swing speed produces a faster ball.
It is not simply Mv (frame1) vs mV (frame2) (-- capital = bigger).
The momentum transferred to the ball is NOT Mv or mV from the frames. It is the DIFFERENCE in Mv or mV of the frame before impact and after impact - the frame continues to move after impact, though it is decelerating. A heavy frame transfers M(v1 -v2) and a lighter frame transfers m(V1 - V2). This amount divided by the mass of the ball is the ball speed. In which case is it higher?
In this particular discussion with one frame and one ball, it may be possible in theory for the ball to have a lower speed than the frame.
nousername
Rookie
to be honest, i'm not fully sure what you are trying to prove. some of what you say seems right, others do not.
here's my main contention with your comments: you say
"In such cases, it is impossible for the head to point down and be moving up at the same time."
you said that in reference to a "flat" serve. you need to separate the notions of ATTITUDE (i.e. the angle of the racket face) and VELOCITY (i.e. the speed and direction of the racket). It IS possible to be facing downward AND moving up. Use your hand as a racket face. Angle it downward, hold the angle fixed, then move your hand mostly left (or right) and slightly UPWARD. that is what a racket does (or should do) on a flat serve at contact.
do you agree that pro flat serves have topspin? if you agree, then the racket MUST be moving up at contact.
look at this link: http://www.coachesinfo.com/index.ph...e&catid=95:tennis-general-articles&Itemid=173
Sampras's flat serve has about 2700 RPMs of topspin. His "topspin/kick" serve had 4600 RPM. Other pros are the same, but just not as many RPMs.
THose are facts and actual measurements ... don't you see that PROVES even FLAT serves the racket is moving UP at contact???
casual analysis of a low-quality roddick video doesn't prove anything.
anyway, back to my lunch ... maybe i'll reply later tonight, if you follow up.
nousername
Rookie
maybe, but i think the quality is too low. BUT even if you are right, then it was a mis-hit by roddick, and most likely went well long.
If a flat serve hits down on the ball while moving up, that means it is hitting tangentially - the racquet would have shot up like a missile and caught the top of the ball as it is falling down, giving it a forward glancing blow. Roddick's motion would be to keep his racquet at 45 degrees up from the waist and thrust it upward like a sword. Then it would be moving up, facing down, and putting forward momentum on the ball. That is obviously not happening.
And maybe Sampras' flat serve is not a flat serve, but a topspin serve? If it has topspin, why call it a flat serve? Also, I think 2700 was for his first serve, not flat serve. And I see numerous WTA players who hit pretty flat serves without much spin. They are pros too. Not too mention the umpteen club players who hit down on the ball to produce a decent fast flat serve.
nousername
Rookie
just do my hand exercise. there is nothing like this "missle" thing.
Also, the point of the sampras stuff is that there is NO SUCH THING as a truly flat serve. ther 2600 RPM topspin serve is sampras's FLAT serve. "Flat" serve is a misnomer, and if you want to have a good serve you MUST understand and recognize that misnomer. FLAT serves are not flat!!!
Any ATP or WTA pro's "flat" serve has a LOT of topspin. period.
Take a look at this Serena serve:
http://www.metacafe.com/watch/1889351/serena_williams_serve_prostrokes_2_0_slow_motion/
From 0:11, advance frame by frame.
Initially you will see that she appears to be ready to hit "up" on the ball. She is aiming up, face is up, ball is higher. Then follow what happens - AS THE HEAD RISES, THE BALL FALLS. Just before impact, the racquet has stopped moving upwards, and the ball is hit on a slight descent (of course the face is pointing down/almost horizontal at impact).
She was reaching UP all the time, but the final hit is not up - it is horizontal tending to down. For a flat serve like this, if she was really hitting up, the ball would not land in.
http://www.metacafe.com/watch/1889351/serena_williams_serve_prostrokes_2_0_slow_motion/
From 0:11, advance frame by frame.
Initially you will see that she appears to be ready to hit "up" on the ball. She is aiming up, face is up, ball is higher. Then follow what happens - AS THE HEAD RISES, THE BALL FALLS. Just before impact, the racquet has stopped moving upwards, and the ball is hit on a slight descent (of course the face is pointing down/almost horizontal at impact).
She was reaching UP all the time, but the final hit is not up - it is horizontal tending to down. For a flat serve like this, if she was really hitting up, the ball would not land in.
gzhpcu
Professional
There is no such thing as a "flat" serve:
source: http://www.coachesinfo.com/index.php?option=com_content&view=article&id=350:tennis-highspeedserves-article&catid=95:tennis-general-articles&Itemid=173
this thread has been great dont try to prove your point and keep beating a dead horse. you can hit up and get a flat serve in because ALL SERVES HAVE SPIN. GET IT.
gzhpcu
Professional
Yup, even the serve of an old lady serving with a waiter's tray style, will have spin, even if it might be backspin...
stormholloway
Legend
You haven't made some great discovery. Of course all serves have spin. The ball always has spin. It's all relative. Flat serves do exist. It doesn't mean they have no spin
gzhpcu
Professional
Flat serves have less spin than other types of serves. The word "flat" is misleading. The trajectory of the "flat" serve is pretty much in the direction of the flight of ball, as opposed to spin serve trajectories which are more angled.
gzhpcu
Professional
Yandell, Elliot, Gordon discovered and proved it. However, apparently not all are aware of it.
nousername
Rookie
i don't think anyone is claiming "a great discovery".
but the truth is ... for anyone wanting to develop a good serve, there are a few "keys" that one must understand. for me, the primary piece of developing a good serve is the realization of the importance of hitting UP on the ball on ALL serves. the fact of the matter is at the pro level ALL serves (flat, kick, slice) all have some level of topspin.
suresh often fights this concept ...
but his comments are further confused by the fact that he argues contradictory points. on one hand he admits that: all pro serves, even "flat" ones, have topspin, which is correct, but then he tries to "prove" that pro flat serves are being "hit down", which would make topspin impossible. it's nonsensical.
so, in an absolute sense, no one has made any "great discoveries". but most recreational players, esp in the < 4.0 range, don't yet have perfect form, so they do NEED to make, or at least finally realizes, these issues if they want to develop there games properly ... in that sense, rec player do make "discoveries".
for me my epiphany moments were: 1) must serve with a continental grip (help facilitate natural un-forces pronation), as awkward as it is for a beginner, and 2) realizing i need to hit "up" even on my flat serve. i made both those change in a relatively short time frame, and it worked wonders on my serve.
(lastly, of course, some players are so good and natural they never even have to concern themselves with these concepts ... but for those of us less gifted, we do need to make a conscious effort to see, understand, and then implement these proper techniques.)
stormholloway
Legend
In my mind, recognizing that a 'flat serve' has spin on it isn't going to be a major influence on the development of the serve. I'm certainly no expert on the serve--it's been my Achilles' heel--but for me it's all about how pronation is timed in the chain. That's how spin is affected.
Overall, my problem is not tightening up at all during the motion. I seem to resist keeping my body loose, no matter what I keep telling myself.
Overall, my problem is not tightening up at all during the motion. I seem to resist keeping my body loose, no matter what I keep telling myself.
J011yroger
Talk Tennis Guru
My unsolicited $.02
You would be an entire level better player just by loosening up, calming down, relaxing, and just prioritizing a general smoothness in your game.
Of course that is so easy to say.
J
gzhpcu
Professional
You might consider the following:
Accelerating in or out of the back-scratch is exactly like accelerating from the top of the swing in golf. Both will result in a loss of precision and deceleration through the contact. This release and maximum speed is achieved by making the stroke more fluid and continuous in the back-scratch and then building both speed and tension in the arm by raising the shoulder and elbow up to the contact and at the same time holding them back, while dragging and lagging the racquet head. It also causes the muscles to tighten too soon. I find that just concentrating on accelerating the racket head just as you are about halfway up from the bottom of the racket drop, helps you keep looser. When I realized this, it helped my serve... might work for you as well...
J011yroger
Talk Tennis Guru
^^^ I don't ever, ever think of the racquet head, on the serve.
J
J
Kaptain Karl
Hall Of Fame
Me neither. I concentrate with all I'm worth on "catching the 3 wire," so to speak. I have my fourth-from-center Main make first contact and hope to be cleared of ball contact by the time the opposing 4th-from-center Main is passing.
Yeah. I'm lying. I'm kinda making fun of how some folks over-think this.
- KK
Yeah. I'm lying. I'm kinda making fun of how some folks over-think this.
- KK
J011yroger
Talk Tennis Guru
After the 3rd bounce I am done thinking.
J
J
stormholloway
Legend
All of my mistakes are tied to this idea in my opinion. It's 100% mental for me, because I know, in theory, what I should be doing. I'm just not doing it. I've been working on being loose as a goose out there lately.
For me, concentrating on accelerating the racquet head often leads to my pulling the racquet out of its loop prematurely in an attempt to 'muscle' the ball. I end up with a sore shoulder and little power. I try to force the shot instead of letting it happen. It's a work in progress.
Actually, all that is required for topspin is to hit off center towards the top of the ball while the racquet is moving in a forward direction relative to the back of the ball. So you can actually drive the ball into the ground and have it bounce before the net, all with topspin.
When I point to a video, you say it is of poor quality or the serve must have gone long.
When I say the face points down, a certain poster says it points up, and eventually it turns out his camera is not good enough and produces bending.
You say serves cannot have topspin unless hit up. It sounds true. However, serves can have sidespin which can be produced by hitting down or sideways.
A topspin and sidespin differ in the axis of rotation - the first rotates about an axis parallel to the ground, the other about an axis peppendicular to it. A ball spun around a certain axis can have its axis shift - even the earth's axis shifts. What is being measured in the studies - topspin, sidespin or spin around any axis?
A topspin serve is hit up 6 to 12 in the purest sense. Has it occured to you that this is equivalent to hitting down from 12 to 6? A ball hit down at 2 o'clock around the 2 - 8 axis will have spin around that axis - which can be decomposed into a topspin component around the 6 - 12 axis. It is like a twist serve hit up at 8 o'clock along 8 - 2. So, yes a component of topspin can be introduced by hitting down on the ball.
You know that the earth rotates about its axis say left to right looking at it in front. When it first started out, was the blow delivered on the rightside of the equator pointing forward, or the leftside of the equator pointing towards you? Can you tell now what happened? In the same way, a topspin component produced by hitting up and one produced by hitting down are indistinguishable.
And that is all just theoretical - do you know whether the serves I proved were being hit down had topspin or not? Pros hit with topspin is a general statement. Pros also double fault. General statements are not what I was talking about.
Thank you, thank you, thank you. See my last post
Once more, thank you. Topspin can be produced by hitting down.
Thank you, thank you, thank you.
gzhpcu
Professional
Do you know the difference between backspin and topspin? Same axis of rotation, rotation is however in the opposite direction. Hit from 12 to 6 and you get backspin.
JediMindTrick
Hall of Fame
I think that most club players hit the flat serve the way sureshs says, they hit down on the ball and hit an underspin serve that stays low after the bounce.
nousername
Rookie
sureshs, you have to slow down. 6 to 12 is the same as 12 - 6???? that is called complete opposite spin. 6 to 12 is TOPSPIN, 12 - 6 is called BACKSPIN.
kevo was correct that upward velocity is not necessary for topspin, but in tennis topspin is primarily generated by upward racket velocity. maybe i read kevo's comments wrong, but they certainly didn't sound like support of your view.
the part in RED says nothing about generating topspin while hitting down. you've got some major misconceptions floating around.
nousername
Rookie
i get the 1st sentence, and would never argue against it.
but your 2nd sentence is confusing ... in that i'm not sure what point your are making. i understand a serve can be hit into the ground before the net with topspin ... what does that prove?
nousername
Rookie
may i ask specifically what is your achilles service heel? spraying balls? going long? into the net? no power?
for me, pronation wasn't the issue. once i started gripping the racket correctly pronation just happened. i understand this is not true for everyone ... but the wrong grip does make it much harder and problematic.
here's why i think "hitting up" is key:
1) higher serve %: if you are not doing it, nor thinking of it, you are more likely to be thinking of hitting down which will impart backspin making your serves float long
2) more action: topspin makes serves jump. so if you can even get your "flat" serve to have lots of action, then take it!! it will only making returning your serve more difficult.
3) control: in addition to #1, topspin also adds control. more spin makes the and tennis ball more predictable. balls with little spin act like knucklehalls in baseball: erratic and unpredictable flight paths. topspin will make your control and placement more consistent.
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nousername
Rookie
when we talk about up we are not saying 100% velocity is up. we are saying like 95% forward and 5% upward. is that hard to believe on a "flat serve"?
for a pro kick i would guess numbers more like 70% forward 30% upward.
here's what i would have said:
we are just saying the racket is moving "slightly" upward during contact.
stormholloway
Legend
The result isn't necessarily the problem, as strange as that sounds. I know the serve isn't right because it doesn't feel right. I'm muscling the ball a bit. The weird thing is that some time last year, I completely figured it out and was really hitting bombs, and consistently. It just became automatic, for the first time ever. Unfortunately I had to stop playing for a while because I was moving. Then I came back to the game and the serve was gone. I'm just not letting the racquet do the work, and now it's gotten into my head.
I think I'm overthinking it.
J011yroger
Talk Tennis Guru
If you can put up a video I could help tell you what is going on.
A lot of times what you think is happening isn't what is really happening.
If you don't want to post up your video and get ridiculed by the TW masses, you can privately e-mail me the link, and I will respond via e-mail.
J
You are not getting it - I am not talking about rotation from 12 - 6 - that is back spin.
I am talking about the rotation AXIS being 3 - 9 and the ball spinning the same way as hit to 6 to 12, because it was hit 12 to 6 in the same direction, only on the top, not on the bottom. Read my earth rotation example again.
And as I said, this is not common in tennis - what is more common is the ball hit down at 2, which has a component of topspin in the 6 - 12 direction.
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Good point - in those cases where the racquet is moving slightly up, the phrase "hitting up" is probably unjustified. It is more like the ball was hit just before the racquet started moving down.
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I will be exiting this thread due to work commitments. I have successfully established that:
Pros sometimes hit down on the ball at impact - their racquet face is pointing down and the racquet head is moving down at impact.
It is possible to produce topspin by hitting down on the ball on the "other" side of where you would hit up.
Thanks for the interesting inputs.
Pros sometimes hit down on the ball at impact - their racquet face is pointing down and the racquet head is moving down at impact.
It is possible to produce topspin by hitting down on the ball on the "other" side of where you would hit up.
Thanks for the interesting inputs.
gzhpcu
Professional
Your statement makes no sense whatsoever:
You say the rotation axis is 3 - 9. This is the axis of the equator of the tennis ball. This is pure slice. Has absolutely nothing to do with topspin or backspin.
Hitting 12 to 6 means you are hitting downward north of the equator of the ball. This is backspin. Hitting 6 to 12 means you are hitting upward south of the equator of the ball: this is topspin.
SystemicAnomaly
Bionic Poster
^ No, a 3-9 rotation axis would apply to pure topspin not pure sidespin.
Not trying to "prove" anything with the second sentence, just though that some people might want to try it for themselves just to see that you can do it.
I like to occasionally encourage people to serve into the net or into the ground before the net so they get a better feel for hitting the ball down into the court. Most people in my experience are more likely to hit long once they start trying to serve hard, so that exercise helps them get a feel for serving down into the box.
nousername
Rookie
sweet!! you kind of agree with me!!! we are making progress!! nice.
the truth is that IS all we are talking about when we mention "hitting up"! that's it! that tiny little brief upward motion of the racket at contact. it's important b/c it has a big effect.
all serves the primary direction and velocity is almost completely forward. but since that is the common, given, standard part of the serve we don't always address it. instead the part of the racket motion that separates the serves (flat, kick, slice) are vertical and sideways component of motion. they are MUCH smaller than the forward component, but they are was really change the serve.
to finally, just to repeat: hitting UP is simply in reference to the small component of upward motion that the racket makes during contact!
(later, sorry guys, i'll try to keep the "hittin up" discussion in the "hitting up" thread later.)
gzhpcu
Professional
Yes, I see. It is all a question of definition. I mistankenly interpreted 3-9 as defining a horizontal plane, the equator of the ball, the middle point of which is the rotational axis. What was meant was a line through 3-9.
When it occurs, yes.
There is a much more pronounced hitting up motion on the kick serves.
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