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  • bottle
    replied
    ~

    Great, but what's the matter with the Don videos which are already up?

    Leave a comment:


  • llll
    replied
    Originally posted by tennis_chiro View Post
    Yeah, that is a lot to follow without a video. I'll try to get something up and give a link to it by the end of the week.

    don
    THANK YOU DON

    Leave a comment:


  • tennis_chiro
    replied
    A little much

    Originally posted by llll View Post
    im sorry but i get lost in your description
    could you post a youtube video???
    pretty please
    larry
    Yeah, that is a lot to follow without a video. I'll try to get something up and give a link to it by the end of the week.

    don

    Leave a comment:


  • llll
    replied
    Originally posted by tennis_chiro View Post
    Okay, Bottle, I went through the Cross article once more. Try this

    You can't create the actions Cross is talking about with specific deliberate actions. (I think.) However, you can perform drills that include intrinsically the motions and actions that must be included in the total service motion to accomplish the effects Cross is talking about in the article.

    You will not generate those 150 lb. forces deliberately, but if you generate enough racket head speed and simply hold on to the racket (!), you are by definition exerting the necessary centripetal force to balance the centrifugal force the momentum of the racket head has created. If your wrist is relaxed while controlling the racket head, the racket face will direct a force perpendicular to this centrifugal force which powers the ball forward.

    So there are a few steps to this drill.

    First, you have to understand what my "Figure 8 drill" is. I think you are familiar with this but other members of the forum might not be. Just pretend you are making continuous swings standing in an alleyway extending to the target and there are 30 foot high glass walls on this approximately 2 foot wide alley. Here's a clip of the figure 8 drill.

    http://www.youtube.com/watch?v=gaS-qtQWym4&NR=1

    Unfortunately, I didn't have audio (I thought I did) when I made this recording. I need to update it and put some more videos up, but haven't done it yet. You could use this in conjunction with the positions demonstrated by Kerry Mitchell in his first service article

    http://www.tennisplayer.net/members/..._serve_part_1/

    Now, we get to the specifics of generating your increased racket head speed.
    We start with internal rotation.
    Stand facing the net with your upper arm next to your body and your forearm perpendicular with the racket shaft actually parallel to the baseline, the palm up, racket face horizontal and off to the right of your body. (for righties. Are you a lefty, Bottle? I mean left handed.) You can even rest your right elbow in your left hand.
    Without taking the elbow out of your left hand, rotate your forearm to the left so the racket face moves 180 degrees to where it is face down, palm down, but the face again horizontal, but on the opposite side of your body.
    Swing it back to the start.
    Now go back and forth as quick as you can without moving your right elbow out of your left hand.
    Optionally, you can go one stage further with this particular step by swinging the racket so far to the left that the face goes past horizontal and the shaft even begins to point down as it goes more than 180 degrees. At this point, you would be adding a little pronation and your elbow would pull out of your left hand.
    In any case, do this back and forth as fast as you can. Feel the internal rotation and how the racket head goes past the wrist.

    Now you try to take this feeling into doing the aforementioned Figure 8's. Try to "whistle" the racket at its highest point in the swing, just at or after contact. Next try it actually hitting the ball.

    Want more?

    Stand with a slightly open stance at about 45 degrees to the baseline (because this is an abbreviated motion and you won't have the benefit of a full swing to turn the hips and shoulders forward from the normal starting position).

    Position yourself so the shoulders are actually parallel to the baseline (or even perpendicular to the intended path of the ball).
    First put the racket face up to the contact point. (Remember the racket is not straight up. For a righty, the forearm and the racket shaft form a 10 to 20 degree angle at contact. Just guessing on those numbers. Check with John and Brian's data.)
    From the contact point, while leaving the elbow exactly where it is pull the racket head back down as you externally rotate as you reverse the internal rotation that took the racket up to the ball.
    Now, while leaving the elbow where it is, swing the racket head up to the contact point and past to the "Sampras racket head down" point. Now swing the racket back and forth along this path. It's kind of like what we were doing in our first exercise here, but a little different.

    Note: it is important that at the starting point of this motion the butt of the racket is pointed like a flashlight at the ball and also in the direction of the target. Most people have to be corrected from a position where they have the shaft of the racket pointed too far to the right and they are unable to generate sufficient force in this swing in the direction of the target to get the ball over the net.

    Once you get a little feel for it, starting from that point with the elbow up in front of you, toss and "tap" the ball over the net. Range of motion and a "clean" contact is the goal here, not speed.

    When you feel you can do that a little bit, try to incorporate the feeling into the figure 8 drill. See if you can get a little more "whistle". But don't worry too much about speed in the actual hit just yet. "Hard" is your enemy right now. "Relaxed" is your friend.

    Now we go to the next step. Maintaining the same stance position you had in the last drill (about 45 degrees open), go to the "trophy" position. Now see if you can toss the ball (always transfer your weight forward as you toss the ball; you don't get to use your normal backswing, but you can still have a little rhythm with a rock or just a back to front shift as you toss the ball) and then do the last drill from "trophy" position and still finish with the right elbow up and the "Sampras racket head down" ending…literally. Of course, that means you can't swing too fast; but you can still propel the ball a little faster than we did in the initial version of this drill.

    Now if you can feel this, you can try and put that feeling into the Figure 8 and go for even more "whistle".

    Bottle, all this is pretty removed from what Rod Cross was pointing out. But one key to doing this drill is that the wrist must be in control, that it is it must have the racket handle snug in the hand and against the heel of the hand; at the same time, the wrist must be completely relaxed and just acting as a hinge to allow this full range of motion. Certainly, there will be some wrist flexion and ulnar deviation involved as you move the racket head up to the ball, but the true primary forces are going to be coming from other elements.

    And finally, if you can put all this together and feel a little more racket head speed and get the "whistle" to happen at the right time (up through impact and just beyond), you will be forced to exert significant centripetal forces to overcome the momentum and forces of the racket as it swings up to the ball; thereby you will have to do what Rod Cross is describing in his article. But I don't think you will be able to accomplish that if you try to "exert centripetal force on the handle of the racket with a vector at the heel of your hand counter to the vector exerted at the first knuckle and the fingers". Not going to happen!

    Good luck with it, Bottle. And Phil, you might try this too. And Ed, did you get this down?

    good night,
    don
    im sorry but i get lost in your description
    could you post a youtube video???
    pretty please
    larry

    Leave a comment:


  • julian1
    replied
    A paper for you

    Don,
    please check your E-mail
    Last edited by julian1; 06-13-2011, 05:16 PM.

    Leave a comment:


  • tennis_chiro
    replied
    Not as simple as it seems

    Originally posted by julian1 View Post
    I would suggest two analyze 2 pictures/graphs:
    Fig 3b
    Fig 10
    Don,
    please let me know what do you think about these pictures/graphs
    At first glance, it is pretty obvious: the arm comes to an almost complete stop as the racket head approaches impact. I say obvious for the serve because I can explain that the measurements are in the x/y plane and don't account for the internal rotation aspect of the swing at that moment. We know wrist flexion and ulnar deviation are not enough to account for the racket head speed at that moment, but they are contributors as well. But figure 10 is for the forehand and that is a kind of a "scratch my head" realization because there is not that much at the wrist at this point except some radial deviation to generate topspin...so that is a little more surprising.

    When I first started the Clark Graebner Tennis Academy in Grand Central Station 40 years ago (6/7/71!), I had the classes start with teaching grips and contact points on the first lessons (750 students in classes of 8 with 8 ball machines on two 55' courts); second lesson we focused on the follow through (no wraps back then). I don't think I knew how right I was to put the emphasis there. I've always felt it was really important to get the student to feel the contact point out in front of them at the appropriate spot. I think we've had discussions on this forum, led primarily by Geoff, about the importance of "defending the contact point". Rod Cross's article just points up even more how important that attitude is.

    I still have a little question in that while this measures angular velocity, the question is in what plain is that taking place. If it is in a plain parallel to the upward movement of the racket towards the ball, we could calculate by its' angle how much the arm is moving upward at contact (which I believe would not be zero). If it is measured in the horizontal plane, then there is no accounting for the upward movement of the arm and that is a little disingenuous, because the arm is really still moving pretty fast. It may be true from a physics point of view that the upward movement in the z plane should not contribute to linear velocity in the x and y planes, but let's let the data show that.

    don

    Leave a comment:


  • julian1
    replied
    Two pictures to analyze

    Originally posted by tennis_chiro View Post
    Thanks, Julian. That was really great. I've now done my mental gymnastics for the whole day, maybe even the whole week.

    Wow. Talk about paralysis by analysis. I'm not even going to consider linking to the American Jounal of Physics article. I probably need to read that a couple of times to really digest it, but there are a few things that this article validates on a more applicable level.

    (I like to think my students walk away from my lessons thinking, "Wow, that was interesting. Don really knows what he is talking about!". This is great information for me, but I already have a reputation for being too technical. If I integrate too much of this overtly into my lesson presentation, as true as I believe it must be, students may be really fascinated during my presentation, but as they don't get to "reread" that presentation, they will probably walk away saying, "What the hell was that about?!")

    So:
    1. Trying to hit your serve "harder" when you are serving really well will probably make the ball go slower, if not totally destroying your rhythm and effectiveness. Hit it "faster", not harder, by releasing more completely.

    2. On the groundstrokes, use the wrist as a "passive hinge" controlling the ball, but not snapping through it as you try to keep the strings on the ball as long as possible.

    3. In the same vein as the passive hinge, try to swing the racket head, not your arm or your hand. This means the wrist maintains its position and slight wrist cock as you swing forward to the ball on the forehand.

    4. On the other hand, this validates Phil's effort to emulate the Federer wrist extension/flexion flick at the beginning of his forehand forward swing.

    I do think we missed a whole lot of stuff here about internal rotation and the optimum angle of the racket shaft to the forearm to create effective power from internal rotation (you don't get much if the upper arm, forearm and racket shaft form a straight line...which they do in the frying-pan-grip-serve used by rank beginners). I wish we could get a comment from Rod about where that fits into the picture. Probably, I just need to do a little more reading in "The Physics and Technology of Tennis" (Is it in there, Julian?)

    Well, that's good for a start on Sunday morning. Curious to hear what the rest of you think.

    don
    I would suggest two analyze 2 pictures/graphs:
    Fig 3b
    Fig 10
    Don,
    please let me know what do you think about these pictures/graphs

    Leave a comment:


  • tennis_chiro
    replied
    Whole new meaning

    Originally posted by julian1 View Post
    http://twu.tennis-warehouse.com/lear...lependulum.php
    To be exact it is really a paper by someone else describing a recently published article in American Journal of Physics by Rod Cross
    It has Paragraph 8 devoted to forehand
    Thanks, Julian. That was really great. I've now done my mental gymnastics for the whole day, maybe even the whole week.

    Wow. Talk about paralysis by analysis. I'm not even going to consider linking to the American Jounal of Physics article. I probably need to read that a couple of times to really digest it, but there are a few things that this article validates on a more applicable level.

    (I like to think my students walk away from my lessons thinking, "Wow, that was interesting. Don really knows what he is talking about!". This is great information for me, but I already have a reputation for being too technical. If I integrate too much of this overtly into my lesson presentation, as true as I believe it must be, students may be really fascinated during my presentation, but as they don't get to "reread" that presentation, they will probably walk away saying, "What the hell was that about?!")

    So:
    1. Trying to hit your serve "harder" when you are serving really well will probably make the ball go slower, if not totally destroying your rhythm and effectiveness. Hit it "faster", not harder, by releasing more completely.

    2. On the groundstrokes, use the wrist as a "passive hinge" controlling the ball, but not snapping through it as you try to keep the strings on the ball as long as possible.

    3. In the same vein as the passive hinge, try to swing the racket head, not your arm or your hand. This means the wrist maintains its position and slight wrist cock as you swing forward to the ball on the forehand.

    4. On the other hand, this validates Phil's effort to emulate the Federer wrist extension/flexion flick at the beginning of his forehand forward swing.

    I do think we missed a whole lot of stuff here about internal rotation and the optimum angle of the racket shaft to the forearm to create effective power from internal rotation (you don't get much if the upper arm, forearm and racket shaft form a straight line...which they do in the frying-pan-grip-serve used by rank beginners). I wish we could get a comment from Rod about where that fits into the picture. Probably, I just need to do a little more reading in "The Physics and Technology of Tennis" (Is it in there, Julian?)

    Well, that's good for a start on Sunday morning. Curious to hear what the rest of you think.

    don

    Leave a comment:


  • julian1
    replied
    Another article by Rod Cross

    Originally posted by gzhpcu View Post
    Interesting article by Rod Cross...

    http://www.racquetsportsindustry.com...the_serve.html


    This is why we must aim high when hitting the serve and why the elbow remains high after impact on good serves...
    http://twu.tennis-warehouse.com/lear...lependulum.php
    To be exact it is really a paper describing a recently published article in American Journal of Physics by Rod Cross
    It has Paragraph 8 devoted to forehand
    Last edited by julian1; 06-12-2011, 10:09 AM.

    Leave a comment:


  • bottle
    replied
    No, after going to the court, my enthusiasm continues. This whole approach is very promising for a rotorded server like me-- but probably for anyone as well-- because of its emphasis on expanding range of motion. Steve in central Sweden was very quick to understand this.

    Of course there's no magic anywhere-- more like hard work-- but after doing every one of the exercises, I hit some serves that were almost satisfactory.

    I ask for several weeks before I deliver my official report, but I'm eager to explore this further. The hitch I recently introduced into my serve disappeared into thin air in a big hurry.

    I like experimentation anyway, and I've certainly been exposed to some of these ideas before, through Braden, Broudy and others, but not expressed the same way, and maybe not with such a clear emphasis on rolling the racket alternately this way and that to magnify each arm movement. Yes, the racket is always passing by the hand.

    It all seems to reflect a gradual acceleration rather than abrupt acceleration model.

    Do restricted rotors, headstrong tennis pros and snobby, obnoxious tennis players say that one's runway isn't long enough for their A-team? Well, who said the runway has to be straight? Who said the plane has to be a quick take-off Maule?

    More later. Thanks.

    Leave a comment:


  • tennis_chiro
    replied
    Wow

    Originally posted by bottle View Post
    Absolutely wonderful. THANK-YOU!
    Wow. An "absolutely wonderful" from Bottle. Nice way to start my day! Let's see what he says when he comes back from trying it out!

    don

    Leave a comment:


  • bottle
    replied
    Absolutely wonderful. THANK-YOU!

    Leave a comment:


  • tennis_chiro
    replied
    You have to try simple exercises to feel it

    Originally posted by bottle View Post
    Okay, Don, this is a good and very useful discussion for me personally-- for which I'm grateful-- but on the level of pure idea and the ideas to which we've all been exposed, isn't Rod Cross's essay a departure?

    I'm thinking of the various suggestions that teaching pros have always made to get us to accelerate racket tip the last little bit, maybe through braking action somehow from the opposite hand or an almost mystically abrupt change of direction or even a sudden shooting backward of one's tail.

    If I understand Mr. Cross correctly, he's saying what really does it is the butt of the racket twisting backward so powerfully (since it is on the short side of a fulcrum running through one's hand) that it actually retards huge movement already generated through centripetal force applied down the forearm toward the elbow.

    That part about retardation (Cross's phase three of acceleration) seems clear as does phase one, both of which involve a contest between the two pressure points on the handle, the one pushing forward, the other backward.

    I'm finding that Mr. Cross's insistence on this fulcrum idea from document to document is beginning to convince me-- he won't give up.

    If nothing else-- i.e., whether this information helps my own serve or not-- I'll know what he meant, and communication is good.

    It's with phase two-- which can generate a force equal to one's body weight-- that I need help.

    How specifically does one apply force down the forearm toward the elbow? With what body parts? I don't think I want to lower my head. The question ought to matter to anyone who at any time in their lives has delivered a resounding ace.

    Can Don or Steve or anyone help me understand this point?
    Okay, Bottle, I went through the Cross article once more. Try this

    You can't create the actions Cross is talking about with specific deliberate actions. (I think.) However, you can perform drills that include intrinsically the motions and actions that must be included in the total service motion to accomplish the effects Cross is talking about in the article.

    You will not generate those 150 lb. forces deliberately, but if you generate enough racket head speed and simply hold on to the racket (!), you are by definition exerting the necessary centripetal force to balance the centrifugal force the momentum of the racket head has created. If your wrist is relaxed while controlling the racket head, the racket face will direct a force perpendicular to this centrifugal force which powers the ball forward.

    So there are a few steps to this drill.

    First, you have to understand what my "Figure 8 drill" is. I think you are familiar with this but other members of the forum might not be. Just pretend you are making continuous swings standing in an alleyway extending to the target and there are 30 foot high glass walls on this approximately 2 foot wide alley. Here's a clip of the figure 8 drill.

    http://www.youtube.com/watch?v=gaS-qtQWym4&NR=1

    Unfortunately, I didn't have audio (I thought I did) when I made this recording. I need to update it and put some more videos up, but haven't done it yet. You could use this in conjunction with the positions demonstrated by Kerry Mitchell in his first service article

    http://www.tennisplayer.net/members/..._serve_part_1/

    Now, we get to the specifics of generating your increased racket head speed.
    We start with internal rotation.
    Stand facing the net with your upper arm next to your body and your forearm perpendicular with the racket shaft actually parallel to the baseline, the palm up, racket face horizontal and off to the right of your body. (for righties. Are you a lefty, Bottle? I mean left handed.) You can even rest your right elbow in your left hand.
    Without taking the elbow out of your left hand, rotate your forearm to the left so the racket face moves 180 degrees to where it is face down, palm down, but the face again horizontal, but on the opposite side of your body.
    Swing it back to the start.
    Now go back and forth as quick as you can without moving your right elbow out of your left hand.
    Optionally, you can go one stage further with this particular step by swinging the racket so far to the left that the face goes past horizontal and the shaft even begins to point down as it goes more than 180 degrees. At this point, you would be adding a little pronation and your elbow would pull out of your left hand.
    In any case, do this back and forth as fast as you can. Feel the internal rotation and how the racket head goes past the wrist.

    Now you try to take this feeling into doing the aforementioned Figure 8's. Try to "whistle" the racket at its highest point in the swing, just at or after contact. Next try it actually hitting the ball.

    Want more?

    Stand with a slightly open stance at about 45 degrees to the baseline (because this is an abbreviated motion and you won't have the benefit of a full swing to turn the hips and shoulders forward from the normal starting position).

    Position yourself so the shoulders are actually parallel to the baseline (or even perpendicular to the intended path of the ball).
    First put the racket face up to the contact point. (Remember the racket is not straight up. For a righty, the forearm and the racket shaft form a 10 to 20 degree angle at contact. Just guessing on those numbers. Check with John and Brian's data.)
    From the contact point, while leaving the elbow exactly where it is pull the racket head back down as you externally rotate as you reverse the internal rotation that took the racket up to the ball.
    Now, while leaving the elbow where it is, swing the racket head up to the contact point and past to the "Sampras racket head down" point. Now swing the racket back and forth along this path. It's kind of like what we were doing in our first exercise here, but a little different.

    Note: it is important that at the starting point of this motion the butt of the racket is pointed like a flashlight at the ball and also in the direction of the target. Most people have to be corrected from a position where they have the shaft of the racket pointed too far to the right and they are unable to generate sufficient force in this swing in the direction of the target to get the ball over the net.

    Once you get a little feel for it, starting from that point with the elbow up in front of you, toss and "tap" the ball over the net. Range of motion and a "clean" contact is the goal here, not speed.

    When you feel you can do that a little bit, try to incorporate the feeling into the figure 8 drill. See if you can get a little more "whistle". But don't worry too much about speed in the actual hit just yet. "Hard" is your enemy right now. "Relaxed" is your friend.

    Now we go to the next step. Maintaining the same stance position you had in the last drill (about 45 degrees open), go to the "trophy" position. Now see if you can toss the ball (always transfer your weight forward as you toss the ball; you don't get to use your normal backswing, but you can still have a little rhythm with a rock or just a back to front shift as you toss the ball) and then do the last drill from "trophy" position and still finish with the right elbow up and the "Sampras racket head down" ending…literally. Of course, that means you can't swing too fast; but you can still propel the ball a little faster than we did in the initial version of this drill.

    Now if you can feel this, you can try and put that feeling into the Figure 8 and go for even more "whistle".

    Bottle, all this is pretty removed from what Rod Cross was pointing out. But one key to doing this drill is that the wrist must be in control, that it is it must have the racket handle snug in the hand and against the heel of the hand; at the same time, the wrist must be completely relaxed and just acting as a hinge to allow this full range of motion. Certainly, there will be some wrist flexion and ulnar deviation involved as you move the racket head up to the ball, but the true primary forces are going to be coming from other elements.

    And finally, if you can put all this together and feel a little more racket head speed and get the "whistle" to happen at the right time (up through impact and just beyond), you will be forced to exert significant centripetal forces to overcome the momentum and forces of the racket as it swings up to the ball; thereby you will have to do what Rod Cross is describing in his article. But I don't think you will be able to accomplish that if you try to "exert centripetal force on the handle of the racket with a vector at the heel of your hand counter to the vector exerted at the first knuckle and the fingers". Not going to happen!

    Good luck with it, Bottle. And Phil, you might try this too. And Ed, did you get this down?

    good night,
    don
    Last edited by tennis_chiro; 06-08-2011, 11:03 PM. Reason: clarity; clarification

    Leave a comment:


  • bottle
    replied
    Okay, Don, this is a good and very useful discussion for me personally-- for which I'm grateful-- but on the level of pure idea and the ideas to which we've all been exposed, isn't Rod Cross's essay a departure?

    I'm thinking of the various suggestions that teaching pros have always made to get us to accelerate racket tip the last little bit, maybe through braking action somehow from the opposite hand or an almost mystically abrupt change of direction or even a sudden shooting backward of one's tail.

    If I understand Mr. Cross correctly, he's saying what really does it is the butt of the racket twisting backward so powerfully (since it is on the short side of a fulcrum running through one's hand) that it actually retards huge movement already generated through centripetal force applied down the forearm toward the elbow.

    That part about retardation (Cross's phase three of acceleration) seems clear as does phase one, both of which involve a contest between the two pressure points on the handle, the one pushing forward, the other backward.

    I'm finding that Mr. Cross's insistence on this fulcrum idea from document to document is beginning to convince me-- he won't give up.

    If nothing else-- i.e., whether this information helps my own serve or not-- I'll know what he meant, and communication is good.

    It's with phase two-- which can generate a force equal to one's body weight-- that I need help.

    How specifically does one apply force down the forearm toward the elbow? With what body parts? I don't think I want to lower my head. The question ought to matter to anyone who at any time in their lives has delivered a resounding ace.

    Can Don or Steve or anyone help me understand this point?
    Last edited by bottle; 06-08-2011, 02:57 PM.

    Leave a comment:


  • tennis_chiro
    replied
    Perhaps

    Originally posted by bottle View Post
    Okay, now I've tried it, or rather tried all of this information taken together.
    ...

    Maybe the answer is to start throwing toward the moon, but just before your arm detaches from your body pull it back in?

    And, of course, stay loose throughout?
    If you didn't do this at least a little bit, perhaps subconsciously, I think you might fracture the elbow at the ulna. You have to "release" through impact. Good servers learn to hit their fastest serves by "releasing". Tensing up and swinging "harder" only makes the ball go slower. This is one of the big challenges you face when you are serving really well. You think you are hitting it so well that maybe you can try to swing even just a little harder. In that moment where you go just a little too far and the muscles take over, it all falls apart.

    So yes, stay relaxed throughout (maybe not loose). More like a rollercoaster car that moves freely through its turns, but definitely on a track.

    Good luck with it,
    don

    PS I'd be really careful of using any images that involve hitting down. That may be reality for someone as tall as you are, but you really are better feeling like you are hitting up.

    Leave a comment:

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