The Forehand: Busting misconceptions once and for all

Discussion in 'Tennis Tips/Instruction' started by 10isfreak, Jan 11, 2013.

  1. sureshs

    sureshs Bionic Poster

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    If some shots are hit below center, it is probably as a by-product of other factors like closed face and whether the ball is rising or falling , etc.
     
  2. Chas Tennis

    Chas Tennis Hall of Fame

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    You can do some analysis with a DVR when a high speed video with small motion blur is shown. With the Motorola controller pause just before ball impact, then press the pause button again to advance a single frame. Works great.

    I was watching the Australian Open yesterday and they had a slow motion of Tipsaravic hitting a forehand. Contact was very close to the centerline.

    Interpretation of Videos - For the Tipsaravec video the racket was rising so rapidly that just one frame time after impact, the ball appeared distinctly below the racket centerline. I do not know the frame rate (and there was a degree of double imaging (interlacing?) in my DVR stop action display of the broadcast). But frame rate could be an issue that causes errors that would falsely skew the data to below center hits if you catch the ball later, say, when it has just left the strings. That error would falsely add to counts below the centerline. This issue applies, of course, to all high speed video analysis.

    Toly, those are great pictures, the perfect display for this issue. I would like to learn how to do that. Since you have found a great way to display frames could you tell us the expert's way to capture an image from video, assemble images, label, and post them into the forum?
    Such as
    1) View Youtube or other?
    2) Use some kind of YT frame capture or download video and use which other software to capture a single frame from the video.
    3) What video software or other software did you use to assemble the selected frames and label them?
    4) Did you prepare the assembled pictures and upload them to an internet photo site and then entered the URL link in the box available ("Image Insert") on the TW forum reply page?
     
    Last edited: Jan 20, 2013
  3. corners

    corners Legend

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    Wait a minute, who's cheating? At least he posted his evidence, as scanty as it may be. You simply refer to the "100s" of videos you have seen and that we have not, of which you estimate that 50% are below the longitudinal axis. Toly has no agenda here, he's just looking at some video and posting what he finds, which takes some time BTW, even though its only a small sample. You do appear to have an agenda, or at least some investment into this idea, an investment you're trying to protect apparently. Presumably you've spent some time trying to figure out if you're correct or just fooling yourself, right? But you haven't even taken an accurate count of the "100s" of below center impacts you claim to have observed. Is that good enough to convince you you're right? It's not gonna convince anyone else, that's for sure.
     
  4. corners

    corners Legend

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    Yeah, the ball will always be below the impact point immediately after impact on topspin shots because the ball is sliding along the strings at that phase of impact. But the lab evidence found that balls that strike below center rebound with more spin, not balls that slide down there. So when viewing video the only thing that counts, given the information we have currently, is where the ball first touches the strings, because that corresponds with where the ball was aimed in the lab.

    Again, for those who haven't seen it, the lab evidence I'm referring to: http://twu.tennis-warehouse.com/learning_center/location.php
     
  5. corners

    corners Legend

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    Peliwo gives a very astute and educated response. He's not 100% sure about most of this stuff because he hasn't analyzed the video. Smart guy. But the takeaway, as far as this thread goes, is that he dosen't aim below center, or at least he doesn't aim below center consciously. Sample size = 1, yes, but now we know that one pro does not hit below center on purpose.
     
  6. Relinquis

    Relinquis Hall of Fame

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    ultimately what are you going to do with this knowledge? apply it, right?

    why don't you guys go out to a court and try your theories? see what happens trying to hit below or above or on the centre during practice rallies and then during a match. Report back, maybe with a bit of video.

    this forum isn't a peer reviewed academic journal. you're just arguing without having done a controlled experiment nor have you gathered empirical data systematically. What are you trying to prove apart from being keyboard warriors?

    You're not advancing anyone's understanding with your tone and arguments.
     
  7. Chas Tennis

    Chas Tennis Hall of Fame

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    The pros impact first on the strings above, on, or below the racket centerline. The stats are out there now in the high speed videos, on your DVR or even in a sample of still photographs of forehand ball impacts. It is a simple enough observation that with some care we might get a preliminary result.

    Why not?

    Even better, someone might find and present some existing research on this interesting question.
     
    Last edited: Jan 20, 2013
  8. toly

    toly Hall of Fame

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    1) View Youtube or other?
    Mostly YouTube, but also some different websites.

    2) Use some kind of YT frame capture or download video and use which other software to capture a single frame from the video.
    Use RealPlayer (it is free) to download and trim video.
    Use Kinovea (it is free) to save particular frame of video as picture with JPEG extension.


    3) What video software or other software did you use to assemble the selected frames and label them?
    That can be any drawing application, for example: PaintBrush, PowerPoint, and Photoshop.

    4) Did you prepare the assembled pictures and upload them to an internet photo site and then entered the URL link in the box available ("Image Insert") on the TW forum reply page?
    I use tinypic.com (it is free). :)
     
    Last edited: Jan 26, 2013
  9. sureshs

    sureshs Bionic Poster

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    I did a minor adjustment today which fixed a backhand issue (for good I hope). I consciously made sure that the racket face was closed on take back. It seems much easier to start with a closed face and go more open later, than vice versa. I realized that I always had a closed face on my forehand, but not on my backhand. Then I noticed several players today making the same mistake and hitting weak or long backhands (but I did not tell them about it).
     
  10. luvforty

    luvforty Banned

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    this below the sweetspot stuff, may have merit, but practically useless..

    i be happy if i put the racket on the ball.
     
  11. corners

    corners Legend

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    LOL. Me too.
     
  12. Chas Tennis

    Chas Tennis Hall of Fame

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    MYTH: Step forward to put your 'weight' into the shot.

    REALITY: Your weight is the magnitude of the force from earth's gravity that attracts you to earth. [A vector has both magnitude and direction.] The force is a vector that is always directed toward the center of mass of the earth, down. How am I putting 200 lbs into the shot?

    SPECULATION: You move your mass into the court by stepping forward while and at the same time rotating or moving some body parts back in the backswing. In this way you pre-stretch some useful muscles using the inertia of both body parts & the racket relative to your center of mass and deliberate muscle activation. Those pre-stretched muscles can then forcefully, rapidly, smoothly and maybe more reproducibly shorten to produce a large portion of the racket head speed. If you don't get you mass moving into the court by stepping the pre-stretching of some of these muscles is much less effective.
     
    Last edited: Jan 21, 2013
  13. luvforty

    luvforty Banned

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    no.. gravity always down doesn't mean it can't help creating forward momentum.

    from standing still, how do you start walking forward? you don't just start pushing with your feet..... you actually first move your CoG forward by 'falling forward', the you move your feet to 'catch yourself' to start walking.

    you can put you weight into the shot... not the entire 200lbs though.
     
  14. Chas Tennis

    Chas Tennis Hall of Fame

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    Roughly how much of my weight do you think I can put into my shot?
     
  15. 10isfreak

    10isfreak Semi-Pro

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    Well, I doubt that they can really go out on a court and test their hypotheses. By the way, the concept of "theory" in a scientific context involves a test or a series of test: a theory is a validated hypothesis or a collection of these.

    But I agree with your point. Without data, we cannot make the right call. When I initiated this thread, I used the blog of a researcher to present simple principles that we can all apply in our everyday lives. As a fact lower contact do lead to higher spin rate, but whether this is manageable for a player to get is a different question... maybe they are results of slight differences in the player's movement as "dominik" suggests, maybe not.

    The only important point is that what the best pros do on the court to hit good forehands differs a lot from what we read on this forum or even hear by sometimes famous coaches and knowing these distinctions between the factual reality and the doctrines which are professed by people such as Wegner can enable you to make a difference in your game.
     
  16. 10isfreak

    10isfreak Semi-Pro

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    The vast majority of strokes do not involve forward movement, although it is clear that you can more easily hit a better shot by moving forward. As you pointed out, the wording is both confusing and wrong regarding this phenomenon.

    As a matter of fact, many micro movements enable players to benefit of specific muscular reflexes that makes it easier to reproduce the stroke every time, all the while making themselves more powerful. A muscle which is fully extended will contract faster, provided that this extension doesn't last long: you have a window of half a second to use it to enhance your performances.

    We call this phenomenon a stretch-shortening cycle because the muscle goes through a cycle of eccentric and concentric contraction which enables the individual to shorten the amount of time required to perform the concentric contraction. It seems complicated, but eccentric and concentric just means "toward the exterior" and "toward the center." A muscle eccentrically contracts when the antagonist muscle forces the muscle into extension (for instance, your biceps forces your triceps into eccentric contraction when you use them to lift a weight). Isometric just means holding stuff into place, like trying to sit on a fake chair to train your leg muscles.

    End of the parentheses. Your point does present an issue... You do not have to be moving forward to benefit of these cycles. Some of them involve muscles which have nothing to do with your body's position or where it is heading. In fact, you can hit just as hard while moving backward than moving forward... just as you hit a 100 mph running forehand.

    The only difference is that moving backward involves a different set up which is, upfront, less usual or common. If you practice it, you can do it right, though and it's pretty similar to hitting an airborne forehand such as what Federer likes to do. The key is that you find a way to use your last step to begin your motion. On every version of the running forehand, of the airborne forehand, of the forehand approach shot or while moving back... every one of them can be hit with the same overall motion. The point is that you need, as if you were standing still, to begin with your racket leg -- you need to use it in order to begin your hip rotation. That's the key to ALL forehand strokes which involve complex footwork.

    In terms of hitting it, you're still rotating just the same and you're still enjoying plenty of sources of power. It simply requires a more complex sequence of action and it can be more easily thrown off than, say, if you were hitting forehand without having to move.
     
  17. 10isfreak

    10isfreak Semi-Pro

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    It's a simple thing which makes a lot of difference in terms of control and pace. With the safety of additional spin, people can hit out a lot more loosely. Furthermore, spin confers control over the ball's placement.
     
  18. sureshs

    sureshs Bionic Poster

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    The spin was there - it was more like the closed face made it easier to be consistent than sometimes starting with a slightly open face and then closing it. By always closing it, or leading with the edge as Oscar says, you can open it up a little if you want to.
     
  19. Chas Tennis

    Chas Tennis Hall of Fame

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    Better to say- Translate you body and your joints in a way to stretch the muscles used for the forehand.
     
    Last edited: Jan 21, 2013
  20. Kevo

    Kevo Hall of Fame

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    Most people use weight and mass interchangeably. So moving forward to put your weight into the shot is fine IMO. It's not necessarily the new school way to hit the ball, but it does work quite well. I've hit many winners while moving forward into the shot.

    Also, hitting the ball with your weight(mass) moving forward rather than swinging makes for some of the most spectacularly power volleys I have ever hit. It's amazing really how much hurt you can put on the ball with a step forward and a slight forward movement of the racquet. It's really a shame I don't typically move properly up to net and I like to swing too much.
     
  21. Chas Tennis

    Chas Tennis Hall of Fame

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    I agree.
    An instruction video, Volley Secrets, that supports the view of step forward as you volley.
    http://www.youtube.com/watch?v=fJb954_II7c

    Why do you think moving forward relatively slowly at maybe 10-15(?) feet per second, slow compared to the ball velocity, adds so much stick to your volley?
     
    Last edited: Jan 21, 2013
  22. Chas Tennis

    Chas Tennis Hall of Fame

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    CORRECTION: On this video I could use the forward and backward arrows to do stop action single frame on Youtube. A huge improvement for analyzing high speed videos of tennis strokes.

    See second 27 for Almagro contacting the tennis ball.
    http://www.youtube.com/watch?v=ekb4AqquFL8
     
  23. Kevo

    Kevo Hall of Fame

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    I believe it's a combination of things, but the basic answer is when the form is correct the ball sees not just the mass of the racquet and arm, but much of the bodies mass as well.

    Think of it like getting hit by a cyclist at relatively high speed versus getting hit by a truck at low speed. The energy from a massive object even at slow speed is much higher.
     
  24. luvforty

    luvforty Banned

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    body moving 10 ft/sec.... but the arm is also moving forward, so the combined speed is bigger.

    body moving forward is more of a necessity to find the ball.... i can hit a volley almost equally hard without body moving forward if the ball is within reach.

    you do swing to hit a penetrating volley.... but beginners swing the wrong thing.. they move the racket head, but the elbow is almost static, so there is no mass behind the collision.

    Oscar has a video about 'leading with the hand'... it works for his teaching... but i would teach 'moving the elbow at the same speed as the racket head'..... this way you keep the face angle the same, and you have mass in the collision.

    with a firm grip, let's say the collision is almost elastic.

    then

    m1v1 + m2v2 = m1v1' + m2v2'

    and

    1/2 m1 v1 (sq) + 1/2 m2 v2 (sq) = 1/2 m1 v1' (sq) + 1/2 m2 v2' (sq)

    in other words, conservation of momentum and kinetic energy.

    and you can plug in a few numbers, and realize that to achieve the maximum v2' (ball speed), the key is to increase m1 !

    so you make the collision unit bigger, not just the racket head, but the entire arm/racket unit.
     
  25. Chas Tennis

    Chas Tennis Hall of Fame

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    Last edited: Jan 28, 2013
  26. Chas Tennis

    Chas Tennis Hall of Fame

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    Impact Location on Racket Face from Australian Open TV

    Stop Action with DVR. I looked at the clear high speed videos presented on the 2013 Australian Open by ESPN & Tennis Channel. I used my DVR to do stop action. Both ATP & WTA players. Only used videos that were clear with small motion blur. (Rejected double image effects probably due to unknown interlacing effects). Record keeping was poor, about 10-12 total.

    These videos were usually winner highlights, where the players appeared to be in good position and intended to hit a very strong forehand. I don't believe that any were of shots that went out.

    If the bottom/lowest frame edge of the racket were 0, the top/highest frame edge were 10 and the center line (handle center line extended) were 5 then

    the ball hits were in the 4-6 range. I did not see any impacts that were way off the centerline.

    Estimating impact spot, where 5 is the center line and the racket face is divided 0-10 bottom to top:
    Li Na - 5, 6
    Sharpova - 4, 5
    Tipsaravic - 4
    Some others also.....

    I had intended to analyze more high speed videos shots just as Toly has done but have not gotten to it.

    I had originally thought that pros deliberately or by trial-and-error practice were hitting most balls in the lower half of the racket face (say at 3 as defined above). Now I don't believe that. I intend to farther analyze videos for this issue as I come across them. The issue could be farther researched.

    High Speed Video Analysis Issue- Racket is Rising Rapidly at Impact. One point is that for the current forehand with its rapid rise of the racket at impact, when you look at a high speed video and see ball impact, on the very next frame at 200-300 fps the racket will will have moved considerably higher. Not doing single frame analysis may produce a false conclusion as to where the ball was on the racket face at impact. Requires targeted high speed video with a clear view of the racket face, high frame rates >200 fps ?, a fast shutter speed for small motion blur, and observing ball impact on the strings. Any rolling of the ball on the strings makes analysis less accurate. Both the rapid racket motion up and the ball rolling on the strings might make the ball appear to initially hit low on the racket face if not carefully measured. I think that's what fooled me.

    An interesting related question - Do I hit long and in the net because I am hitting high or low on the racket face - much more than the pros do - and the racket tilts while in contact?
     
    Last edited: Jan 29, 2013
  27. HSCoach

    HSCoach New User

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    I expect we know the above is the case. For this discussion, if a ball contacts the strings in the exact center, then slides a couple of mm down during the dwell time, would you call that a center hit or below center hit? thanks.
     
  28. Chas Tennis

    Chas Tennis Hall of Fame

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    I'm not sure who you are asking. I proposed a question only about the initial ball contact location, first contact, and a simple way to crudely observe it with videos.
    If we had observed lower impact points then it would be interesting and need better measurements with higher speed cameras to see the entire ball contact time. Videos of this quality are probably not available for pros on the internet, Nadal's entire contact time at 5000 fps, etc.

    I would call your example a center hit, a 5. The accuracy of these crude measurements is not expected to be "a couple of mm", it's probably not even +/- 2 cm. I divided the racket face width into 10 parts and estimated by eye which part it mostly hit in. My racket face is 27 cm across and 1/10th of that would be 2.7 cm. Saying it hit at 6 means that it is estimated to be closer to 6 than to 5 or 7.

    This is just a crude measurement intended for a quick look to see if the balls were systematically hitting low, say, around 3 which was my best guess before looking more carefully at some videos.

    This little myth may have cost me because I actually thought hitting in the bottom half might work better than hitting in the top half or centerline. It still might for my stroke if the racket tilt after impact has some affect. Next, I will be looking for how far off the center the hits are and how the racket tilts.
     
    Last edited: Jan 29, 2013
  29. HSCoach

    HSCoach New User

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    thanks for your answer and I agree this is a challenge with most available video. With high speed video on strong top spin shots, there are 2 points of reference (at least) for us. One is the initial contact you suggest and the other is location at full pocket depth. seems the full pocket depth is lower and more indicative of the action you expect.
     
  30. Relinquis

    Relinquis Hall of Fame

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    Surely the greater forehand misconception is that players are able to hit the ball 1-2 cm below the centre of the racquet consistently...
     
    Last edited: Jan 29, 2013
  31. sureshs

    sureshs Bionic Poster

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  32. HSCoach

    HSCoach New User

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  33. JonC

    JonC Banned

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    Interesting, perhaps a reason for looser strings.
     

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