"Accelerate evenly through the ball"

Discussion in 'Tennis Tips/Instruction' started by Bergboy123, Apr 27, 2012.

  1. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
  2. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    Last edited: May 9, 2012
  3. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
  4. Cheetah

    Cheetah Hall of Fame

    Joined:
    Mar 29, 2011
    Messages:
    3,877
    Location:
    San Diego
    5263,

    Do you teach your students to accelerate at the last moment as opposed to accelerating throughout the full forward swing?
     
  5. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    I don't like the "last moment" terminology and would say there is a very gentle accel
    during the early part, with a greater amount at the "right moment". :)
     
  6. Cheetah

    Cheetah Hall of Fame

    Joined:
    Mar 29, 2011
    Messages:
    3,877
    Location:
    San Diego
    ... and that 'right moment' would be ... say the last 25% or less of the distance from slot position to contact? something like that?
     
  7. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Something like that depending on your definitions and intentions, but it's a timing thing and based on having nice contact lined up and assured.
     
  8. Cheetah

    Cheetah Hall of Fame

    Joined:
    Mar 29, 2011
    Messages:
    3,877
    Location:
    San Diego
    ok. was just wondering. i've been having good results recently having most of the acceleration in the latter part of the swing.
    Doesn't oscar/mtm say you should increase acceleration right before contact?
     
    Last edited: May 5, 2012
  9. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Something like that. We sort of have to be careful with the wording, as many
    will try to say we are accelerating late, but late as in too late, can't be good, right? lol:???:
    I think you have it right, as in later part of the stroke.

    I agree that it is later in the stroke though and it's termed finding the ball with
    the hand first, then there is an exchange by the accel of changing directions with
    the hand "up and across" where the hand that lined up the ball is now exchanged for the bringing the racket face to bear. It is so beautiful when
    done well! and helps with that accel at the right time effect.
    This is different than the racket head speed approach, where the harder accel must take place way earlier to seek higher racket head speeds.
    Make sense?
     
  10. toly

    toly Hall of Fame

    Joined:
    Sep 2, 2010
    Messages:
    1,993
    Again I don’t understand anything.

    What exactly should the hand do to create “up and across” motion of the racquet?:cry:
     
  11. Cheetah

    Cheetah Hall of Fame

    Joined:
    Mar 29, 2011
    Messages:
    3,877
    Location:
    San Diego
    yea i got it. i already hit hard but but this little adjustment seems to be giving me a little more pace. it feels better/different. since i've been doing it i think i can actually see now that the pros most of the time are doing this.
     
  12. chico9166

    chico9166 Guest

    I really like the concept/feeling/advocation of a more later acceleration (closer to contact) of the racquet. One of the residual effects (at least in my experience) is a more relaxed, tension free backswing, and change of direction of the racquet. A real important, overlooked, aspect of tempo, timing, and good contact. Too many try and access speed too early and with too much force.

    If you look at good players, as they trek and line up the ball (and move through there backswing and change of direction) the motion is relaxed, continuous, and with only mild acceleration. As they start to pull and turn into the line of the shot, all hell breaks loose as they "commit" to releasing the racquet. This is where the bulk of acceleration occurs.

    Accelerating close to contact is a good conceptual model, IMO.
     
    Last edited by a moderator: May 6, 2012
  13. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Using the body to power it, the hand leads the way by going up and across, as the racket lags doing a similar but wider path like a water skier outside the wake in a turn.

    Took me awhile to see it as well, because I, like you, before used the wrist to drive the racket tip and face around, keeping it or catching it up to my hands arc opposed to using this dragging effect.
     
    Last edited: May 6, 2012
  14. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Excellent post IMO.
     
  15. toly

    toly Hall of Fame

    Joined:
    Sep 2, 2010
    Messages:
    1,993
    Do you mean that the hand/wrist does not do anything by itself, and should be stable (frozen) with respect to the axis of the forearm?:confused:
     
  16. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    Internal rotation of the upper arm:the missing link in the kinetic chain

    A bit related
    http://w4.ub.uni-konstanz.de/cpa/article/viewFile/2695/2533
    The important quote:
    "The summation of speed principle states that to maximise the speed at the distal end of a linked system, the movement should start with the more proximal and progress to the more distal segments, such that each segment starts its motion at the instant of greatest speed of the preceding segment and reaches a maximum speed greater than that of its predecessor (Bunn, 1972)."
    Please see the picture and the curve with CIRCLES
    see as well
    Aust J Sci Med Sport. 1996 Dec;28(4):106-13.
    The role of upper limb segment rotations in the development of spin in the tennis forehand.
    Takahashi K, Elliott B, Noffal G.
    Source

    Faculty of Education, Saitama University, Japan.
    Abstract

    Increased topspin in the tennis forehand is produced by maintaining a perpendicular racket-face to the court surface at impact and increasing the trajectory and vertical velocity of the racket-head. These modifications to stroke technique from those previously identified in the flat forehand drive are the result of changes to the movement patterns of the segments of the upper limb. The contributions that the upper limb segment's anatomical rotations make to racket-head velocity at impact depend on both their angular velocity and the instantaneous position of the racket with respect to these movements. Six high performance tennis players were filmed at a nominal rate of 200 Hz by three Photosonics cameras while hitting flat (no spin) and topspin groundstrokes and a forehand topspin lob. The three-dimensional (3-D) displacement histories of 16 selected landmarks were then calculated using the direct linear transformation approach and 3-D individual segment rotations for the upper limb were calculated using vector equations. Significant differences were recorded in the effect that the various segment rotations made to the x-direction (forward) and y-direction (upward) impact velocities of the racket-head. These differences were not reflected in the contributions to racket-head velocity when the absolute velocities were expressed relative to the impact velocity. Trunk rotation, upper arm flexion/abduction, upper arm internal rotation, hand palmar and ulnar flexion all played integral roles in producing impact racket speed.
    http://www.tandfonline.com/doi/abs/10.1080/02640419608727697#preview
    http://w4.ub.uni-konstanz.de/cpa/article/view/2228/2085
    http://evidence.unboundmedicine.com...elocity_at_ball_impact_during_tennis_serving_
     
    Last edited: May 6, 2012
  17. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Do nothing or frozen would be an overstatement to one extreme, but maybe describing the effect is a challenge, especially if you don't have the swing motion
    understood. I look at the wrist more like a spring that closes the screen door on my porch.
    This wrist spring has enough flex to let the racket lay back a bit due to force of
    forward stroke, but does not at any time have to force to overcome this force.
    It is only when the force is removed due to the change of direction of the hand
    and is replaced by centrifugal force to bring the racket face around, that then the wrist spring can be a part of the hand coming back to more of a neutral position much like it was before being laid back, resulting in the racket catching up
    some to alignment with the forearm. (but not all the way)
    The wrist is not driving this "catch up" if you will, as the change in hand position and centrifugal force are, but more of stabilizing nature to keep it from just flopping between the stops like a door with NO spring. The wrist just
    offers a tension control aspect.

    Yes, player do pop at the ball with their wrist, but it causes all sorts of timing problems and
    only works well in the best circumtances and accounts for much of where we see Fhs break down under pressure.
     
  18. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Yes, Important quote to express the confusion on the topic. This and toly seem
    to be on the same page of misunderstanding about tennis Fhs.

    In high level tennis the Fh needs to be as fast as it can be while staying "bomb proof"!

    This means we want all the power and spin we can get, as long as we can stay very consistent AND handle what is coming from the other side. Quite
    different from a true max effort scenario.

    We Must keep the control factors as a high priority with any technique we develop for tennis strokes.
     
  19. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

    Joined:
    Feb 25, 2006
    Messages:
    11,055
    Location:
    Stuck in the Matrix somewhere in Santa Clara CA
    Excellent resource, julian. The angular velocity graphs for the elite golf swing looks very similar to the double pendulum tennis swing model from Rod Cross. For the elite golf swing, the pelvis followed by the thorax and arm/hands achieve their maximum speed somewhat before impact. At impact, the club head speed is at its greatest while speed of the the thorax and hands have decreased to a relative minimum. As a result of the impact, the club head speed drops dramatically for a while (but then rises back to a relative max before dropping off again).

    http://www.mytpi.com/images/pdfs/Kinematic%20SequenceTransitionDownswing.pdf

    Acceleration Variations (Observations in the Kinematic Sequence)

    .
     
  20. sureshs

    sureshs Bionic Poster

    Joined:
    Oct 1, 2005
    Messages:
    35,055
    He says that there is an abrupt change in direction/angle/something just before contact, which kind of sounds opposite to the above, and does not seem right to me. He asked me to comment on it because it was in his daily tips, and when I did (along with a bunch of other comments), he never answered that post.
     
  21. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

    Joined:
    Feb 25, 2006
    Messages:
    11,055
    Location:
    Stuck in the Matrix somewhere in Santa Clara CA
    Another very good resource here. I really connected with one of the opening comments:

    "One of the most common mistakes made by coaches and athletes is to imitate the techniques of professional players... Hay (1993) suggested that many professional players succeed because of their physical attributes not because of their optimal techniques. In other cases, players develop idiosyncrasies - unique aspects of the players' strokes that do not contribute to the strokes (Groppel, 1992)."


    There is quite a bit of other information here as well. WRT the follow-thru:

    "The lack of or a short follow-through would cause the racket to slow down prior to impact."

    It appears, however, that this article may have been written in the early '00s. The most recent references are from the late 90s. This was before the rise of the popularity of the windshield wiper FH. This was the late Sampras-Agassi era before the rise of Federer & Roddick (and later, Nadal & Djokovic). There is much discussion of the multi-segment forehand technique. I recall this is something of a "modern" (teaching) technique in the 90s. (Refer to the Tennis 2000 videos that were released in the 90s).

    They speak of the FH swing path angle ranging between 17º and 47º from the horizontal (Groppel, 1992). The optimum angle ... has been suggested to be 28º. This sounds like the swing path of an OTS follow-thru rather than a WW swing. I recall Vic Braden mentioning somet time ago that Agassi's flat FH swing path was close to 20º while clay courters were closer to 45º. From the Coaches Info article, we get the following quote:

    "Smaller angles tend to produce less spin, while larger angles sacrifice ball speed and depth of the shot."

    With the rise on popularity of the WW forehand, we are now seing players who can generate ball speed and shot depth with high trajectory swing paths.
     
  22. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

    Joined:
    Feb 25, 2006
    Messages:
    11,055
    Location:
    Stuck in the Matrix somewhere in Santa Clara CA
    Excellent resource, julian. The angular velocity graphs for the elite golf swing looks very similar to the double pendulum tennis swing model from Rod Cross. For the elite golf swing, the pelvis followed by the thorax and arm/hands achieve their maximum speed somewhat before impact. At impact, the club head speed is at its greatest while speed of the the thorax and hands have decreased to a relative minimum. As a result of the impact, the club head speed drops dramatically for a while (but then rises back to a relative max before dropping off again).

    http://www.mytpi.com/images/pdfs/Kinematic SequenceTransitionDownswing.pdf

    Acceleration Variations (Observations in the Kinematic Sequence)

    .
     
  23. Cheetah

    Cheetah Hall of Fame

    Joined:
    Mar 29, 2011
    Messages:
    3,877
    Location:
    San Diego
    i don't know. but what i do is accelerate to the ball as usual, perhaps a little slower than i used to prior to utilizing this method, and just as the butt cap passes by the ball before the ball is struck i accelerate to max speed. it feels pretty good. feels kind of more 'professional'. gives a little more bite. one of my regular partners said 'it looks more intimidating'. haha. whatever that means.
     
  24. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    Is the E-mail working?

    SystemicAnomaly,
    Is the E-mail feature of this forum working succesfuly?
     
  25. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    You may want to see other articles at this Web site

    You may want to see other articles at this Web site -but probably you did do it already
     
    Last edited: May 7, 2012
  26. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

    Joined:
    Feb 25, 2006
    Messages:
    11,055
    Location:
    Stuck in the Matrix somewhere in Santa Clara CA
    ^ Thnx, Julian. Just replied to your email. Have briefly looked at another article. Some very good stuff there.

    (Note: I've got more to say WRT to double pendulum. Stay tuned).


    .
     
    Last edited: May 7, 2012
  27. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Sound good Cheetah and smooth & simple too, eh.
     
  28. Cheetah

    Cheetah Hall of Fame

    Joined:
    Mar 29, 2011
    Messages:
    3,877
    Location:
    San Diego
    played today using this acceleration method again. it's good. i've found out it has several other 'hidden' benefits too.
     
  29. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    A multi-sensory approach to PERFORMANCE ANALYSIS IN TENNIS

    TENNISSENSE: A MULTI-SENSORY APPROACH TO PERFORMANCE ANALYSIS IN TENNIS
    Luke Conroy1, Ciarán Ó Conaire2, Shirley Coyle2, Graham Healy2, Philip Kelly2, Damien Connaghan2 Noel E. O’Connor2, Alan F. Smeaton2, Brian Caulfield1, Paddy Nixon1
    CLARITY Centre - University College Dublin1 & Dublin City University2, Ireland
    KEY WORDS: Accelerometer, Tennis, Stroke, Coaching
    INTRODUCTION: There is sufficient evidence in the current literature that the ability to accurately capture and model the accelerations, angular velocities and orientations involved in the tennis stroke could facilitate a major step forward in the application of biomechanics to tennis coaching (Tanabe & Ito, 2007; Gordon & Dapena, 2006). The TennisSense Project, run in collaboration with Tennis Ireland, aims to create the infrastructure required to digitally capture physical, tactical and physiological data from tennis players in order to assist in their coaching and improve performance. This study examined the potential for using Wireless Inertial Monitoring Units (WIMUs) to model the biomechanical aspects of the tennis stroke and for developing coaching tools that utilise this information.
    METHODS: The TennisSense Technology Infrastructure comprises a UbiSense Spatial Localisation System and a Wireless Inertial Monitoring Unit (WIMU) worn on the forearm (racquet arm) of the player, that records acceleration, angular velocity and orientation in all three axes; using accelerometer, gyroscope and magnetometer sensors respectively. In addition, a total of nine cameras are positioned around the court, with pan, tilt and zoom capability. We recorded five separate training sessions of 20 minutes duration, using a single WIMU on the player’s forearm, the UbiSense System and the full nine camera rig.
    RESULTS & DISCUSSION: For this initial study, we looked solely at the accelerometer data from the WIMU that was synchronised with the camera data. The data was graphed using MATLAB® and compared to the video data. The most useful sequences of data were training drills; where the player attempts to reproduce an identical shot each time. It was clear from a manual inspection of these drill sequences; that significant similarities existed in the graphed accelerometer data between correctly executed shots of an identical type.
    CONCLUSION: This examination of the results leads us to conclude that accelerometer data from 1 or more on-body sensors, could be readily used in a tool to automatically identify shot type, shot quality and subsequently the biomechanical determinants of correct/incorrect technique; based on a golden template of accelerometer data with appropriate matching criteria. The utility of such a tool is inferred from the literature examining the contributions of biomechanical factors to tennis stroke outcomes. Wrist flexion, radio-ulnar pronation and humeral internal rotation are identified as major contributors to speed of serve (Tanabe & Ito, 2007). Elbow extension and wrist flexion also appeared to be the major contributors to generation of racquet speed (Gordon & Dapena, 2006).
    REFERENCES:
    Tanabe & Ito (2007) A three-dimensional analysis of the contributions of upper limb joint movements to horizontal racket head velocity at ball impact during tennis serving Sports Biomechanics Sept 2007; 6(3): 418-433
    Gordon & Dapena (2006) Contributions of joint rotations to racquet speed in the tennis serve Journal of Sports Sciences Jan 2006; 24(1): 31-49
    Acknowledgement
    This work is supported by Science Foundation Ireland under grant 07/CE/I1147.
    This work is supported by the Tyndall National Institute under NAP Grant 209.
     
  30. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

    Joined:
    Feb 25, 2006
    Messages:
    11,055
    Location:
    Stuck in the Matrix somewhere in Santa Clara CA
    You are considering only one case for the double pendulum model. You can construct a model where the the hand velocity is zero, positive or even negative (moves backward after contact). It depends on the relative masses (of the hand/arm and racket) involved.

    http://www.tutelman.com/golf/swing/golfSwingPhysics2.php

    [​IMG][​IMG]

    Note that a player's arm is typically 5 to 6x the mass of a tennis racket (whereas the racket is typically 5 to 6x the mass of the ball). Here's an interesting article about the most efficient tennis racquet:

    http://www.racquetsportsindustry.com/articles/2004/10/the_worlds_most_efficient_tenn.html
    .
     
    Last edited: May 8, 2012
  31. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Interesting from what SA provided above-


    With professional long-drive golfers, the shaft length is longer (up to 50 inches), the natural swing time is much longer, and a swing with a natural release is anatomically impossible. Professional long drivers must use positive wrist torque (forcing the club out) to complete the swing.

    The normal golf swing does not require positive or negative wrist torque during the second phase of the downswing; therefore the hands are passive, and the golf stroke can be more accurate with fewer muscles involved.
     
  32. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    Trying to find interesting points for coaching

    The interesting quote from http://www.racquetsportsindustry.com...ient_tenn.html is:
    --->
    I analyzed a high-speed, slow-motion video of a top college player serving at top speed. Just before impact his racquet reaches top speed and his forearm slows down. The forearm slows down just before impact but it doesn’t come to a complete stop before impact.
     
    Last edited: May 9, 2012
  33. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    I expect this is something most of the instructors here knew; where is the quote from?
     
  34. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Want to share some of those hidden gems you found?
     
  35. chico9166

    chico9166 Guest

    And I think if he did try and stop a segment "cold", he would end up in a sling. I don't think it's anatomically possible without injury. The body won't stand for it.
     
    Last edited by a moderator: May 9, 2012
  36. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    IN the summary from the SA provided golf site-

    Toly might be interested-

    Do not apply wrist torque to swing the club out or forward into the ball. You may think you are increasing the clubhead speed with "hand action", but the physics shows that it does exactly the opposite.

    When you’re practicing at the range, practice by first swinging the club about your shoulders as though you are going to throw the club – don’t use your hands:
     
  37. toly

    toly Hall of Fame

    Joined:
    Sep 2, 2010
    Messages:
    1,993
    In professional tennis just before impact forearm doesn’t slow down.

    See please picture below from post http://tt.tennis-warehouse.com/showthread.php?t=361610

    [​IMG]
     
  38. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    The quote/observation is from Rod Cross

    1.The quote is from
    http://www.racquetsportsindustry.com...ient_tenn.html
    (Rod Cross)

    2.As you see from #137 "MOST" of your sentence above is overstatement of the day

    3.Please see that the quote ABOVE is about serve,NOT FOREHAND

    4.I went to see articles by Brian Gordon about SERVE(not forehand) at tennisplayer.net
    He has some drawing based, I believe, on OBSERVATIONS of college players (please note the word OBSERVATIONS).
    The drawings do show:
    a) the velocity of the RACKET increases till the contact (please note the word RACKET).

    b)the acceleration of the RACKET DECREASES AT SOME MOMENT before the contact but NEXT gets bigger JUST before the contact

    I cannot provide links/URLs to tennisplayer.net.
    The title of the article is "The 3D Serve:Upward Swing Part 2"
    The computer interface provides numerical data of acceleration of the RACKET
    I have clicked the icon described as "Racket Speed Data"

    As of now I cannot find corresponding data for FOREHAND at tennisplayer.net
     
    Last edited: May 9, 2012
  39. toly

    toly Hall of Fame

    Joined:
    Sep 2, 2010
    Messages:
    1,993
    Where did you find that actions of the hands decrease club head speed?:shock:
     
  40. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    As I stated,
    on the site SA provided in the summary if I remember right.
     
    Last edited: May 9, 2012
  41. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    How you figure?
     
  42. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    Is Toly representative of most coaches? Is he a coach?
    I though he was a math guy who loves tennis.

    and what is this about velocity incr, but accel decr,
    all prior to contact.
    So the accel is less, but still happening?
     
  43. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    Your second question

    Your second question-see the sentence below
    --->
    b)the acceleration of the RACKET DECREASES AT SOME MOMENT before the contact but NEXT gets bigger JUST before the contact
    --->
    Once more:
    1.Those data are of Brian Gordon
    2.It is NOT very easy to see what is the time scale of what is happening
    3.It is about the RACKET
    I cannot quote anything about the ARM

    4.THE quote about Brian Gordon is about SERVE,NOT FOREHAND
    OP was about FOREHAND

    5.I do NOT know whether players can control BOTH speed and acceleration of the RACKET at the same time
    You can hang me on a coconut tree because I do NOT know

    6.I used to believe that controlling BOTH speed and acceleration of the racket is easier using the HEAD HEAVY RACKET
    but the issue is kind of moot because all my students use head LIGHT rackets

    7.I do NOT know what are OBSERVATIONAL DATA for PROFESSIONAL TENNIS PLAYERS
    where the word PROFESSIONAL is meant is an OPPOSITE of COLLEGE PLAYERS (observed by Brian Gordon)
    8.Brian Gordon has three curves for three components of the speed of the racket VECTOR:
    lateral -red
    forward-green
    vertical-blue
    9.If we want to see/discuss forehand probably seeing three separate components would help to understand biomechanics here
     
    Last edited: May 9, 2012
  44. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    LOL,
    I'm just trying to find out what the point of the post is. Slowing of a section as the next speeds up and energy transfers is how the kinetic chain is demonstrated to work, right?

    I don't think we can know or control a speed, but you can seek to control the acceleration to a point.
     
  45. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    Kinetic chain will be addressed

    Kinetic chain will be addressed
    You had a chance to hang me on a coconut tree when I was in South Carolina
    this year.You missed your chance,pal.
     
  46. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    there is always next time, lol.
     
  47. julian

    julian Hall of Fame

    Joined:
    Dec 20, 2006
    Messages:
    3,247
    Location:
    Bedford,Massachusetts,US
    I expanded post #143

    I expanded post #143
     
  48. toly

    toly Hall of Fame

    Joined:
    Sep 2, 2010
    Messages:
    1,993
    In Federer FH, I don’t see any slowdown in the arm/forearm before impact.

    [​IMG]

    The red digits show variation of the end of the arm/forearm (wrist) speed in percents to the maximal speed. The green racquet demonstrates its position around/during impact.

    The wrist moves forward with different, but positive acceleration!!! So, double or triple pendulum model is completely useless for tennis FH description. IMO, it is misleading math model.

    Btw, Federer’s FH picture has very good correlation with next picture (taken from SystemicAnomaly post #11). It seems that serious physicist did very good job.:)

    [​IMG]
     
    Last edited: May 9, 2012
  49. 5263

    5263 G.O.A.T.

    Joined:
    Mar 31, 2008
    Messages:
    10,409
    But his quote was about the serve.
     
  50. toly

    toly Hall of Fame

    Joined:
    Sep 2, 2010
    Messages:
    1,993
    Did you see the post #137?
    In case of the serve there is no way we can use double-triple pendulum model, because gravity works in opposite direction to the swing path.
     
    Last edited: May 9, 2012

Share This Page