Serving Kinetic Chain

Discussion in 'Tennis Tips/Instruction' started by BU-Tennis, Jan 10, 2009.

  1. BU-Tennis

    BU-Tennis Semi-Pro

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    Ok. So i was watching some slow motion video of pro serves. And the biggest thing that I noticed was how the so called "kinetic chain" is almost non existent. I was under the impression, and have told many people, that in order to serve well you have to fire the legs, hips, shoulders, arm, then wrist. However, I noticed that after the legs start to explode into the shot, the arm, torso, hips, and shoulders move at the same time. Check out the video below to see what I mean. While the kinetic chain sounds good I think it is nearly impossible to accomplish correctly. Not to mention, anytime I try it, my arm feels like its going to rip off. I think its important to notice how the body moves and rotates to add power and consistency to a serve but we can't forget that you still have to swing the racquet with the arm also.

    http://www.youtube.com/watch?v=WWC1hcKBh4g&feature=related
     
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  2. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    Not true. The kinetic chain most certainly does exist, and is very important, for an efficient, effective service motion. It seems that your understanding of the kinetic chain principle is flawed.

    The chain consists of a sequence or pattern of overlapping links. This concept is also known as the kinetic-link principle or the linked system of transferring forces. A simple chain may consist of a simple series of overlapping actions -- a single action occurring & then concluding as another one starts up. We sometimes think of a kinetic chain in tennis as a sequence of events happening from the ground up.

    However, the serve, as many other chains in tennis, are a bit more complex than this -- it is not a single simple chain of events. A number of actions occur in a complex pattern of parallell and sequential events.

    Let's look at just a few segments of the service motion. Note that the legs are bending as the ball is tossed. The legs subsequently extend as the racket (head) drops behind the back. The legs should be fully extended (or nearly fully extended) as the arm and racket start their extension -- the upward swing of the racket head upr to contact the ball.

    USTA Player Development - Technique: The Kinetic Chain

    .
     
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  3. BU-Tennis

    BU-Tennis Semi-Pro

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    I didn't say that the kinetic chain didn't exist. Just that it is a little more simple in execution than what was previously thought. It is mainly a subconscious motion. And i was mainly talking about the body involvement. the usta says the kinetic chain is the leg drive, torso rotation, upper arm elevation, forearm extension, and hand flexion. Some people add that the hips should fire before the shoulder. I mainly suggest that the torso and arms start moving at the same time, with the arm actually moving at a faster speed. When the rotation is complete the legs are fully extended, the chest is mostly open to the net, the upper arm is elevated, with the final part of the chain starting to occur. The new kinetic chain should merge trunk rotation and upper arm elevation into one movement, try to rotate your body without moving your arm, its impossible. People, like myself, who don't have access to high quality coaches and fancy facilities are left to discover tennis by themselves, and with the USTA and other people giving out advice that is too technically advanced for anyone to actually incorporate into their game is potentially hazardous. The kinetic chain, while it happens, is a natural development in the service motion and should not be forcibly incorporated.
     
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  4. WildVolley

    WildVolley Legend

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    I too am a little confused by your post.

    The first thing people are taught when learning the serve isn't the kinetic chain. I find it best to start with the proper grip and contact point and then work from there. I start beginners with a very short swing from the racket drop position and only later incorporate a full swing and the rest of the body.

    I think the kinetic chain is a concept. The serve is a complex compound movement. How to maximize serve efficiency is a really a combination of art and science at this part. High speed video and computer modeling is giving us a better idea of how the best servers do what they do.

    I think you can help train yourself using a video camera and slow motion video of good players. On the other hand, a good coach can help you recognize things that you are doing or not doing.

    Almost all high level tennis occurs at a subconscious level with respect to stroke production, but that only develops out of a lot of conscious adjustments and repetition.
     
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  5. BU-Tennis

    BU-Tennis Semi-Pro

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    I didn't say that the kinetic chain is the first thing taught. But when someone asks in a forum how to improve their serving technique the kinetic chain concept is usually one of the ideas presented.

    Also, the main idea of the post is that the kinetic chain is flawed in its application. Although the body does move in this complex pattern, it is not a conscious effort by the player and never was even when first learning. To try and consciously coordinate these complex movements can result in poor form and injury.

    I wanted to call attention to the fact that the arm starts its movement at the same time as the body and not just in a passive form. The arm must move into position at the same time as the body is rotating. Then, once they are in the hitting position, the elbow can straighten, the forearm can pronate, and the ball struck.
     
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  6. pierretennis

    pierretennis New User

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    BU- In France we realize that the serve is made up of rotations and linear movements. In America, they look purely at rotations, no? Maybe that is the flaw?

    Pierre
     
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  7. BU-Tennis

    BU-Tennis Semi-Pro

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    That is a good point pierre. I think the rotation of the body is sometimes deemed more important than the actual vertical movement of the arm. This could be the reason we see people over-rotating on their serve and losing balance and with virtually no pronation in the serving arm, which is created by the recoil of all the energy moving upward.
     
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  8. NamRanger

    NamRanger G.O.A.T.

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    Sometimes players have to consciously recorrect their technique. Even though professional level footwork is subconscious, they had to do thousands upon thousands of hours of training to make their footwork 2nd nature.



    Serving for some people is an ackward and unnatural motion. I have seen plenty of players who are just serving without thinking, and their kinetic chain is completely out of sync. If the do not consciously practice it, it can never become subconsciously done.



    The arm does not move with the body. The arm is moving as a result of the body creating an upward and forward force.
     
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  9. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    I do not agree with this. The kinetic chain of the serve is not simple at all. However, it may not be all that important for a player to understand all the details or intricacies of the kinetic chain. On the other hand, it is probably beneficial for a good coach to understand these details.

    A novice player does not necessarily need to be aware of the term, kinetic chain, at all. However, as a player develops and refines his/her strokes, it may be important to become aware of some of the details.


    As a first order approximation, it might very well be useful to think of some of these elements happening at the same time. However, if flaws exist because of this notion, it may become necessary to refine these ideas. For instance, the arm and torso do not really move together (at least not all of the time). At the racket head drops and the torso is rotating (back toward the net), the torso actually leads the elbow & arm -- the elbow/arm lags behind a bit which results in a pectoral stretch. When this pectoral stretch is released, the arm starts to accelerate faster than the torso rotation.

    The USTA (& others) is not forcing the concept of the kinetic chain down anyone's throat. It is presented for those who are ready to hear about it. Some players will benefit from knowing about the details while others will not. One must learn how to crawl and then walk before running. It is true that a good coach should not overwhelm the novice player with advice that is too technically advanced. That advice is meant players who already know much of the basics and are probably ready to learn more about the details.
     
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  10. HuusHould

    HuusHould New User

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    physics of the kinetic chain

    I think this is an important point, the guidelines are probably directed at coaches who are to decide how to best convey the information to their students.

    I can understand where the OP is coming from though. I guess what he's saying is that there is a much bigger overlap in the segments of the chain than expected (to the point where they seem to be happening simultaneously). I personally have found it easier to just try to mimic a professional utilising pause house (Sam Groth) than try to understand the physics behind the whole thing and incorporate it into my natural swing. But of course trying to imitate a professional can be hazardous because you get it wrong and that's where a teaching pro who understands the principles behind what's happening can be handy.

    I also agree with what someone else said that optimal utilisation of the kinetic chain might come naturally to some players, but not to others.

    You seem to know what you are talking about Systemic Anomaly. I've been searching these threads in a bid to find an explanation of the physics behind the kinetic chain with reference to the serve. I know it's probably simple, but I've never understood the "transfer of force" from one segment to another. One guy in another thread described it as a sequence of pulleys where the larger pulleys are activated first……….does this make sense, can anyone explain it in layman's terms. Cheers
     
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  11. Chas Tennis

    Chas Tennis Hall of Fame

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    Limitation of the Kinetic Chain Concept

    Suppose that muscles were stretched and then all parts of the body were brought to a complete stop for 2 tenths of a second. Then the pre-stretched muscles were allowed to shorten and, say, move the arm? How does the Kinetic Chain concept deal with the above motions involving a complete stop and pre-stretched muscles? The Kinetic Chain concept deals with a sequence of increasingly faster moving body parts. How can the KC concept interpret the above motion in terms of speeding up body parts since the body was brought to a complete stop? The KC concept falls apart for the pre-stretched muscles that are not in a simple sequence.

    The internal shoulder rotator muscles used for the serve are pre-stretched and could conceiveably be used with a delay. For example, say the legs thrust up and then the body stopped moving completely. Then two tenths of a second later the upper arm was released to rotate (internal shoulder rotation).

    The first researchers who realized that internal shoulder rotation powered by pre-stretched muscles were contributing significantly to racket head speed on the serve also realized the implications to the Kinetic Chain view. They stated so in their early publications in the 1990s. Of course, this KC issue also applies to baseball pitching, badminton smashing, volleyball spiking and many other sports motions, possibly all. The pre-stretched muscles may also act in a quick sequence of body parts, with negligible delays, that appear to be steadily speeding up and seem to be a simple Kinetic Chain of larger and slower body parts speeding up smaller ones finally ending with the hand or foot.

    http://www.researchgate.net/publica...nk_in_proximal-to-distal_segmental_sequencing

    "Long-axis rotation: the missing link in proximal-to-distal segmental sequencing.

    Robert N. Marshall
    Bruce C Elliott

    Department of Sport and Exercise Science, The University of Auckland, New Zealand.
    Journal of Sports Sciences (Impact Factor: 2.1). 05/2000; 18(4):247-54. DOI: 10.1080/026404100364983
    Source: PubMed

    ABSTRACT Most assessments of segmental sequencing in throwing, striking or kicking have indicated a proximal-to-distal sequencing of end-point linear speeds, joint angular velocities, segment angular velocities and resultant joint moments. However, the role of long-axis rotations has not been adequately quantified and located in the proximal-to-distal sequence. The timing and importance of upper arm internal-external rotation and pronation-supination in the development of racquet head speed have been examined in the tennis serve and squash forehand drive and considered in relation to conventional concepts of proximal-to-distal sequencing. Both long-axis rotations reached their peak angular speeds late in both strokes, typically after shoulder flexion-extension, shoulder abduction-adduction and elbow extension. These results clarify and confirm the importance of upper limb long-axis rotations in the production of racquet head speed. It appears that traditional proximal-to-distal sequencing concepts are inadequate to describe accurately the complexity of the tennis serve or squash forehand drive. It is essential to consider upper arm and forearm longitudinal axis rotations in explaining the mechanics of these movements and in developing coaching emphases, strength training schedules and injury prevention programmes."

    The Waiter's Tray serve does not use much internal shoulder rotation so its use of pre-stretched muscles appears like a classic Kinetic Chain of increasing speed for the next body part.
     
    Last edited: Apr 20, 2015
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  12. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    ^ Not quite following all of this Chas. The Abstract is particularly difficult to follow. Perhaps you could translate it into English for us.

    When the legs extend (thrust upward), is this not facilitating the racket drop and the stretch in the shoulder (ESR)? Isn't that slight delay inherent in the stretch-shortening cycle? Or is that your point? In a thread from last year, you talked about disregarding the kinetic chain wrt to tennis serve. Is that still your stance? While the KC principle might not fully explain everything that is happening in the serve, it does not mean that is should be tossed out as irrelevant. The 1st 2 links below, indicate that there are 2 underlying principles involved: the SSC of the muscles and the kinetic chain.

    https://biomechanics101.wordpress.com/2013/07/09/tennis-anyone/
    http://www.usta.com/Improve-Your-Game/Sport-Science/114390_Technique_The_Kinetic_Chain/

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/
    .
     
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  13. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    Don't think that I'm up to the task on this. The kinetic chain is usually presented as something of a simplification of the sequence that happens for the serve and other strokes. The sequence is a series of overlapping links (or segments). However the gory details on how the energy or forces are transferred from one link to the next is something of which I have only a superficial grasp. Perhaps someone with more in-depth knowledge of anatomy, biomechanics and physics could give you a better answer.

    I find it useful to sometimes regard the actions of certain segments as stretching and releasing elastic bands. I also find it useful, at times to refer to gears for the transfer from one segment to the next. Pulleys might serve to understand the action of muscles and connective tissues (tendons, ligaments, fascia). However, we might consider levers for the action of bones and joints. Our brain and nerves might be regarded as a CPU -- this is needed to coordinate and optimize the timing of the various elements in the chain. Proprioception is a large part of this.

    http://www.cheshirefitnesszone.com/blog/understanding-the-kinetic-chain-for-better-performance-and-fewer-injuries/
     
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  14. julian

    julian Hall of Fame

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    Mr. SystemicAnomaly is too modest-kudos

    Mr. SystemicAnomaly is too modest
    He understands the paper
    http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/49. TennisDPend.pdf
    The paper describes a kinetic chain consisting of two pieces.
    I am deadly serious
    Julian
     
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  15. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    ^ The mental clarity is not what it once was. More lucid some times than at other times -- brain fog right now. Perhaps mood and visual fatigue is part of it. Had forgotten all about the pendulum stuff. As I recall the double pendulum is an approximation for part of the serve. I had also talked about the trebuchet and the triple pendulum.
    .
     
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  16. shindemac

    shindemac Hall of Fame

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    Kinetic chain in layman's terms can be expressed plainly and understood easier by beginner. Unfortunately, the analogies of using gears and pulleys don't accurately reflect what is happening in real life, even though it may help some grasp the concepts. I express the concepts of kinetic chain all the time for serve, but I don't use those terms because some may not know what it means or only have a superficial understanding.

    Instead of bad analogies, the best way to understand how it works is to learn how to throw. Throwing is all about the kinetic chain and removes some of the difficulties of serving like having a good toss and the awkward body contortions needed for trophy pose. Having a good trophy pose doesn't necessarily translate to more power. Having a good kinetic chain will. Most beginners who try really hard to have a good trophy pose have really bad kinetic chains, so they end up arming the serve. So no hitches and having smoothness is important. Also, timing is important. For pitchers, they only rotate their trunk (hips or torso) after their foot has landed. It's as simple as that. If you rotate before, you are rotating too early which is most beginners end up doing. Why, I can't tell you, but that's all you need to know to get a good serve.

    Best way to develop kinetic chain is to learn how to throw. Videotape yourself. iPhone has frame by frame feature so you can check if you are rotating too early. Also, easy to check for balance and things like that. Your ability to throw is highly correlated to your serving speed.
     
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  17. Chas Tennis

    Chas Tennis Hall of Fame

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    My interpretation. I don't know anything about the "squash forehand drive" and have ignored comments I think refer to it.

    ABSTRACT Most assessments of segmental sequencing_sequence of body part motions, from one to the next, usually from bigger, slower body parts, core or legs, to smaller, faster body parts such as the hand_ in throwing, striking or kicking have indicated a proximal-to-distal _ proximal means core and maybe legs also in usage_distal means more 'away from' with the hand being the most distal_ sequencing of end-point linear speeds, joint angular velocities, segment angular velocities and resultant joint moments. _The Kinetic Chain Concept deals with increasing speeds of segments or body parts_ However, the role of long-axis rotations _internal shoulder rotation of the upper arm and pronation of the forearm_ has not been adequately quantified and located in the proximal-to-distal sequence. _Speculating, Bruce Elliott may have viewed the serve as a Kinetic Chain during his early tennis stroke research in the 1980s and realized that his new results included an important new contribution to racket head speed - internal shoulder rotation - not described by the Kinetic Chain Concept._ The timing and importance of upper arm internal-external rotation and pronation-supination in the development of racquet head speed have been examined in the tennis serve and squash forehand drive and considered in relation to conventional concepts of proximal-to-distal sequencing. Both long-axis rotations reached their peak angular speeds late_there is a delay between pre-stretching muscles and using them for internal shoulder rotation_ in both strokes, typically after shoulder flexion-extension, shoulder abduction-adduction and elbow extension._Speed of body parts develops in the serve, as the Kinetic Chain might indicate, but there is in addition a second significant contributor, ISR, that is not developed by increasing speed but separately as energy stored in pre-stretched muscles. Elliott et al called it "the missing link"._These results clarify and confirm the importance of upper limb long-axis rotations_internal shoulder rotation_ in the production of racquet head speed. It appears that traditional proximal-to-distal sequencing concepts _the Kinetic Chain Concept_are inadequate to describe accurately the complexity of the tennis serve or squash forehand drive. It is essential to consider upper arm and forearm longitudinal axis rotations_internal shoulder rotation and pronation_ in explaining the mechanics of these movements and in developing coaching emphases_ for highest performance observe and optimize internal shoulder rotation and pronation_, strength training schedules and injury prevention programmes."

    The Kinetic Chain Concept, as I interpretation it, has a body part passing on its speed to the next body part, then to the next, etc.

    To illustrate problems with the Kinetic Chain Concept, I made up a simplified example (one isolated part of the serve) that consists of the leg thrust and pre-stretching of the shoulder's ISR muscles, the lat and pec. Later, after a delay time, these muscles could be used for ISR, as is done in the serve.

    1) The legs are not next to the shoulder. How does the Kinetic Chain Concept handle body parts that are not next to one another but separated by other body parts?

    2) By thrusting, the legs do not create higher speeds in any part of the shoulder. When you consider the body to jump, peak and then stop, the shoulder is motionless. How does the Kinetic Chain Concept handle this motion when speed has not been increased?

    3) What the leg thrust does is to pre-stretch muscles. How does the Kinetic Chain Concept handle pre-stretched muscles, especially ones where there is a considerable time delay between stretching and triggering to shorten?
     
    Last edited: Apr 23, 2015
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  18. sureshs

    sureshs Bionic Poster

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  19. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    Not sure that I understand your 1st sentence. Did you mean actually mean "understood easily by beginners"?

    Using ideas like levers, pulleys, gears and the like could help to understand some elements of stroke mechanics or parts of the kinetic chain. However, using these ideas to completely describe a full kinetic chain is probably not useful for most tennis students as you appear to be saying. It is, nonetheless, not uncommon to refer to levers, pulleys, et cetera when teaching anatomy or kinesology:

    https://quizlet.com/21076057/kinesiology-test-2-flash-cards/
     
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  20. julian

    julian Hall of Fame

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    I do not understand your post

    I do not understand your post.
    "Two pieces" were referring to the kinetic chain.
    "Two pieces" were NOT referring to the paper
     
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  21. SystemicAnomaly

    SystemicAnomaly G.O.A.T.

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    ^ sureshs humor, I assume.


    .
     
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  22. julian

    julian Hall of Fame

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    Your question number two is flawed

    Two facts below do not contradict each other:
    1.shoulder are motionless till some moment
    2.there is a transfer of energy from legs to shoulders.
    The part of the explanation is that shoulders can be kept semi-rigid till some moment by some muscles.
    Please try to think about it
     
    Last edited: Apr 23, 2015
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  23. sureshs

    sureshs Bionic Poster

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    Julian understands humor only if it is the form of equations. But yeah it was a bad joke.
     
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  24. Chas Tennis

    Chas Tennis Hall of Fame

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    I don't have a clear idea of your point. Please explain.

    Do you see the hitting shoulder as a link in a kinetic chain that has increased speed at the peak of the jump?

    At the highest point of the jump, I see the shoulder as having zero speed and as a wound-up spring. Energy originated from the leg thrust. How does the Kinetic Chain work with zero kinetic energy in speed and potential energy in a wound up spring?

    Besides, I'm not experienced applying the Kinetic Chain Concept and don't believe in it. Until someone can show in very clear terms how KC can describe how the leg thrust can produce internal shoulder rotation, after a delay of tenths of a second, the Kinetic Chain Concept does not seem creditable.

    I've have read the following early books for discussions of the Kinetic Chain.

    High Tech Tennis, 2nd ed by J. Groppel

    and the very early, often referenced, book
    Scientific Principles of Coaching 2nd Ed, J. Bunn

    I have not read many recent references.
     
    Last edited: Apr 23, 2015
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  25. julian

    julian Hall of Fame

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    The first reaction

    Your quote
    "Besides, I'm not experienced applying the Kinetic Chain Concept and don't believe in it."
    My first reaction is:
    I would advise to get in touch with John Yandell or Brian Gordon on this subject.
     
    Last edited: Apr 23, 2015
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  26. julian

    julian Hall of Fame

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    Preservation of momentum

    The Kinetic Chain is based on the preservation of momentum.
    A trunk is an element which transfers momentum from legs to shoulder
    Please read the introductory part of
    http://www.udel.edu/PT/PT Clinical Services/journalclub/sojc/01_02/may02/mcmullen.pdf
     
    Last edited: Apr 23, 2015
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  27. julian

    julian Hall of Fame

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    Please read

    Please read
    https://books.google.com/books?id=8...6AEwAA#v=onepage&q=Kinetic Chain Bunn&f=false
    Closed Kinetic Chain Exercise: A Comprehensive Guide to Multiple Joint Exercise
    By Todd S. Ellenbecker, George J. Davies

    PS
    54 percents of power/speed of serve comes from legs and trunk.
    See the paper by Kibbler 1994
    If you do NOT believe in Kinetic Chain this 54 percents is "lost" somehow
    ----->
    There are many examples of kinetic chain breakage in tennis players. For example:
    • If the knees are not bent more than 10 degrees in the serve cocking phase, it
    places a 23% greater load on the shoulder and 27% greater load on the elbow to
    achieve the same serve velocity.
    • If the hips don’t counter rotate and then rotate into the serve, it requires 28% more
    load in the elbow to achieve the same ball velocity.
    • If the trunk does not rotate to provide force to the shoulder, it requires a 34%
    increase in shoulder velocity to achieve the same ball velocity.
    • The motion that helps to protect the elbow against the loads in the serve is
    generated by the long axis rotation of the arm and shoulder rotation. If long axis
    rotation is not present, the forearm muscles would have to be 60% larger in size
    than they are to protect the elbow against injury, either on the medial (inside) or
    lateral (outside) areas.
     
    Last edited: Apr 23, 2015
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  28. shindemac

    shindemac Hall of Fame

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    No, I meant easier. I doubt many who are new to tennis or these forums know what you mean by kinetic chain or how to achieve a better kinetic chain. Therefore, I never use these terms when giving advice to beginners (or when just giving advice). But it's still important to express these concepts and be able to tell someone to achieve a better kinetic chain, which I do wo using the words 'kinetic chain'. Hence I use simple words that still get the same point across.

    The concept of pulley and gears is helpful, but some will misinterpret how to achieve a better kinetic chain if they follow it literally. For pulleys and gears, there is no delay when one gear turns and the next gear moves immediately. Both parts move at the same time. But in the serve and in pitching, there is a delay. Like I said in the pitching example, the pitcher must not rotate his trunk (or hips) before his foot lands on the ground.
     
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  29. julian

    julian Hall of Fame

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    Kinetic Chain

    Do you believe in the Kinetic Chain for one of the following sports:
    Golf,baseball,football,skating,the FLOP high jump?
     
    #29
  30. HuusHould

    HuusHould New User

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    The gear analogy is an interesting one, so it's like you are coiling initially in a low gear, then you go higher at the end of the coil/start of the uncoil after you've built up momentum, then you use a lower gear for maximum speed at the end.

    What do you guys think of this clip. I think they're flogging some sort of hip strengthener, but what is said seems to make sense;

    https://www.youtube.com/watch?v=pLf_MJXzBVg
     
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  31. Chas Tennis

    Chas Tennis Hall of Fame

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    I don't agree with the Somax view of the serve biomechanics. I have posted on the issue here more than once. But using TW searches and Google searches I did not find the main posts. The helicopter view particularly did not seem correct to me.
     
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  32. julian

    julian Hall of Fame

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    Google

    Google tennis-warehouse chastennis somax
    provides th link (no space between chas and tennis)
     
    #32
  33. HuusHould

    HuusHould New User

    Joined:
    Apr 12, 2015
    Messages:
    6

    Yeah I agree the propellor analogy is not quite right, you don't swing your arm around horizontally to hit a tennis serve!

    But he makes a good point, that the more you can coil your segments away form the ball, the more time there is to build up angular velocity at the joints in question.
     
    #33
  34. 2ndServe

    2ndServe Professional

    Joined:
    Mar 6, 2008
    Messages:
    981
    There are certain elements a player must have but I find the serve is very idiosyncratic. There are players with like warinka who looks like he has no leg drive yet he serves bombs, some have a very high toss and some a very low toss. I think it highly dependent on how you sync both arms on the takeaway.

    Each player does it differently but after 100,000 repitiitions they make minute changes and they can make it work even with flawed mechanics.

    I've seen them all and the ball doesn't care wear the racket head speed comes from, some propel with the legs some have great rotation, others have perfect timing, others strong wrist pronation, some blessed with long arm levers. The good ones have great racket head speed, swing up and produce a lot spin.

    I would work on the toss, it controls how efficient the kinetic chain is, guys like Fed and Feliciano have such nice tosses everything flows without a stop or pause in the kinectic chain.
     
    #34

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