Discussion in 'Tennis Tips/Instruction' started by albesca, Dec 31, 2011.
Yes Toly, i'm watched along L&R forehand video and I have come to your own conclusions !!
Thank you Dellon for ur contribution.
You would upload ur photo up on a image storage service.. after the uploading, get the pic link and insert it with the pic button in post editor.
I like "Google Photos - Picasa Web Albums" but if you search "image hosting" on google .. you can find thousands other for free.
How does the arm and wrist being active negate the assertion that the power is coming not from the arm but from the legs and core? The arm is of course active because it's ultimately the thing that is being whipped by the legs and the body. And again, the fact that the arm is whipped into the ball doesn't mean that the muscles in the arm aren't being used. They most definitely are being used, but more like a spring.
Also you do realize that the Lock and Roll guy is a pretty accomplished player and coach? I've personally found his videos to be very helpful.
Just go grab a tennis racquet and a ball, go out to your favorite wall, and hit a few. Serves, ground strokes and overheads all work on the principle that larger muscles groups unload energy into whipping the racquet into the ball. Actually most sports that involve throwing and hitting things use this concept. Just throw a ball - same idea. Your legs and core whip your arm around to throw.
The harder we compress the ball, the more it will bounce out, if you do not comprehend this, and show scientific data disagree with me, I quit.
Sure, but the mass behind it as 10 time larger. result in the ball speed will be more.
Think, Toly, think.
The racquet can really hurt a tennis ball and not just it. See for example Youzhny, PhD scientific experiment http://www.youtube.com/watch?v=fi-CgSO9Evw&ob=av3e around 0:40.
Kid experiment in video (not scientific?), http://www.youtube.com/watch?v=ym3wczI0s84, shows that ball bounce high is not directly proportional drop high. The physic low is: The greater the height of the incident ball, the less the efficiency rebound (more damage).
About this matter, see please my posts http://tt.tennis-warehouse.com/showthread.php?p=5895380#post5895380 and http://tt.tennis-warehouse.com/showthread.php?p=5892760#post5892760.
I'm not here to prove anything to anyone. I say only that for years I left the control of my forehand to the trunk and legs ..and I'm still waiting yet to see a decent ball come out from my strings (a bit of spin and a bit of speed.. don't pretend so much).
Only when I moved my attention to the speed of the arm in the forward swing the level of my forehand has changed, that doesn't mean i don't use legs and trunk .. only i don't think at them, I know my lower body is loaded and that's all, so I cannot do other then to conclude that the arm is crucial in the production of ball speed ... crucial.. and the matter the arm go fast.. are we! Kinetic chain does anything by itself. The lines attached in the monkey drum don't impact a mass .. we need to do it, that changes everything .. dragging the arm like a monkey drum is not enough and the nice R&L guy would spend some words in why and what he does with his arm too.. because, by me, it isn't secondary.
But mine is only very modest opinion of a tennis fan, so take it for what it is.
What the heck are you guys arguing about?
Just keep it simple. Use your arm, relaxed, and whip the ball hard. Get your body involved and your legs help with the body turning so the arm can swing a larger range/path.
Using your arm only will give you a very short range and you will cramp the muscles together. That's all.
Don't really know exactly what Brian Elliot means by this 15% contribution. However, what I've read of his published study, he seems to indicate that a full well-coordinated kinetic chain is important to high level tennis strokes. In light of this, the 15% figure appears to be rather misleading. It suggests to some that the contributions from the legs, hips, core and trunk are not all that important. I do not believe that this is the case. maxpotapov's statements above could have some merit.
If the contributions from the links are really not all that important, then why do high level players "waste a lot of energy" employing those links on most of their shots? Often, they are playing or practicing for 3-5 hours or more a day. It would seem foolish for them to "waste energy" for an extended period of time if the returns are trivial or unimportant.
It is my belief that using the legs, hips, torso, etc reduces stress to the shoulder and rotator groups. We transfer "energy" to the shoulder and arm from the previous links rather than have the shoulder (and arm) generate it all own its own. The leg muscles are much stronger that the shoulder and arm muscles. The legs, hips and torso also represent larger masses (with greater rotational inertia) than the shoulder/arm and racket. So when we transfer the energy from those larger parts to the shoulder, it allows the arms to accelerate more easily (with less stress).
I am keenly aware of the stresses in my own shoulder. For the past few years I've had somewhat limited shoulder function (from an old volleyball injury to the rotator groups -- some 20 yrs ago). If I prepare late for a shot and try to rely solely on my shoulder/rotators to swing my racket, I experience significant pain. However, when I employ my legs, hips and torso, I can get my shoulder/arm moving quite fast without pain.
IMO, maxpotapov is 100% correct. The work done by the legs and torso loads up the muscles of the lagging arm/shoulder, and this energy is released when the arm fires. I believe there are studies that show that stretched muscles are able to generate more force/speed when they contract. Ergo, factoring the legs/body out of the equation will have a big impact on the final power delivered.
Of course, the arm muscles are very active. My contention is that the more we are able to let the arm relax by using the legs/body, the more control we will get. If the arm muscles are 100% active, yeah, there will be enough power to launch the ball to the moon, but control will go down the toilet.
Also, IMO, there are many ways to hit the forehand (or backhand). This variation may be due to stylistic preferences, and/or game situations. Thus I would say that it is not realistic to assume that a particular muscle group always contributes a fixed percentage of power for a specific stroke such as the forehand.
One clarification on my point of view - when I say that legs and bodies should be used to the maximum extent, I am not recommending doing upper body rotation that resembles a U-turn! Far from it - in fact, I am not a big believer in UBR. I don't believe that the rotational speed of the upper body is a big contributor to racquet head speed. I don't believe UBR is done for its additive effect to racquet head speed. However, the right amount of upper body turn is essential to properly load/stretch the appropriate muscles. Similar reasoning applies to leg use. Some people, the pros in particular, are able to get a lot out of UBR and legs. Some of us sedentary and stiff types simply will not be able to get as much, but we should aim to maximize what we do get.
Okay, I've said everything I know now, right or wrong...
Wow, this is maybe first time I agree with you. Thanks.
About Bruce Elliot Data - 15%
IMO Elliot is talking about last moment before contact.
It is obvious that we should provide some particular delays for particular actions. Since different parts of the body have a different speed, we want to start from slow body rotation, which would drug passive arm. In this case body contributes 100%. Then we should begin rotating arm around shoulder. Then again some delay, and we start rotating forearm around elbow. The most delay we should provide for the wrist, because it is the fastest joint. During this process, contribution of the body to racquet speed significantly decreases from 100% to 15%. But, this is just my assumption.
Great! What the heck, it's Friday, I'll drink a beer to that!
Again about Bruce Elliot Data - 15%
Let’s assume that when you swing the racquet all parts of the body rotating at maximum speed. In the case of a straight arm the racquet speed can be calculated according to following formula:
Vracquet=Ѡbody x Rbody + Ѡshoulder x Rshoulder + Ѡwrist x Rwrist
Ѡbody = 7 rad/sec; Ѡshoulder = 10 rad/sec; Ѡwrist = 50 rad/sec;
Rbody = 70”; Rshoulder=50”; Rwrist = 25”;
Vracquet = 7/sec x 70” + 10/sec x 50” + 50/sec x 25” = 2240”/sec.
Body contribution is (7/sec x 70”)/ Vracquet x 100% = 22%.
Shoulder joint contribution is (10/sec x 50”)/ Vracquet x 100% = 22%.
Wrist joint contribution = (50/sec x 25”)/ Vracquet x 100% = 56%.
In case of bend elbow FH, the body contribution could be even less. So, it seems that Elliot’s data are correct.
Wrist makes major contribution, 56% feels about right. Simply because if it does not, racquet head would be pulled forward/away because of centrifugal force from those 44%, eliminating angular momentum on the racquet head.
The problem is, if you have not fully developed those 22%+22% on preparation/swing, trying to apply 56% just by wrist... ouch! There's got to be some kinetic energy behind the racquet before you do a wrist flick.
I like that last part, but
how do you get the 1st paragraph?
How would the 44% eliminate angular momentum?
The racket is pulled forward and away to an extent.
My point was, trying to develop angular momentum for the racquet head just by body rotation (passive wrist) is futile because of centrifugal force. On the other hand, trying to develop angular momentum for the racquet head just by wrist (passive body) will hurt your wrist.
If motion is linear, then it's a different story. But I'm talking about circular motion with "wrap around" follow through
IMO centrifugal force is a key to angular mo, so I don't follow that part, but overall I'm mostly with you here.
If swing path is more like a circle, centrifugal force will always pull racquet forward and away from rotational axis (which is spine), fighting the angular momentum I'm trying to develop for racquet head.
That's why it takes extra effort from the wrist/fingers to turn the racquet around, so that it bumps against my left shoulder by inertia (which shows proper angular momentum), instead of pulling my arm forward, following the ball (little or no angular momentum on racquet head).
(When I say "angular momentum", and "swing path" I think about tip of the racquet head.)
Agree. I would not go off topic, but I believe that the improper use of the leg push is involved in the argument we are discussing.
You know many club players (i too..) sometimes copy the pros jumping off the ground and spending a lot of energy without producing relevant raquet head speed. It happens, imho, due the misconception about "the leg push".
We would think at legs continuosly... tennis is played with legs, no doubt about, but there is a particular moment when we have to "don't think about legs" and that moment is, in line with the maxpotapov views, just the forward swing.
Push with legs in syncro with the swinging forward of the arm causes the arm is disturbed, not helped.. and this is what all low level players do... and they do them because it was instilled they have to push with legs to produce power.
We can't control timing of all our leverages and muscles ..we must simply give our nervous system the right reference points to allow the natural coordination... and legs push should start in an instinctive way, and not voluntary, or it starts too early destroying the kinetic chain and wasting a lot of energy.
^ I don't believe that bhupaes was necessarily talking about jumping. Bending the knees and employing a leg drive is used on many groundstrokes where the player does not leave the ground. The kinetic chain starts with a ground reaction force and leg drive which is transferred to hip and trunk rotation.
There is a difference between reality and perception. Even if what you're saying is true (in reality) trying to exercise this sequence "as is" may lead to unwanted results. For example, this sequence can be translated as "push your leg to start the forward swing", which won't do much for your kinetic chain other than hurt your ankle/Achilles...
We operate our body according to our perception, that's why we often have to trick our mind/body into doing the right thing.
^ We really only need to bend the knees on most shots. The ground reaction force and leg drive will usually take care of itself if we bend the knees.
Absolutely Max... and I could understand better if my teacher would explains
using the perceptions i have to feel ..
It's BS, Toly, so many BS that i cannot even analyze to you. Is Mr Elliot date based on superman, some kind of machine that he manufacture or just for all of us, which is human with different strength and weakness ??
You seem like a young kid in a bucket of candy. You pick up these and then you pick up another.
Are you sure you understand what I'm saying ( absolutely no disrespect)
I’m sorry, but our mutual understanding looks really very bad. Can you tell us about your education?
As much as you can go thru University, max post graduate and everything in Nam war 30 years back, you will find me.
Sorry, English is my third language and it certainly doesn’t like me. That’s why I don’t follow your slang in last post and maybe in previous posts too.
Toly, you truly are one of the most delicate tennis players in the world
Thank you Max.
I’ve read in others threads your posts about fingers action. Could you clarify this?
It's about extra leverage from hand/fingers when turning racquet head around the ball. In case of linear motion I can just let go of racquet completely, hence old skool approach of holding the racquet as relaxed as you can without letting it slip out of your hand. But if swing path is more complex/circular with extra action on the ball, I have to fight centrifugal forces that pull racquet head forward/away. And this is where I need any leverage I can get from my fingers to turn racquet head in the desired direction (which is around the ball and across/around my body). With totally relaxed wrist/fingers I would have to work extra hard with my wrist/elbow/shoulder to turn racquet head into desired direction and compensate the pull from centrifugal force.
Yes, I agree.
Something like that I described in posts: http://tt.tennis-warehouse.com/showthread.php?p=5954592#post5954592 and http://tt.tennis-warehouse.com/showthread.php?p=5309329#post5309329
Wow, that's like totally awesome!
You see, great minds think alike
P.S. I will definitely use your research (c) Anatoly Antipin, thank you very much
Thanks SA. What you're saying is exactly my model of how the legs contribute.
So was this thread ever reconciled? Passive arm whipped across body or not?
I like the way @toly answered, so scientific.
. . .
If the ball weight is light as ping pong ball(6-7 grams), hitting with using human arm will be controllable.
But tennis ball weight is around 60 grams, quite heavy, especially when it travelling 80-100 mph, the momentum will be too much that only human arm + 300-400 gram racket can not control the shot well.
. . .
The faster we swing our arm, the more we loss control in it.
So that why we have to use body and leg to help arm generate racket speed.
When our arm swings slower, our hand can control the racket face better.
the arm is dragged by the body initially. then the body rotation stops and the arm is actively whipped through (partly from the stopping but also by using hard muscle contraction).
activating the arm too early is short circuiting the kinematic chain but nobody is using a totally passive arm. a good shot uses all muscles of the body.
At what approximate point would you say the active use of the arm comes in from the beginning of the forward swing to contact point? Maybe halfway through the swing path such that the kinetic rotation of the body is best transferred?
at the very end when the chest is nearly facing the net. biomechanically the best time is when the trunk rotation has reached maximum speed and starts to decelerate.
look at this javelin thrower:
while his body rotates the arm barely moves and while the arm moves the chest barely moves (stopped). high level is to rotate early and separate the arm action from the rotation a lot.
the rotation adds some MPH but the actual shoulder velocites are quite low (under 10 mph). that means the main effect of rotation is not pulling the arm around (although that also plays a role) but to create potential energy and pre stretch the muscles above for their contraction.
Ok thanks that makes sense. But so when the chest is nearly facing the net, you are saying the arm is not to be whipped around passively at this point, but to be actively accelerated using the shoulder muscles, right? Also where exactly on the swing path is the RACQUET when this happens? About half way through the swing path, no?
^^^ also another question, is the wrist kept loose throughout all of this such that it is the only passive appendage in the whole kinetic chain?
Toly, could you explain how one could practically employ arm and wrist to increase racquet head speed? specifically what is upper arm horizontal flexion, internal roatation and how could these be applied to ones game?
I'm not toly but the moves are mainly shoulder flexion and humeral internal rotation. also there is pronation of the forearm and some other micro movements of the wrist.
Internal shoulder rotation is counterclockwise upper arm rotation.
In picture below Serena Williams is trying to hit hard FH winner. Here is original video http://www.youtube.com/watch?v=BJg5cWEviZo.
Her main arm’s motions around contact are:
1. Arm flexion.
2. Internal shoulder rotation.
3. Forearm pronation.
4. Wrist ulnar deviation.
Separate names with a comma.