The arm is not dragging by the body

[rkelley]

Originally Posted by toly

If arm and wrist are being used actively, there is no reason to talk about the whip. In whip, only handle is active and the rest of whip must be passive. IMO, you are using wrong terminology and got me completely confused.

You're looking at this in too much of a black and white fashion. The arm is whipped around. The terminology is correct. Is it completely passive? Of course not. You're taking the analogy too far. You certainly use the arm muscles, but the salient point is that most of the power comes from the legs and the core whipping the arm around, not from the arm muscles contracting without the loading from the legs and core.

[DavaiMarat]

Originally Posted by albesca

Start by saying that this is only the opinion of a tennis lover, I have the pleasure to share that opinion with you.

I think that pushing more with legs or turning fast the trunk will not help on producing more arm speed.

The speed of the arm is produced by the arm.

The important thing is to understand the body posture significantly affects the ability to swing fast the arm.

Searching the perfect distance and taking the perfect posture at a certain time, here is what the body does. During the search for the ball, the positioning of the feet, the body coiling ...the arm doesn't exist. But when it's time to hit the arm becomes the master, and the body simply has to follow his will.

Happy new year to all
Al

Rudimentary physics dictate that one body that is carry by other will inherit it's velocity in addition to any velocity it generates by itself. For example if subway and I run from the from to the back at 15km an hour and the train is moving 60km. I have a velocity of 75 km.

This is the same for rotational acceleration, if my body is turning and my arm is turning as well, the arm will pick up the rotational speed as well as it's own rotation speed, but in this case I believe it's a exponential in gain unlike the linear example I gave you before (w^2). So it's hard to argue that the body doesn't contribute at all let alone not playing a major role in power and rhs.

[albesca]

Originally Posted by rkelley

most of the power comes from the legs and the core whipping the arm around, not from the arm muscles contracting without the loading from the legs and core.

Absolutely agree, the arm do nothing without the loading from the legs and core.

But i still on my idea the trunk doesn't have volountary to drag. It musn't rotate as fast as possible.. legs haven't to work in that way during the forward swing.
The shoulder joint have to move at exactly speed needed by the arm... not less... but not more... because the dragging doesn't add power, but by me, destroy the arm coordination.

[ho]

Originally Posted by toly

It’s true that leg and core rotation provide the major power, but with very low efficiency, from ball/racquet speed point of view. Most of this energy is wasted for rotation of 200 ponds and just a little bit is going to the ball.

As I said, physic law of collision:
m x v = m1 x v1 ( m is mass and v is speed)
1/Ball speed depend on physic law of collision
2/Ball speed depend on how much it is compressed and bounce out by itself and to and advance level, it depends on the prolongation of contact time.
Tell me you comprehend these, ( not disrespect at all, we need to be on the same page) then i continue to the linear energy (whip)

[ho]

Originally Posted by albesca

because the dragging doesn't add power, but by me, destroy the arm coordination.

Drive your car, hit the brake, car stop, you feel like you have an unknown energy push you forward. that energy is Kinetic Energy.

When you drag your arm behind, near contact body rotation slow down, the Kinetic Energy will push your arm forward if you keep a loose arm. Kinetic Energy need time to build up, therefore the idea of dragging emerges as an ingredient in Pull stroke: You pull the racket forward as Nick B. describe in his tape.

[ho]

Originally Posted by DavaiMarat

So it's hard to argue that the body doesn't contribute at all let alone not playing a major role in power and rhs.

The body do contribute to the the speed of your arm. But the main power of your arm is not by itself, but by the fact that body slow down:
Run 25m/h on the train with 50m/h your speed is absolutely 75m/h. Now if the train suddenly stop: You will get kill by your enormous speed instantly.

[toly]

Originally Posted by ho

As I said, physic law of collision:
m x v = m1 x v1 ( m is mass and v is speed)
1/Ball speed depend on physic law of collision
2/Ball speed depend on how much it is compressed and bounce out by itself and to and advance level, it depends on the prolongation of contact time.
Tell me you comprehend these, ( not disrespect at all, we need to be on the same page) then i continue to the linear energy (whip)

I answered on all your claims in post #18, except the idea “… the prolongation of contact time”.
jumpulse.com tried very hard to sell this idea, but without any success. IMO this is nonsense, absurd etc. Even Oscar Wegner quit taking about that.

[toly]

Originally Posted by rkelley

... but the salient point is that most of the power comes from the legs and the core whipping the arm around, not from the arm muscles contracting without the loading from the legs and core.

Your statement contradicts with Bruce Elliott measured data http://www.ncbi.nlm.nih.gov/pmc/arti...81/table/tbl2/

Topspin forehand (forward direction)
Approximate contributions to impact racquet velocity (%)
Shoulder 15
Upper arm - Horizontal flexion 25
Upper arm - Internal rotation 40
Hand 20

IMO, shoulder means: power from legs, core, and etc.
This power produces just 15% of the racket velocity.
The arm and its parts create 85%.
Thus, the arm actions are much much much more important than legs, core, and etc actions!!!

[user92626]

Originally Posted by ho

The body do contribute to the the speed of your arm. But the main power of your arm is not by itself, but by the fact that body slow down:
Run 25m/h on the train with 50m/h your speed is absolutely 75m/h. Now if the train suddenly stop: You will get kill by your enormous speed instantly.

Killed by enormous speed?

What kind of logics is this?


If you got killed from that, it would likely be from slamming your face on the ground or something similar.

[albesca]

Originally Posted by toly

Your statement contradicts with Bruce Elliott measured data http://www.ncbi.nlm.nih.gov/pmc/arti...81/table/tbl2/

Topspin forehand (forward direction)
Approximate contributions to impact racquet velocity (%)
Shoulder 15
Upper arm - Horizontal flexion 25
Upper arm - Internal rotation 40
Hand 20

IMO, shoulder means: power from legs, core, and etc.
This power produces just 15% of the racket velocity.
The arm and its parts create 85%.
Thus, the arm actions are much much much more important than legs, core, and etc actions!!!

This i what i feel Toly.. without using biceps and forearm is impossible or so to transmit great amount of energy on the ball ... but this your last one is an exaggeration : "Thus, the arm actions are much much much more important than legs, core, and etc actions!!!"

The kinetic chain energy as a sequential sum of its segments energy, it's a myth. Each segment affect the operation of the other, don't add, so imho, to produce its 85%, the arm absolutely needs that 15% body work. Therefore, by me, despite their contribution in terms of energy is vastly different, their importance is the same.

What I do not agree is keep repeating that the legs and trunk are the mainly responsible for power. This causes players to forget the arm and lost years to strengthen legs and abdomen without seeing concrete results in terms of power ( but many other advantages..)... until one day, by accident, they decide to put a lot of attention and a lot of energy also in their arm.

[SystemicAnomaly]

^ The role of the biceps is not as important as you seem to think. I do not see any forceful use of the biceps until late in the follow-thru. But I do agree that the role of the body -- legs, hip rotation, torso rotation -- is important.

Not certain that I agree with your assessment of th kinetic chain. The various links in the chain accumulate and transfer energy to the next link in the chain. In the study referenced by toly (above), Brian Elliot states, "In strokes where power is required (such as the service and groundstrokes), a number of body segments must be coordinated in such a way that a high racquet speed is generated at impact."

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

I don't believe that most players are in any real danger of not developing sufficient arm strength for tennis. Exercises to protect the shoulder/rotator group should be perfromed, but developing a lot of arm strength is not really all that crucial.
.

[Limpinhitter]

Originally Posted by rkelley

toly, maxpotapov, and albesca, here are some video links to pro forehands.

Here's Fed's forehand with some good analysis: http://www.youtube.com/watch?v=ydMHJGpypQE

Here's Djokovic's forehand: http://www.youtube.com/watch?v=y8AJY...eature=related
No analysis on this one but you can see (or at least I can) the same action of the shoulders whipping the arm around. Note that Djokovic is using a Western grip.

And then there are the two Lock and Roll videos that explain the concept and teach the forehand:
http://www.youtube.com/watch?v=Wwg9DB8S8a8
http://www.youtube.com/watch?v=EMNtq...eature=related

Give this stuff a try.

I think the L&R guy understands and teaches modern groundstrokes as well as anyone I've seen online.

PS: Your second link to the L&R guy is bad. Is this what you were looking for? http://www.youtube.com/watch?v=EMNtq...eature=related

[rkelley]

Originally Posted by Limpinhitter

I think the L&R guy understands and teaches modern groundstrokes as well as anyone I've seen online.

PS: Your second link to the L&R guy is bad. Is this what you were looking for? http://www.youtube.com/watch?v=EMNtq...eature=related

Thanks for the link fix. I'll try to correct the original post.

[albesca]

I don't see so much difference.

Brian Elliot says "In strokes where power is required (such as the service and groundstrokes), a number of body segments must be coordinated in such a way that a high racquet speed is generated at impact."

Agree .. and It's exactly what i would say here:
"The kinetic chain energy as a sequential sum of its segments energy, it's a myth. Each segment affect the operation of the other, don't add"

You have right, i forgotten all muscles involved around the shoulder joint.

If the technique is correct, the swing itself is a constant practice for arm muscles. Surely we would develop the speed of the arm, and not strength.

Thank you Sys
Ciao
Al

[DavaiMarat]

Originally Posted by SystemicAnomaly

^ The role of the biceps is not as important as you seem to think. I do not see any forceful use of the biceps until late in the follow-thru. But I do agree that the role of the body -- legs, hip rotation, torso rotation -- is important.

Not certain that I agree with your assessment of th kinetic chain. The various links in the chain accumulate and transfer energy to the next link in the chain. In the study referenced by toly (above), Brian Elliot states, "In strokes where power is required (such as the service and groundstrokes), a number of body segments must be coordinated in such a way that a high racquet speed is generated at impact."

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

I don't believe that most players are in any real danger of not developing sufficient arm strength for tennis. Exercises to protect the shoulder/rotator group should be perfromed, but developing a lot of arm strength is not really all that crucial.
.

I agree with this post.

[toly]

Originally Posted by albesca

"The kinetic chain energy as a sequential sum of its segments energy, it's a myth. Each segment affect the operation of the other, don't add"

I disagree with this statement.
Let’s assume we rotate torso around the spine with fixed passive straight arm. Since the arm is connected to the shoulder, it inevitably begins moving and therefore it gains kinetic energy. Thus, some segments of the body can add energy to other ones. But, I think this is obvious and you certainly understand that.

[toly]

Originally Posted by SystemicAnomaly

... But I do agree that the role of the body -- legs, hip rotation, torso rotation -- is important.

Can you provide any serious proof?

I think that 15% contribution to the racquet speed is not very important for the reason that we have to waste a lot of energy to create fast rotation of 130 - 200 pounds body. IMO it is better first to concentrate on arm actions and then on the body. The arm is much more important. In tennis everything is important, however with varying degrees of importance.

[maxpotapov]

Originally Posted by toly

I disagree with this statement.
Let’s assume we rotate torso around the spine with fixed passive straight arm. Since the arm is connected to the shoulder, it inevitably begins to move and therefore it gains kinetic energy. Thus, some segments of the body can add energy to other ones. But, I think this is obvious and you certainly understand that.

As I understood Albesca, it's not just arithmetic sum, but there's a progression in how parts align and interact to create optimal conditions for fastest racquet acceleration at the point of impact.

I would also argue, that even if PROPER coordination/rotation of lower/upper body contributes only 15% to the racquet speed, LACK THEREOF might cause a 40% slow down.

[Limpinhitter]

Originally Posted by toly

Your statement contradicts with Bruce Elliott measured data http://www.ncbi.nlm.nih.gov/pmc/arti...81/table/tbl2/

Topspin forehand (forward direction)
Approximate contributions to impact racquet velocity (%)
Shoulder 15
Upper arm - Horizontal flexion 25
Upper arm - Internal rotation 40
Hand 20

IMO, shoulder means: power from legs, core, and etc.
This power produces just 15% of the racket velocity.
The arm and its parts create 85%.
Thus, the arm actions are much much much more important than legs, core, and etc actions!!!

I think what rKelley is saying, which I concur with, is that Bruce Elliot's data does not withstand the scrutiny of practical experience to the contrary. "The proof of the pudding is in the eating," as they say.

[Limpinhitter]

Originally Posted by albesca

Absolutely agree, the arm do nothing without the loading from the legs and core.

But i still on my idea the trunk doesn't have volountary to drag. It musn't rotate as fast as possible.. legs haven't to work in that way during the forward swing.
The shoulder joint have to move at exactly speed needed by the arm... not less... but not more... because the dragging doesn't add power, but by me, destroy the arm coordination.

Ahhh! That's another issue. Your original premise was that UBR played no role in racquet speed. If you rotate as fast as possible, the connection between upper body rotation and arm swing becomes disconnected, because the UBR has completed before the arm swing has begun, and any benefit is lost. There is, however, an optimum speed at which the contribution of UBR to arm swing is maximized. I don't know how to calculate that value, which would be of no practical benefit anyway. But, I know it when I feel it, which is much more useful and practical.