PDA

View Full Version : The arm is not dragging by the body


albesca
12-31-2011, 01:55 AM
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

papa
12-31-2011, 06:06 AM
Well, first of all we're interested in racquet "head" speed and its not just generated by the arm - far from it. Most lower level player use way too much arm in playing this sport and as a result either end up with arm/shoulder injuries, are totally inconsistent, can't generate much pace, etc. When just the arm is involved, there is excessive lateral movement into the ball as compared with rotation. When just lateral movement is involved the stroke is very sluggish and just won't hold up.

So, in my opinion, you have this a little bit backwards.

albesca
12-31-2011, 09:01 AM
Tank you Papa for ur opinion. I don't talk about all the stroke .. i'm talking only about the forward swing. Before, body works hard for positioning and loading... but as the forward swing starts I think the body must reduce its role about to do the correct footwork and upper body would have to uncoils following the arm, and not driving it.

rkelley
12-31-2011, 09:26 AM
Tank you Papa for ur opinion. I don't talk about all the stroke .. i'm talking only about the forward swing. Before, body works hard for positioning and loading... but as the forward swing starts I think the body must reduce its role about to do the correct footwork and upper body would have to uncoils following the arm, and not driving it.

Well, I would advise the opposite of what you're saying here. The legs, trunk, and shoulders provide the power. They start the swing. The arms and the racquet whip around and the head of the racquet whips into the ball. The arms and wrist do some fine tuning as to exactly when the whip is cracked and exactly where the racquet head goes - that's why you keep your eye on the ball through impact - but the legs, trunk, and shoulders start the swing and provide the power.

spacediver
12-31-2011, 09:28 AM
Just because the arm is swinging around joint X doesn't mean that the momentum is generated at joint X.

Think of a whip - the tip of the whip breaks the speed of sound, but all the momentum is generated in the heavy handle.

toly
12-31-2011, 01:33 PM
Well, I would advise the opposite of what you're saying here. The legs, trunk, and shoulders provide the power. They start the swing. The arms and the racquet whip around and the head of the racquet whips into the ball. The arms and wrist do some fine tuning as to exactly when the whip is cracked and exactly where the racquet head goes - that's why you keep your eye on the ball through impact - but the legs, trunk, and shoulders start the swing and provide the power.

When we rotate trunk with acceleration, IMO the passive arm will never whip around the body. Thus, the arm and its parts should be active, or we should slow down trunk acceleration. Does it make any sense?
If trunk doesn’t rotate at all, the arm by itself still can rotate around shoulder joint etc. I believe that good athlete can hit 100 mph FH without trunk rotation, by using just active arm motions. He will never be able to do that with passive arm relying on whip effect. I tried it many times and always got pathetic FH.:)

maxpotapov
01-01-2012, 03:39 AM
When we rotate trunk with acceleration, IMO the passive arm will never whip around the body. Thus, the arm and its parts should be active, or we should slow down trunk acceleration. Does it make any sense?
If trunk doesn’t rotate at all, the arm by itself still can rotate around shoulder joint etc. I believe that good athlete can hit 100 mph FH without trunk rotation, by using just active arm motions. He will never be able to do that with passive arm relying on whip effect. I tried it many times and always got pathetic FH.:)

My experience, pretty much. But all those exercises helped me to improve my body positioning, posture, core and back muscles etc.
Now I simply add arm/wrist/fingers action to turn racquet head around, once I got fundamentals (lower/upper body) right.

It is simple physics: during body rotation centrifugal forces pull racquet forward/away, not around the body. There is no physical way racquet shaft will bump against your left shoulder on follow through if your hitting arm is all passive during upper body rotation.

albesca
01-01-2012, 04:41 AM
Well, I would advise the opposite of what you're saying here. The legs, trunk, and shoulders provide the power. They start the swing. The arms and the racquet whip around and the head of the racquet whips into the ball. The arms and wrist do some fine tuning as to exactly when the whip is cracked and exactly where the racquet head goes - that's why you keep your eye on the ball through impact - but the legs, trunk, and shoulders start the swing and provide the power.

Obiouvsly there are many ways to hit the ball on the other side of the court. What I believe is that it is impossible or so to produce an heavy ball without producing an high raquet head speed... and by dragging the arm whit the trunk i don't believe it is reliable.

Sure, the more fast we want to swing the arm, the more we have to be able to rotate the trunk fast, that mean great body and legs work .. but not the opposite.

Ironically, a too fast trunk rotation can disturb the swinging of the arm instead to help it on swinging fast.

When we rotate trunk with acceleration, IMO the passive arm will never whip around the body. Thus, the arm and its parts should be active, or we should slow down trunk acceleration. Does it make any sense? If trunk doesn’t rotate at all, the arm by itself still can rotate around shoulder joint etc. . I believe that good athlete can hit 100 mph FH without trunk rotation, by using just active arm motions. He will never be able to do that with passive arm relying on whip effect. I tried it many times and always got pathetic FH

Agree Toly, exactly what I would say.


Now I simply add arm/wrist/fingers action to turn racquet head around, once I got fundamentals (lower/upper body) right.

Absolutely agree Max.

rkelley
01-01-2012, 09:09 AM
When we rotate trunk with acceleration, IMO the passive arm will never whip around the body. Thus, the arm and its parts should be active, or we should slow down trunk acceleration. Does it make any sense?
If trunk doesn’t rotate at all, the arm by itself still can rotate around shoulder joint etc. I believe that good athlete can hit 100 mph FH without trunk rotation, by using just active arm motions. He will never be able to do that with passive arm relying on whip effect. I tried it many times and always got pathetic FH.:)

When folks talk about "passive arm" it's not to say the muscles in the chest, arm and wrist are not being used, but the majority of the power is coming from the core rotation that starts with the legs, then through the hips and shoulders. Assuming that the arm is still attached to the shoulder at this point it has to whip around the body.

Check out this video, 0:36. This is what's happening: http://www.youtube.com/watch?v=EMNtq...eature=related

And here's a video that shows the whipping action in the full forehand stroke: http://www.youtube.com/watch?v=EMNtq393tvo&feature=related

If you try to hit 100 mph forehands with just your arms, assuming that's even possible, I think you'll tear your shoulder apart pretty quickly.

rkelley
01-01-2012, 09:30 AM
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=y8AJYfkJ4hc&feature=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=EMNtq393tvo&feature=related

Give this stuff a try.

5263
01-01-2012, 09:30 AM
When we rotate trunk with acceleration, IMO the passive arm will never whip around the body. Thus, the arm and its parts should be active, or we should slow down trunk acceleration. Does it make any sense?
If trunk doesn’t rotate at all, the arm by itself still can rotate around shoulder joint etc. I believe that good athlete can hit 100 mph FH without trunk rotation, by using just active arm motions. He will never be able to do that with passive arm relying on whip effect. I tried it many times and always got pathetic FH.:)

IMO you and the OP make some good points here and that maybe the
body does more to position the arm so that then the arm can create the
acceleration of the racket. Oscar often talks of how much the biceps are
involved.

papa
01-01-2012, 09:46 AM
When folks talk about "passive arm" it's not to say the muscles in the chest, arm and wrist are not being used, but the majority of the power is coming from the core rotation that starts with the legs, then through the hips and shoulders. Assuming that the arm is still attached to the shoulder at this point it has to whip around the body.

Check out this video, 0:36. This is what's happening: http://www.youtube.com/watch?v=EMNtq...eature=related

And here's a video that shows the whipping action in the full forehand stroke: http://www.youtube.com/watch?v=EMNtq393tvo&feature=related

If you try to hit 100 mph forehands with just your arms, assuming that's even possible, I think you'll tear your shoulder apart pretty quickly.

Well, this is certainly how I see this whole process. I know, and frequently see, other attempts at hitting the forehand but I just don't happen to agree with them.

I know for example of a guy that can absolutely smack the ball and he stays on the rear foot throughout the stroke. For him, "maybe" it works to a degree but I honestly believe that as good as he presently is (I'm taking forehand) he would be that much better if he used the example provided by rkelley. Can he hit the ball with more pace than me - yeah, probably but I'd win hands down when it comes to consistency and placement. He isn't all arm by the way and is able to generate wicked racquet head speed coming across the body which I like - I just like more weight transfer.

I know some don't care to move away from their all arm approach and I realize that for them, it might work. Many have learned this game when racquet/string technology didn't play such a significant role - that's just not the case anymore.

rkelley
01-01-2012, 11:26 AM
I've learned this whole modern forehand "thing" and letting my arm whip around in the last year. It's been an adventure.

I'll say that for me it's taken a fair number of hours of practice to get the feel of it. At first, when I did it correctly, it felt great, but other times I'd miss time it. I wasn't feeling the arm whip and I wasn't getting any power. Some days I'd really have it, and then I'd struggle the next time out. I kept at it, practiced on the wall, and now it's pretty automatic.

Relative to my old school forehand the two biggest improvements are greater spin and consistently hitting with more power - and they're linked. I can get a lot more topspin than I used to be able to. This is critical for getting shots to land in that would otherwise go out. I can also hit with greater power in all positions on the court. When I have to I can just stay in a totally open stance, reach across with my left arm and take the racquet back, and rip a pretty decent forehand. But without the topspin all that extra power would launch balls long.

As I've gotten better at hitting this forehand it really cool how much racquet head speed I can get without really swinging that hard. The racquet head just naturally whips around. I can control the swing path so that I can control the amount of topspin verses hitting through the ball.

toly
01-01-2012, 11:38 AM
... but the majority of the power is coming from the core rotation that starts with the legs, then through the hips and shoulders.

This is a very bold statement. You are a Mechanical Engineer. Can you prove your claims using the scientific approach? Please feel free to employ any formula, the laws of physics, math, etc.

Happy New Year!:)

albesca
01-01-2012, 11:53 AM
If you try to hit 100 mph forehands with just your arms, assuming that's even possible, I think you'll tear your shoulder apart pretty quickly.

No doubt, agree with this point 100 percent. Only I think the trunk doesn't drag..

Dragging the arm, trying to maintain a constant angle at the elbow joint, results in an isometric or so biceps action that stiffens the swing.

This is ok if I have to manage an hard ball .. but I'd clearly divides the cases where our priority is to accelerate the racket head from where our priority is to maintain a stable head of the racket, and this depends, at first, on the speed of the incoming ball.

By me seems to have great raq. head acceleration, the elbow needs some independence form the shoulder joint.. this mean, at the end, to have active biceps during the forward swing.

IMO you and the OP make some good points here and that maybe the body does more to position the arm so that then the arm can create the acceleration of the racket. Oscar often talks of how much the biceps are involved.

I don't know so much about the Oscar Wegner method, only here I read something, but agree , biceps , forearm pronator and fingers tendons .. imho have the control of the raquet head acceleration.

ho
01-02-2012, 06:42 AM
This is a very bold statement. You are a Mechanical Engineer. Can you prove your claims using the scientific approach? Please feel free to employ any formula, the laws of physics, math, etc.

Happy New Year!:)
1/Leg and core rotation provide the major power in rotational movement
2/Arm whip around shoulder provide the most racket speed in linear movement.
(1) provide speed if you hit with body and arm as one unit. Not the racket speed that give you the ball speed, but the compression of the ball against a solid object self create the ball speed.
(2) provide racket speed but their is only the arm weight behind the racket, law of physic on colliding will indicate that ball speed will not always as much as (1) particular when ball coming in great speed.

The best way is to combine both:
You hit with arm and body as one unit
Right by the time after contact, whip out your arm forward for more speed and spin.
Saying it is easy, but doing it need great timing and accuracy:
You extend your arm out by:
1/ keeping your arm loose
2/ time the push out of your arm by using your left hand: drop to the chest early will launch your right shoulder at the right moment.

rkelley
01-02-2012, 08:00 AM
... but the majority of the power is coming from the core rotation that starts with the legs, then through the hips and shoulders.


This is a very bold statement. You are a Mechanical Engineer. Can you prove your claims using the scientific approach? Please feel free to employ any formula, the laws of physics, math, etc.

Happy New Year!:)

Hi Toly. I don't think of this statement as being bold or controversial. Go to just about any instruction site and you'll see something similar said. It's completely consistent with what I see when I watch pros and high level players hit, and it's completely consistent with my own personal experience.

Meaning no disrespect, but it just seems really obvious to me. Yes, I am a mechanical engineer. As an engineer I'd tell you that muscles groups in your legs and core are far stronger than the muscles in your shoulder alone. Wouldn't it make sense to utilize those stronger muscle groups in generating power? An analytical analysis would need to take into account.

Seriously, just go out and hit some balls. Can you hit it harder when you use just your arm, or when you use your legs and body too? Do what works for you and have fun.

toly
01-03-2012, 12:23 PM
1/Leg and core rotation provide the major power in rotational movement
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 pounds and just a little bit is going to the ball.

2/Arm whip around shoulder provide the most racket speed in linear movement.
If arm is passive and moves like the whip, it cannot produce decent linear racquet speed.

(1) provide speed if you hit with body and arm as one unit.
It cannot provide a lot of speed because body and arm as one unit has very big mass. Thus, this unit would be relatively slow, compare with elbow or wrist motions.

Not the racket speed that give you the ball speed, but the compression of the ball against a solid object self create the ball speed.
The ball speed approximately is

Vballspeed = Vracquetspeed x (1 +K), (1)

Where K is coefficient of restitution.

If the racket has speed 80 mph, K is around 0.3. So, the compression of the ball cannot be the main factor. According to formula (1), the racquet speed is the main factor of the ball speed.


(2) provide racket speed but their is only the arm weight behind the racket, law of physic on colliding will indicate that ball speed will not always as much as (1) particular when ball coming in great speed.
See please my posts: http://tt.tennis-warehouse.com/showthread.php?p=5892760#post5892760, http://tt.tennis-warehouse.com/showthread.php?p=5895380#post5895380

DavaiMarat
01-03-2012, 12:37 PM
Tank you Papa for ur opinion. I don't talk about all the stroke .. i'm talking only about the forward swing. Before, body works hard for positioning and loading... but as the forward swing starts I think the body must reduce its role about to do the correct footwork and upper body would have to uncoils following the arm, and not driving it.

You are partly right about this accessment but also partly wrong. I would have to agree with papa, the body plays an importantly role in coiling, the body also uncoils as you bring the racquet out of the slot and forward unto the ball. If you look from the slot and contact the arm doesn't really move that much save for the forearm. As you continue into the forward swing the body stops rotation to allow the arm to 'snap' around the shoulder axis finishing the 2nd to last part of the kinetic chain (wrist being the last). Not very often will you find players extending the fully 180 degrees. Djokovic may be an exception to this rule.

So yes the body rotation stops acts like a fulcrum against the arm but it's the body who initializes the forward swing.

Read the article 'The arms swings the least' at tennisone.com...you will grasp the concept.

I like to think of this way. The arm lifts, the body hits!

toly
01-03-2012, 12:38 PM
When folks talk about "passive arm" it's not to say the muscles in the chest, arm and wrist are not being used,
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.:???:

rkelley
01-03-2012, 12:47 PM
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
01-03-2012, 01:14 PM
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
01-03-2012, 02:00 PM
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
01-03-2012, 02:16 PM
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
01-03-2012, 02:26 PM
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
01-03-2012, 02:34 PM
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
01-03-2012, 03:06 PM
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
01-03-2012, 04:06 PM
... 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/articles/PMC2577481/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
01-03-2012, 04:27 PM
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
01-04-2012, 12:31 AM
Your statement contradicts with Bruce Elliott measured data http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/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
01-04-2012, 05:51 AM
^ 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
01-04-2012, 08:15 AM
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=y8AJYfkJ4hc&feature=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=EMNtq393tvo&feature=related

rkelley
01-04-2012, 08:33 AM
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=EMNtq393tvo&feature=related

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

albesca
01-04-2012, 08:35 AM
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
01-04-2012, 09:33 AM
^ 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
01-04-2012, 09:52 AM
"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
01-04-2012, 10:17 AM
... 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
01-04-2012, 11:28 AM
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
01-04-2012, 11:31 AM
Your statement contradicts with Bruce Elliott measured data http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/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
01-04-2012, 11:39 AM
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.

ho
01-04-2012, 01:10 PM
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.
I'm sorry, if you slam on something

ho
01-04-2012, 01:16 PM
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.:)
Ball is a soft object, on impact it deformed, the harder you hit, the more it deformed, the more it deformed, the more it stay on the string bed, the more it stay on string bed, the more it bounce out.
Oscar is a tennis coach, he is not a scientist.
Just hit the heck out of the ball, arm and body as one unit, you will have such an easy time on the court.

toly
01-04-2012, 01:27 PM
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.
Yes, I agree with you.

The problem is that we don’t know ideal procedure on how to hit FH. After 30 years from now, current FH technique probably would be ridiculous. But, at least we should try to understand what is really very important and what is not.

For example, Lock&Roll coach emphasizes too much importance of the hips and body rotation. But, when he demonstrates FH, his arm and its parts (including wrist) are very active. That’s why I dislike his monkey’s drum idea. IMO he puts wrong accents in his explanations.

Dellon
01-04-2012, 02:09 PM
Interesting study I found ... compares the major differences between novice and expert players. the ones marked with an * shows significant differences between the two: upper trunk and wrist

http://www.sph.umd.edu/KNES/faculty/jkshim/NEASB/abstracts/46%20-50.pdf

Dellon
01-04-2012, 02:17 PM
and one more a bit more comprehensive

http://www.jssm.org/vol9/n4/15/v9n4-15pdf.pdf

Dellon
01-04-2012, 02:33 PM
to me this is the ultimate position in tennis with your upper body facing the net ... when I hit a forehand I always think I'm hitting it with my chest and when I do that everyhting else works perfectly.

H:\My Pictures\forehand.jpeg

Dellon
01-04-2012, 02:35 PM
how do I attach a picture?

Dellon
01-04-2012, 02:44 PM
this is what I'm thinking that I am when I rotate my body and hit a forehand ...teh top handle is my shoulders and chest) ... just imagine it has a spring at the bottom ... you twist it to the right and then release it ... no hip rotation no other things ... they happen naturally as they all conect you to the ground

http://www.advdesigns.com/ro14insptdr.html

toly
01-04-2012, 02:59 PM
Ball is a soft object, on impact it deformed, the harder you hit, the more it deformed, the more it deformed, the more it stay on the string bed, the more it stay on string bed, the more it bounce out.
The harder we hit the ball, the more it is deformed and damaged. The damage of the ball is essential.
If we hit ball with racquet speed 1 mph, coefficient of restitution (if I remember correctly) will be around 70%. If racquet speed is 80 mph, this coefficient is just 30%. Thus, scientific data disagree with your statement.

Just hit the heck out of the ball, arm and body as one unit, you will have such an easy time on the court.
If we rotate fixed passive arm and body as one unit, we will produce around 15% of the possible maximum of the racquet speed. See please Elliot data.

maxpotapov
01-04-2012, 03:23 PM
For example, Lock&Roll coach emphasizes too much importance of the hips and body rotation. But, when he demonstrates FH, his arm and its parts (including wrist) are very active. That’s why I dislike his monkey’s drum idea. IMO he puts wrong accents in his explanations.

That's most likely due to assumption, that novice/recreational players use their arm only, and hips/body rotation is counter intuitive and thus must be overemphasized.

I personally think it's a good way to start, as developing proper fundamentals is difficult (counter intuitive, energy inefficient) yet essential. But once body starts moving and working, it's time to explore those 85% that accelerate racquet head through the contact point.

albesca
01-05-2012, 12:44 AM
..For example, Lock&Roll coach emphasizes too much importance of the hips and body rotation. But, when he demonstrates FH, his arm and its parts (including wrist) are very active. That’s why I dislike his monkey’s drum idea. IMO he puts wrong accents in his explanations.

Yes Toly, i'm watched along L&R forehand video and I have come to your own conclusions !! :)

albesca
01-05-2012, 12:55 AM
how do I attach a picture?

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.

Ciao
Al

rkelley
01-05-2012, 07:37 AM
For example, Lock&Roll coach emphasizes too much importance of the hips and body rotation. But, when he demonstrates FH, his arm and its parts (including wrist) are very active. That’s why I dislike his monkey’s drum idea. IMO he puts wrong accents in his explanations.

Yes Toly, i'm watched along L&R forehand video and I have come to your own conclusions !! :)

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.

ho
01-05-2012, 08:24 AM
The harder we hit the ball, the more it is deformed and damaged. The damage of the ball is essential.
If we hit ball with racquet speed 1 mph, coefficient of restitution (if I remember correctly) will be around 70%. If racquet speed is 80 mph, this coefficient is just 30%. Thus, scientific data disagree with your statement.
Damaging ???
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.

If we rotate fixed passive arm and body as one unit, we will produce around 15% of the possible maximum of the racquet speed. See please Elliot data.
Sure, but the mass behind it as 10 time larger. result in the ball speed will be more.
Think, Toly, think.

toly
01-05-2012, 11:34 AM
Damaging ???
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.
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).

Sure, but the mass behind it as 10 time larger. result in the ball speed will be more.
Think, Toly, think.
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.

albesca
01-05-2012, 03:02 PM
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.

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.

user92626
01-05-2012, 03:13 PM
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.

SystemicAnomaly
01-06-2012, 01:02 AM
... 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.

... 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.

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.
.

bhupaes
01-06-2012, 01:13 PM
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.

bhupaes
01-06-2012, 01:59 PM
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... :)

toly
01-06-2012, 02:19 PM
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.:)

toly
01-06-2012, 03:03 PM
Don't really know exactly what Brian Elliot means by this 15% contribution. ... the 15% figure appears to be rather misleading.
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.:confused:

bhupaes
01-06-2012, 03:43 PM
Wow, this is maybe first time I agree with you. Thanks.:)

Great! What the heck, it's Friday, I'll drink a beer to that! :)

toly
01-06-2012, 04:54 PM
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

Where

Ѡbody = 7 rad/sec; Ѡshoulder = 10 rad/sec; Ѡwrist = 50 rad/sec;

Rbody = 70”; Rshoulder=50”; Rwrist = 25”;

Thus

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.:)

maxpotapov
01-06-2012, 10:45 PM
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%.

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.

5263
01-06-2012, 11:00 PM
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.

maxpotapov
01-06-2012, 11:07 PM
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

5263
01-06-2012, 11:33 PM
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.

maxpotapov
01-06-2012, 11:55 PM
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.)

albesca
01-07-2012, 05:48 AM
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....

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.

SystemicAnomaly
01-08-2012, 03:55 AM
^ 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.

maxpotapov
01-08-2012, 04:11 AM
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.

SystemicAnomaly
01-08-2012, 04:29 AM
^ 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.

albesca
01-08-2012, 07:24 AM
There is a difference between reality and perception.....

Absolutely Max... and I could understand better if my teacher would explains
using the perceptions i have to feel ..

ho
01-08-2012, 12:16 PM
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

Where

Ѡbody = 7 rad/sec; Ѡshoulder = 10 rad/sec; Ѡwrist = 50 rad/sec;

Rbody = 70”; Rshoulder=50”; Rwrist = 25”;

Thus

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.:)
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)

toly
01-08-2012, 12:54 PM
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?:confused:

ho
01-08-2012, 05:49 PM
I’m sorry, but our mutual understanding looks really very bad. Can you tell us about your education?:confused:
As much as you can go thru University, max post graduate and everything in Nam war 30 years back, you will find me.

toly
01-08-2012, 06:41 PM
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.:(

maxpotapov
01-09-2012, 12:30 AM
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 ;)

toly
01-09-2012, 08:14 AM
Toly, you truly are one of the most delicate tennis players in the world ;)
Thank you Max.:)

My experience, pretty much. But all those exercises helped me to improve my body positioning, posture, core and back muscles etc.
… Now I simply add arm/wrist/fingers action to turn racquet head around, once I got fundamentals (lower/upper body) right.
I’ve read in others threads your posts about fingers action. Could you clarify this?

maxpotapov
01-09-2012, 08:40 AM
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.

toly
01-09-2012, 09:13 AM
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

maxpotapov
01-09-2012, 12:56 PM
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 :)

bhupaes
01-09-2012, 01:06 PM
^ 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.

Thanks SA. What you're saying is exactly my model of how the legs contribute.

DropShotArtist
12-27-2012, 10:51 PM
So was this thread ever reconciled? Passive arm whipped across body or not?

ShoeShiner
12-28-2012, 01:05 AM
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.

dominikk1985
12-28-2012, 08:11 AM
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.

DropShotArtist
12-28-2012, 10:59 AM
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?

dominikk1985
12-28-2012, 11:09 AM
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:
http://www.brianmac.co.uk/javelin/photo.htm

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.

DropShotArtist
12-28-2012, 11:36 AM
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:
http://www.brianmac.co.uk/javelin/photo.htm

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?

DropShotArtist
12-28-2012, 11:40 AM
^^^ 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?

ski racer
12-30-2012, 11:10 AM
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?

dominikk1985
12-30-2012, 11:44 AM
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.

toly
12-30-2012, 03:36 PM
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?

http://i47.tinypic.com/6jqetf.jpg

http://i48.tinypic.com/k53i52.jpg

Internal shoulder rotation is counterclockwise upper arm rotation.

http://i50.tinypic.com/23kre3o.jpg

In picture below Serena Williams is trying to hit hard FH winner. Here is original video http://www.youtube.com/watch?v=BJg5cWEviZo.

http://i49.tinypic.com/t98kjn.jpg

Her main arm’s motions around contact are:
1. Arm flexion.
2. Internal shoulder rotation.
3. Forearm pronation.
4. Wrist ulnar deviation.