The arm is not dragging by the body

[toly]

Originally Posted by bhupaes

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]

Originally Posted by SystemicAnomaly

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.

[bhupaes]

Originally Posted by toly

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]

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]

Originally Posted by toly

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]

Originally Posted by maxpotapov

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]

Originally Posted by 5263

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]

Originally Posted by maxpotapov

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]

Originally Posted by 5263

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]

Originally Posted by bhupaes

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]

^ 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]

Originally Posted by SystemicAnomaly

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]

^ 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]

Originally Posted by maxpotapov

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]

Originally Posted by toly

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]

Originally Posted by ho

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?

[ho]

Originally Posted by toly

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.

[toly]

Originally Posted by ho

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]

Originally Posted by toly

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]

Originally Posted by maxpotapov

Toly, you truly are one of the most delicate tennis players in the world

Thank you Max.

Originally Posted by maxpotapov

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?