The arm is not dragging by the body

[maxpotapov]

Originally Posted by toly

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]

Originally Posted by maxpotapov

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/showt...92#post5954592 and http://tt.tennis-warehouse.com/showt...29#post5309329

[maxpotapov]

Originally Posted by toly

Yes, I agree.
Something like that I described in posts: http://tt.tennis-warehouse.com/showt...92#post5954592 and http://tt.tennis-warehouse.com/showt...29#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]

Originally Posted by 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.

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

[DropShotArtist]

So was this thread ever reconciled? Passive arm whipped across body or not?

[ShoeShiner]

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]

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]

Originally Posted by dominikk1985

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]

Originally Posted by DropShotArtist

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]

Originally Posted by dominikk1985

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]

^^^ 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]

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]

Originally Posted by ski racer

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]

Originally Posted by ski racer

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?

Internal shoulder rotation is counterclockwise upper arm rotation.



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



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