Standford University Graphic on Serve

[gzhpcu]

Shows the acceleration of the racket as the body parts slow down creating the whip effect.

[klacr]

So the million dollar question. What does it all mean?


Kyle LaCroix USPTA
Boca Raton

[gzhpcu]

It means that you have to brake your body parts to impart speed to the next part, culminating with the wrist/racket.

It also means to aim up at the ball, since this causes the body parts to brake, instead to to aim forward.

[stotty]

It means that you have to brake your body parts to impart speed to the next part, culminating with the wrist/racket.

It also means to aim up at the ball, since this causes the body parts to brake, instead to to aim forward.

Yes, I seem to remember 10splayer saying as much in another thread...on the forehand...holding the line with the rear leg to delay rotation. I guess the theory applies to all shots.

[gzhpcu]

Think of a whip: You stop suddenly to get a crack of the whip.

[johnyandell]

Phil,

Got the url for the graphic.

Think the breaking happens--wouldn't want to try to consciously stop anything once you unleash...

[klacr]

It means that you have to brake your body parts to impart speed to the next part, culminating with the wrist/racket.

It also means to aim up at the ball, since this causes the body parts to brake, instead to to aim forward.

Perhaps, not something I want to force. I want my body going. Maybe kinetic chain can do its part. Don't wanna stop or brake on my own.


Kyle LaCroix USPTA
Boca Raton

[gzhpcu]

Phil,

Got the url for the graphic.

Think the breaking happens--wouldn't want to try to consciously stop anything once you unleash...

Right, I think it happens automatically if you think of serving up at the ball instead of out towards the court...

[johnyandell]

Phil,

Meant to ask, what is the url for that graphic.

[gzhpcu]

John,
Surfing, I picked up from this YouTube video...

https://www.youtube.com/watch?v=TESTQsMTvGQ

[tennis_chiro]

Angular velocity vs linear velocity

This graphic shows the actual linear velocity of the various body parts. It would be very interesting to see the associated angular rotation and speed of that angular rotation as the motion progresses. The film is fast enough and high definition enough. It would simply be a question of putting three sensors across the joints and then feeding the info into the computer. At least I would think so. It would be very interesting to see how much shoulder internal rotation was taking place at each stage as Brian Gordon did in his articles on tennisplayer.

The graphic I want to see and comparison I want to see is the amount of lift off the ground and velocity and acceleration of that lift at the different points of the serve. I would be particularly interested in the height of the shoulder joint. Then I would want to correlate the height of the lift off the court with the speed of the serve. I'd also want to see it relative to the height of the individual. So the obvious question is, do the player's who get further off the ground actually hit the serve harder. Vic Braden's old video about force on the ground would seem to say no. I'd think the servers that are really leaping to serve are putting too much energy into getting off the ground and not enough into driving up to the ball.

What do you think, John?

don

[gzhpcu]

This graphic shows the actual linear velocity of the various body parts. It would be very interesting to see the associated angular rotation and speed of that angular rotation as the motion progresses. The film is fast enough and high definition enough. It would simply be a question of putting three sensors across the joints and then feeding the info into the computer. At least I would think so. It would be very interesting to see how much shoulder internal rotation was taking place at each stage as Brian Gordon did in his articles on tennisplayer.


don

Here it is:


source: Biomechanics of Advanced Tennis, Bruce Elliot, Macher Reid, Miguel Crespo, page 63

[tennis_chiro]

A little help please

Here it is:


source: Biomechanics of Advanced Tennis, Bruce Elliot, Macher Reid, Miguel Crespo, page 63

Okay, Phil

Let's see if there's any grey matter left up there with all those cobwebs.

First of all,
Angular momentum - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Angular_momentum
Wikipedia
For a rigid body the angular momentum can be expressed as the product of the body's moment of inertia, I, (i.e., a measure of an object's resistance to changes in its rotation velocity) and its angular velocity, ω.

Can we assume the moment of inertia is constant? Then this is really a measure of angular velocity for us here.

I need MEF, RLP, and MER. I got IMP is impact.

I would have thought as the body completed the motion the hips would be in positive CCR territory, but perhaps it is because they are slowing down that it goes so negative at that point.

Come on, Phil. Time to explain this to the rest of us. There's some interesting data here, although I don't think it is specific enough to answer the question I was postulating about the actual elbow vs the shoulder vs the wrist in terms of how much internal rotation was taking place at each joint at each stage of the motion.

don

[don_budge]

Too Much Information…The Police

Okay, Phil

Let's see if there's any grey matter left up there with all those cobwebs.

First of all,
Angular momentum - Wikipedia, the free encyclopedia
en.wikipedia.org/wiki/Angular_momentum
Wikipedia
For a rigid body the angular momentum can be expressed as the product of the body's moment of inertia, I, (i.e., a measure of an object's resistance to changes in its rotation velocity) and its angular velocity, ω.

Can we assume the moment of inertia is constant? Then this is really a measure of angular velocity for us here.

I need MEF, RLP, and MER. I got IMP is impact.

I would have thought as the body completed the motion the hips would be in positive CCR territory, but perhaps it is because they are slowing down that it goes so negative at that point.

Come on, Phil. Time to explain this to the rest of us. There's some interesting data here, although I don't think it is specific enough to answer the question I was postulating about the actual elbow vs the shoulder vs the wrist in terms of how much internal rotation was taking place at each joint at each stage of the motion.

don

As useful as a grave robber in a crematorium

As much use as an ashtray on a motorbike

As useless as a carpet fitters ladder

As useful as a one armed trapeze artist with an itchy arse

About as much use as a one legged cat trying to bury a turd on a frozen lake

As much use as mudguards on a tortoise

As much use as a one legged man at an arse kicking competition

As much use as Captain Hook at a gynaecologists convention

As much use as a trap door on a lifeboat



"Too Much Information"…The Police 1981

https://www.youtube.com/watch?v=SepLpUGn_O0

Too much information running through my brain
Too much information driving me insane
Too much information running through my brain
Too much information driving me insane

I've seen the whole world six times over
Sea of Japan to the Cliffs of Dover
Oh
I've seen the whole world six times over
Sea of Japan to the Cliffs of Dover
Oh

Overkill
Overview
Over my dead body
Over me
Over you
Over everybody

Too much information running through my brain
Too much information driving me insane
Too much information running through my brain
Too much information driving me insane

I've seen the whole world six times over
Sea of Japan to the Cliffs of Dover
Oh
I've seen the whole world six times over
Sea of Japan to the Cliffs of Dover
Oh

Too much information running through my brain
Too much information driving me insane
Too much information running through my brain
Too much information driving me insane

I've seen the whole world six times over
Sea of Japan to the Cliffs of Dover
Oh
I've seen the whole world six times over
Sea of Japan to the Cliffs of Dover
Oh

Overkill
Overview
Over my dead body
Over me
Over you
Over everybody

Too much information running through my brain
Too much information driving me insane
Too much information running through my brain
Too much information driving me insane
[to fade]

What does this have to do with the price of salt?

Just being ironic…this is of some interest to somebody but I highly doubt that it will enlighten anyone about the mechanics of the service motion. I can do the math…but it seems to me that takes the art and the beauty out of the darned thing. Too much information. As useless as tits on a bull.

[gzhpcu]

MER = maximum external rotation
MEF=maximum elbow flexion
RLP = Lowest Racket Point

Angular momentum of body = Moment of inertia about an axis x angular velocity (amount of rotation) about an axis.

We have 3 principal axes of rotation passing through the center of gravity: somersault, cartwheel and twist rotations.

We have a sequence of the force pyramid: (from bottom up):

• Ball
• Racquet
• Upper Extremity
• Trunk
• Legs
• Ground Reaction Forces

Everything occurs from bottom up.