The paradox of angular vs. linear momentum in the forehand and a possible solution.

spacediver

Hall of Fame
One of the themes of forehand instruction that never really made much sense to me was the idea of driving through the ball towards the target, while at the same time using rotation of the body to power the stroke.

The path that the racquet takes during the follow through is clearly a curved one (imagine a curve that is drawn on the plane parallel to the ground), yet we are often told not to swing across too much during contact, and rather to drive through the hitting zone.

To me, this sounded very strange. The body and arm should be rotating fluidly, and the idea of switching from a straight path to a curved path makes very little biomechanical sense.

But then, I realized that the wrist changes everything.

By gradually laying the wrist back more and more during the "linear" portion of the stroke, your arm can still be "helicoptering" but the racquet face will end up pointing in the direction of the target for an extended period of time (though it will be sliding towards the left ((for right handed forehand)) as it does so).

So if you were to view the stroke from above, and traced the path that the hand takes, it would be curved throughout the entire motion. But if you trace the angle of the racquet face, it spends the critical part of the stroke always facing the target.

The beauty of this is the motion dependent effect upon the wrist joint. If you keep a relaxed wrist, it will naturally lag behind (i.e. wrist joint will naturally extend).

Perhaps this is all common sense to many, but it was a bit of a revelation to me.

pushing_wins

Hall of Fame
omg
what are u talking about now?

spacediver

Hall of Fame
hehe sorry it's just that the damn article you sent me is hard to read. I've been lazy about getting round to replying to you, but I definitely like your reconciliation of the two perspectives.

(others, please ignore this and the above post).

pushing_wins

Hall of Fame
hehe sorry it's just that the damn article you sent me is hard to read. I've been lazy about getting round to replying to you, but I definitely like your reconciliation of the two perspectives.

(others, please ignore this and the above post).

did i send u an article? dont worry about it.

have bigger fish to fry with that delusional guy

pushing_wins

Hall of Fame
One of the themes of forehand instruction that never really made much sense to me was the idea of driving through the ball towards the target, while at the same time using rotation of the body to power the stroke.

The path that the racquet takes during the follow through is clearly a curved one (imagine a curve that is drawn on the plane parallel to the ground), yet we are often told not to swing across too much during contact, and rather to drive through the hitting zone.

To me, this sounded very strange. The body and arm should be rotating fluidly, and the idea of switching from a straight path to a curved path makes very little biomechanical sense.

But then, I realized that the wrist changes everything.

By gradually laying the wrist back more and more during the "linear" portion of the stroke, your arm can still be "helicoptering" but the racquet face will end up pointing in the direction of the target for an extended period of time (though it will be sliding towards the left ((for right handed forehand)) as it does so).

So if you were to view the stroke from above, and traced the path that the hand takes, it would be curved throughout the entire motion. But if you trace the angle of the racquet face, it spends the critical part of the stroke always facing the target.

The beauty of this is the motion dependent effect upon the wrist joint. If you keep a relaxed wrist, it will naturally lag behind (i.e. wrist joint will naturally extend).

Perhaps this is all common sense to many, but it was a bit of a revelation to me.

u are barking up the wrong tree

no wonder KM said just shut it and listen to me

spacediver

Hall of Fame
what's wrong with the analysis?

pushing_wins

Hall of Fame
what's wrong with the analysis?

its not the wrist as per me and KM

spacediver

Hall of Fame
what do you mean it's not the wrist? KM never talked to me about the wrist.

Are you saying the wrist shouldn't be laid back through contact? (I'm not saying that the wrist should never be more active, I just want to clarify your enigmatic reply).

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pushing_wins

Hall of Fame
what do you mean it's not the wrist? KM never talked to me about the wrist.

Are you saying the wrist shouldn't be laid back through contact? (I'm not saying that the wrist should never be more active, I just want to clarify your enigmatic reply).

when u push the elbow forward, the wrist naturally lays back

spacediver

Hall of Fame
when u push the elbow forward, the wrist naturally lays back

isn't that exactly what i said?

The beauty of this is the motion dependent effect upon the wrist joint. If you keep a relaxed wrist, it will naturally lag behind (i.e. wrist joint will naturally extend).

Besides, how the wrist is laid back is tangential. The main point of this thread was to discuss the fact that when the wrist is laid back, you end up with a racquet face that maintains its angle square to the net, even though the rest of the system is rotating.

pushing_wins

Hall of Fame
isn't that exactly what i said?

Besides, how the wrist is laid back is tangential. The main point of this thread was to discuss the fact that when the wrist is laid back, you end up with a racquet face that maintains its angle square to the net, even though the rest of the system is rotating.

spacediver

Hall of Fame
Interesting.

then what is the reconciliating factor?

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pushing_wins

Legend
One of the themes of forehand instruction that never really made much sense to me was the idea of driving through the ball towards the target, while at the same time using rotation of the body to power the stroke.

The path that the racquet takes during the follow through is clearly a curved one (imagine a curve that is drawn on the plane parallel to the ground), yet we are often told not to swing across too much during contact, and rather to drive through the hitting zone.

To me, this sounded very strange. The body and arm should be rotating fluidly, and the idea of switching from a straight path to a curved path makes very little biomechanical sense.

But then, I realized that the wrist changes everything.

By gradually laying the wrist back more and more during the "linear" portion of the stroke, your arm can still be "helicoptering" but the racquet face will end up pointing in the direction of the target for an extended period of time (though it will be sliding towards the left ((for right handed forehand)) as it does so).

So if you were to view the stroke from above, and traced the path that the hand takes, it would be curved throughout the entire motion. But if you trace the angle of the racquet face, it spends the critical part of the stroke always facing the target.

The beauty of this is the motion dependent effect upon the wrist joint. If you keep a relaxed wrist, it will naturally lag behind (i.e. wrist joint will naturally extend).

Perhaps this is all common sense to many, but it was a bit of a revelation to me.

not sure if i follow sll of this but in recent stroke improvement found this (wrist) out to be key for this player.

spacediver

Hall of Fame
what km said

KM recommends a completely different type of stroke, where the hips remain closed throughout the entire stroke.

I'm referring more to the standard open stance forehand.

spacediver

Hall of Fame
not sure if i follow sll of this but in recent stroke improvement found this (wrist) out to be key for this player.

I'll try to make an animation or a graphic when I get home.

C

chico9166

Guest
One of the themes of forehand instruction that never really made much sense to me was the idea of driving through the ball towards the target, while at the same time using rotation of the body to power the stroke.

The path that the racquet takes during the follow through is clearly a curved one (imagine a curve that is drawn on the plane parallel to the ground), yet we are often told not to swing across too much during contact, and rather to drive through the hitting zone.

To me, this sounded very strange. The body and arm should be rotating fluidly, and the idea of switching from a straight path to a curved path makes very little biomechanical sense.

But then, I realized that the wrist changes everything.

By gradually laying the wrist back more and more during the "linear" portion of the stroke, your arm can still be "helicoptering" but the racquet face will end up pointing in the direction of the target for an extended period of time (though it will be sliding towards the left ((for right handed forehand)) as it does so).

So if you were to view the stroke from above, and traced the path that the hand takes, it would be curved throughout the entire motion. But if you trace the angle of the racquet face, it spends the critical part of the stroke always facing the target.

The beauty of this is the motion dependent effect upon the wrist joint. If you keep a relaxed wrist, it will naturally lag behind (i.e. wrist joint will naturally extend).

Perhaps this is all common sense to many, but it was a bit of a revelation to me.

Makes sense to me. regardless of whether we're talking about a racquet, golf club, baseball bat, etc. They should all be swung on a inside-out path up to contact, and then back outside-in post contact.(conservation of angular momentum) In the case of tennis, the extended wrist allows for the raquet face to "square up" to the line of the ball.

Legend
I'll try to make an animation or a graphic when I get home.

no need to go to that trouble for me. i already get it.

pushing_wins

Hall of Fame
KM recommends a completely different type of stroke, where the hips remain closed throughout the entire stroke.

I'm referring more to the standard open stance forehand.

a standard open hand forehand closes as you swing forward.

given that, we are back at the hip thing.

reconcilling factor is more the hip than the wrist. this is km's theory

pushing_wins

Hall of Fame
Makes sense to me. regardless of whether we're talking about a racquet, golf club, baseball bat, etc. They should all be swung on a inside-out path up to contact, and then back outside-in post contact.(conservation of angular momentum) In the case of tennis, the extended wrist allows for the raquet face to "square up" to the line of the ball.

inside out, hitting against a strong left side.

this is consistent with km's closed hips

spacediver

Hall of Fame
a standard open hand forehand closes as you swing forward.

given that, we are back at the hip thing.

reconcilling factor is more the hip than the wrist. this is km's theory

I'm not following. When you say the forehand "closes", what are you referring to?

pushing_wins

Hall of Fame
I'm not following. When you say the forehand "closes", what are you referring to?

lower body counterbalance

u didnt pay any attention to what i said before

lol

spacediver

Hall of Fame
Sorry man, I'm completely lost with what you're trying to say here. Can you flesh out your ideas a bit more thoroughly? I feel like I'm talking to a stoned yoda here

pushing_wins

Hall of Fame
can u ask km for a copy of his articule on tennisplayer.net? the one about true alignment on a forehand. thats explains his closed hip theory.

spacediver

Hall of Fame
can u ask km for a copy of his articule on tennisplayer.net? the one about true alignment on a forehand. thats explains his closed hip theory.

I'm a member, and have read almost all his articles. I found the true alignment interesting, but what is lacking is a proper analysis of why true alignment is causally important to producing a good stroke.

I think one of the reasons that you often see a straight line between back foot, front foot, and target (during contact) is because the back leg is kicking back in countermomentum to prevent the body from over rotating (kinda like the non dominant hand swings back to prevent over-rotating in the 1hbh).

Furthermore, one can have the hips open to the target while still having the legs in a scissor position.

There's very little biomechanical analysis in that article - the real legitimate point I take from it is that over-rotating the hips is bad (although this is a VERY different prescription from "keep the hips closed").

Finally, I'm not sure what this discussion has to do with the issue of linear vs. angular momentum (which is what this thread is about). Are you getting at the idea that with closed hips you can swing the racquet like a golf club and have it not curve at all around the plane parallel to the ground?

pushing_wins

Hall of Fame
maybe we are misunderstanding each other

maybe u have already considered all the points i m trying to make

spacediver

Hall of Fame
maybe we are misunderstanding each other

maybe u have already considered all the points i m trying to make

I was trying to share a solution to the problem of hitting through the ball while spinning around.

Often we hear in instruction that we should hit through the ball, yet we should rotate on follow through. Many students may feel this presents a problem:

In order to change from a straight path to a curved path, it seems natural that you need to exert a muscular force to effect this change (else the follow through would be like a one arm windmill, as if someone were bowling a cricket ball in reverse).

My post was to show how one can achieve this change from a more-or-less straight path into a curved path but without having to consciously change the direction of the racquet.

pushing_wins

Hall of Fame
I was trying to share a solution to the problem of hitting through the ball while spinning around.

Often we hear in instruction that we should hit through the ball, yet we should rotate on follow through. Many students may feel this presents a problem:

In order to change from a straight path to a curved path, it seems natural that you need to exert a muscular force to effect this change (else the follow through would be like a one arm windmill, as if someone were bowling a cricket ball in reverse).

My post was to show how one can achieve this change from a more-or-less straight path into a curved path but without having to consciously change the direction of the racquet.

ok it was a misunderstanding on my part

my issue has always been, how to change a circular path to a straight then back to a circular.

spacediver

Hall of Fame
there is a concensus around here that the wrist layback is passive

yes, and a passively laid back wrist is precisely what I'm talking about. Read the original post carefully.

The beauty of this is the motion dependent effect upon the wrist joint. If you keep a relaxed wrist, it will naturally lag behind (i.e. wrist joint will naturally extend).

pushing_wins

Hall of Fame
yes, and a passively laid back wrist is precisely what I'm talking about. Read the original post carefully.

however, the wrist is not the reconciling factor

spacediver

Hall of Fame
again, you're repeating yourself. I've tried to show how it can be a reconciling factor.

If you disagree, then break down my analysis and present an alternative.

pushing_wins

Hall of Fame
again, you're repeating yourself. I've tried to show how it can be a reconciling factor.

If you disagree, then break down my analysis and present an alternative.

withour breaking down your analysis - thats the hard way

there is one reconciling factor
the reconciling factor is the use of the lower body
hence, the wrist is not the reconciling factor

to backup my argument for use of the lower body, i refer to km's true alignment article

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spacediver

Hall of Fame
It's fine to just state that the lower body is the reconciling factor, but you need to show how!

I've taken the effort to articulate the emergent geometry when you have an interaction between the wrist and the arm, and it makes mathematical sense.

You need to be more specific - you're not making any sense at all.

Let me try to help: Are you suggesting that with closed hips, you can swing the racquet like a golf club?

btw to illustrate the sort of geometry I'm talking about, look at the 4:45 mark in this video:

It's not quite how I describe - in the video, the wrist is already laid back well before contact. In my description, the wrist is in the process of being laid back through contact.

pushing_wins

Hall of Fame
ok, i concede for the moment

r u down for a hit with davimarat and i?

Spokewench

Semi-Pro
Just Glad I don't worry about what reconciles what when I hit a tennis ball

If I even tried to think about what reconciles what when I'm hitting a tennis ball, it would be Whiff, Whiff Whiff one after another.

Who can think that much and get your body to do what it is supposed to do. Just let the body figure it out!

gameboy

Hall of Fame
You have to remember that human body is not just simply rotating during the swing. There are significant lag between legs, hips, torso, shoulder, arm, and wrist. All firing at different times, which will result in a lot of linear motion. Your body is also moving forward during the swing so there is significant linear motion there as well.

The thought of driving through the ball is nothing more than a tool to help you coordinate your linear motion with angular motion.

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5263

G.O.A.T.
Check out the MTM Fh. Sounds like you are discovering some of it.

spacediver

Hall of Fame
ok, i concede for the moment

r u down for a hit with davimarat and i?

yea would love to man - pretty flexible over the next few days

spacediver

Hall of Fame
If I even tried to think about what reconciles what when I'm hitting a tennis ball, it would be Whiff, Whiff Whiff one after another.

Who can think that much and get your body to do what it is supposed to do. Just let the body figure it out!

I am wary of paralysis by analysis. But there is a time for analysis. I find having solid biomechanical models in mind that I can trust allows me to guide my learning effectively. It's been crucial for my serve development.

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spacediver

Hall of Fame
You have to remember that human body is not just simplay rotating during the swing. There are significant lag between legs, hips, torso, shoulder, arm, and wrist. All firing at different times, which will result in a lot of linear motion.

Yes this certainly complicates the issue. Admittedly, my example is a very simple one, but it is a useful model that illustrates how the wrist can play a role in modulating the linearity of the stroke.

Your other points are well taken.

Dreamer

Professional
Lol space. you are too cute.

And very astute. Many players both good and bad don't understand this concept. However I think there is merit on knowing why ^^

pushing_wins

Hall of Fame

how do mometum translate into hitting the ball harder? what is the physics behind that?

what is the objective? hit the ball harder?

spacediver

Hall of Fame
pushing, I think you're entirely misunderstanding this thread. I'm purely interested in exploring the geometry of the stroke. I'm presenting one possible solution to the puzzle of incorporating both linear and angular momentum into the forehand.

I'm not suggesting that this is the only way to do it.

I'm not even suggesting that linear momentum is necessary in all forehands.

btw, after watching John Yandell's latest high speed of federer (the latest music video), I realize that my analysis doesn't describe all forehands. Federer's wrist joint acts like the end of a whip during his forehand. It doesn't stay laid back during the stroke.

dreamer: thanks for the kind words

pushing_wins

Hall of Fame
pushing, I think you're entirely misunderstanding this thread. I'm purely interested in exploring the geometry of the stroke. I'm presenting one possible solution to the puzzle of incorporating both linear and angular momentum into the forehand.

I'm not suggesting that this is the only way to do it.

I'm not even suggesting that linear momentum is necessary in all forehands.

btw, after watching John Yandell's latest high speed of federer (the latest music video), I realize that my analysis doesn't describe all forehands. Federer's wrist joint acts like the end of a whip during his forehand. It doesn't stay laid back during the stroke.

dreamer: thanks for the kind words

sorry, that was an off-topic question

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