Move Forward In Tennis And Don't Change A Thing

Curious

G.O.A.T.
Yeah, nothing he said is based in physics.

But there should be an explanation as to why weight transfer is widely used in sports as @S&V-not_dead_yet mentioned before.
Is the benefit somewhere else if it’s not the added racket head speed? Maybe.



I look at it from the viewpoint of other sports:
- Baseball batters move forward as they are about to hit
- Baseball pitches move forward as they are about to pitch
- Baseball fielders move forward as they are about to throw
- Football QBs do likewise when they want to throw a long pass
- Javelin throwers take a running start
- Boxers use their body when throwing a punch
All of these are examples of weight transfer as I understand the term to mean. If weight transfer were a myth, none of these examples would be so consistent.
 

fecund345

Rookie
Works only when the body acts as a rigid body, more or less. It is a principle in mechanics that a rigid body will maintain the direction of a force applied to it. In other words, if a force is applied on the north pole of a rigid sphere vertically down, it will be transmitted to the south pole vertically, and for something attached to the south pole, the force will appear to vertically emerge downwards from there. It is called the principle of transmissibility of force.

In a non rigid body with different parts attached to it loosely through different kinds of joints, this is not true. That is why an effective mass is calculated.

Take an extreme example. A fat man and a thin man are both given a balloon attached to a string which they hold like a pendulum. If both of them run and swing the balloon at a wall,, do you think the fat man will necessarily hit the wall harder with the ballon?

Here the additional mass contributed to the balloon by the body is probably almost 0.
No one is adding mass...it is all about momentum being transferred

Sent from my SM-A102U using Tapatalk
 

Curious

G.O.A.T.
How about tossing the ball further into court for higher pace?
I clearly feel it’s faster that way although haven’t confirmed objectively.
 

fecund345

Rookie
Your videos are demonstrating that adding lead to the racket will increase the speed of the ball which is true if the racket is moving at the same speed as the unleaded racket. It would also require more force to get the racket to the same speed. If you applied that increased force to a lighter racket it would make it go faster which would also increase the speed of the ball.

So physics is saying that to hit a ball harder you have to hit the ball harder.
No!!! It says that a larger mass' momentum speeds up a smaller mass

Sent from my SM-A102U using Tapatalk
 

fecund345

Rookie
My body mass is transferred as acceleration into the tennis balll... my legs are accelerating my torso which accelerates my arm which explodes into the ball

Sent from my SM-A102U using Tapatalk
 

user92626

G.O.A.T.
In other words, if a force is applied on the north pole of a rigid sphere vertically down, it will be transmitted to the south pole vertically, and for something attached to the south pole, the force will appear to vertically emerge downwards from there. It is called the principle of transmissibility of force.

Are you saying things come into one end (the north) will come out the other end (the south)? And the transmissibility requires force? Yeah I'm familiar with that principle.
 

fecund345

Rookie
Serves and groundstrokes involves momentum transfers like the whip illustration below:

When swung, the hand moves slowly under twenty miles per hour. A traveling wave moves into the "thick" part, and travels toward the "thin" part. The wave speeds up, because there is less mass to carry the same energy. When the wave reaches the tip, it is a tiny, mass moving faster than sound.

Sent from my SM-A102U using Tapatalk
 

Knox

Semi-Pro
My body mass is transferred as acceleration into the tennis balll... my legs are accelerating my torso which accelerates my arm which explodes into the ball

Sent from my SM-A102U using Tapatalk

Wait... what?

Your mass is transferred as acceleration?

How does mass get converted to acceleration?

I think you're correct about the sequence of acceleration assists... hips rotate, shoulders rotate, arm pulls hand across.

Where you seem to be running into trouble is with this talk about weight/momentum transfer.

Moving forward as you hit doesn't add mass to the system in a tennis swing. It may add velocity/acceleration, but we've already figured out much better ways of doing that.
 

Knox

Semi-Pro
No one is adding mass...it is all about momentum being transferred

Sent from my SM-A102U using Tapatalk

Momentum is mass multiplied by velocity.

The only relevant mass is that of the racquet and perhaps your forearm as sureshs is suggesting.

Momentum from your body mass doesn't get transferred to the ball in a tennis swing.
 

Knox

Semi-Pro
I weigh 290 lbs and let's say you weigh 150 lbs. You run at me at 15 miles per hour. I run at you at 10 miles per hour. Who will wound up on their a*$ after we collide?
I think more of my momentum will be transferred into you as backward acceleration because of my larger mass.

Sent from my SM-A102U using Tapatalk

Yes, that's correct, but that's not the type of collision we're dealing with when we're talking about tennis swings.

Racquet mass and velocity is what's relevant. Body mass and velocity is irrelevant.
 

Knox

Semi-Pro
Serves and groundstrokes involves momentum transfers like the whip illustration below:

When swung, the hand moves slowly under twenty miles per hour. A traveling wave moves into the "thick" part, and travels toward the "thin" part. The wave speeds up, because there is less mass to carry the same energy. When the wave reaches the tip, it is a tiny, mass moving faster than sound.

Sent from my SM-A102U using Tapatalk

Whip cracking has more to do with conservation of angular momentum.

It's similar to that trick you can do in an office chair to make yourself spin really fast. You know which one I'm talking about?
 

fecund345

Rookie
Whip cracking has more to do with conservation of angular momentum.

It's similar to that trick you can do in an office chair to make yourself spin really fast. You know which one I'm talking about?
Nope educate me

Sent from my SM-A102U using Tapatalk
 

Curious

G.O.A.T.
Yes, that's correct, but that's not the type of collision we're dealing with when we're talking about tennis swings.

Racquet mass and velocity is what's relevant. Body mass and velocity is irrelevant.
Let’s complicate it even more:)
I was talking to a friend about this weight transfer thing and he said even though the acceleration in modern tennis comes from angular momentum, a heavier guy’s weight will still cause more of that! Bigger mass bigger torque sort of thing:D
 

fecund345

Rookie
Let’s complicate it even more:)
I was talking to a friend about this weight transfer thing and he said even though the acceleration in modern tennis comes from angular momentum, a heavier guy’s weight will still cause more of that! Bigger mass bigger torque sort of thing:D
That's what I have sayin..momentum transfer

Sent from my SM-A102U using Tapatalk
 

Curious

G.O.A.T.
That's what I have sayin..momentum transfer

Sent from my SM-A102U using Tapatalk
But it’s the rotation of torso in the long axis. Can that be considered as weight transfer?Besides I thought you were talking about linear weight transfer.
 

travlerajm

Talk Tennis Guru
Take an extreme example. A fat man and a thin man are both given a balloon attached to a string which they hold like a pendulum. If both of them run and swing the balloon at a wall,, do you think the fat man will necessarily hit the wall harder with the ballon?
I have witnessed your power first hand. The answer is clear.
 

Knox

Semi-Pro
Let’s complicate it even more:)
I was talking to a friend about this weight transfer thing and he said even though the acceleration in modern tennis comes from angular momentum, a heavier guy’s weight will still cause more of that! Bigger mass bigger torque sort of thing:D

Heavier racquet, yeah.

Heavier belly? Nah.
 

fecund345

Rookie
I give up.
.you are right...I am wrong...nothing I said in this thread is true

Sent from my SM-A102U using Tapatalk
 

fecund345

Rookie
Excuse my profound ignorance about physics...you guys were right on the money and you have successfully exposed me as the fraud I am

Sent from my SM-A102U using Tapatalk
 

RajS

Semi-Pro
@fecund345 I think your physics is fine. I agree the purpose of "weight transfer" or "weight shift" is to ultimately increase racket head speed. As I understand it, you push with one leg and shift (or transfer) your weight to the other leg, and in the process generate momentum, some of which transfers to the racket through the interconnected system of levers that the human body is. The whip analogy works for me.

The question of how much weight to have behind the racket is a tricky one. For a given racket head speed, I think increasing weight has diminishing returns. The amount of momentum that can be transferred to the ball, as a function of racket weight, has a limit that is speed dependent, so even if the racket weighs a ton, you won't be able to launch the ball to the moon with normal swing speeds (assuming you can swing such a racket!). Thus, a very heavy person who generates only normal swing speeds should have no great advantage in generating ball speed, even if you assume his weight adds to the so called effective weight of the racket.
 

fecund345

Rookie
@fecund345 I think your physics is fine. I agree the purpose of "weight transfer" or "weight shift" is to ultimately increase racket head speed. As I understand it, you push with one leg and shift (or transfer) your weight to the other leg, and in the process generate momentum, some of which transfers to the racket through the interconnected system of levers that the human body is. The whip analogy works for me.

The question of how much weight to have behind the racket is a tricky one. For a given racket head speed, I think increasing weight has diminishing returns. The amount of momentum that can be transferred to the ball, as a function of racket weight, has a limit that is speed dependent, so even if the racket weighs a ton, you won't be able to launch the ball to the moon with normal swing speeds (assuming you can swing such a racket!). Thus, a very heavy person who generates only normal swing speeds should have no great advantage in generating ball speed, even if you assume his weight adds to the so called effective weight of the racket.
I never advocated for a heavier racket, it was all these Rhode Scholar experts that perpetrated that. I just tried to indicate that larger mass scan transfer momentum to a smaller mass. None o them addresed the linear momentum shift...they acted like I was advocating linear momentum over angular momentum...I just trying to say that your normal stroke coupled with moving forward leads to more power.. but alas these experts have decided without trying out that I am full of it..so I guess I am full of it.. I am tired of hearing world is flat

Sent from my SM-A102U using Tapatalk
 

Knox

Semi-Pro
I never advocated for a heavier racket, it was all these Rhode Scholar experts that perpetrated that. I just tried to indicate that larger mass scan transfer momentum to a smaller mass. None o them addresed the linear momentum shift...they acted like I was advocating linear momentum over angular momentum...I just trying to say that your normal stroke coupled with moving forward leads to more power.. but alas these experts have decided without trying out that I am full of it..so I guess I am full of it.. I am tired of hearing world is flat

Sent from my SM-A102U using Tapatalk

When you say that moving forward leads to more power, and suggest that there is a 'linear momentum shift' then you ARE advocating linear momentum over angular momentum.

If we agree that tennis groundstrokes are angular (which they are) then how do you propose moving into the ball LINEARLY increases power? You say there's a linear momentum shift... yet all the top experts on modern stroke technique disagree, and the basic math disagrees as well. It's already been repeatedly established by tennis researchers that open stance rotationally driven swinging is the superior method of generating power on the forehand. I assume you're familiar with this research.

So, if you're familiar with how the open stance generates angular momentum then how do you propose one modifies it to be compatible with moving linearly towards the ball? Moving forward into the shot is totally at odds with the fundamentals of using open stance. I'm curious how you reconcile this incompatibility.
 
Last edited:
The body is part of the kinetic chain. Besides, we all know it is much harder it is getting sufficient power into a BH when stepping backwards. But rotating and stepping forward are to different ways for the body to contribute to the kinetic chain or momentum.
 

Kevo

Legend
Racquet mass and velocity is what's relevant. Body mass and velocity is irrelevant.

I think you are ignoring effective mass. If a child holds a racquet still and we hit it with a tennis ball at 60mph you seem to be claiming that the result will be the same as a full grown man holding that same racquet with the ball impacting at 60mph.

You could fairly easily create an experiment with some clamps and weight plates if you want to study this. I think the result will not be the same. I think the ball will come back with more velocity after adding an additional 100lbs to the apparatus. I don't think you can entirely discount the addition of mass to the body holding the racquet.

You could also try the same thing with adding mass to the racquet itself and determine how much more effective it is to have the additional mass on the racquet, and I think that would be interesting as well. I would suspect that putting a much smaller amount of mass on the frame would be equivalent to a larger mass on the body, but I would need to be convinced that the body doesn't matter.
 

Kevo

Legend
So, if you're familiar with how the open stance generates angular momentum then how do you propose one modifies it to be compatible with moving linearly towards the ball? Moving forward into the shot is totally at odds with the fundamentals of using open stance. I'm curious how you reconcile this incompatibility.

An open stance forehand uses weight transfer as well, just in a different way. You shift your weight from one foot to the other as you rotate. Shifting your center of mass (gravity) is a super common theme in sports.
 

ChaelAZ

G.O.A.T.
Does anyone have the research links of the kinetics and biomechanics that demonstrate weight transfer force does not increase KE impact on the ball? I've never come across any so would be an interesting read.
 

Kevo

Legend
Does anyone have the research links of the kinetics and biomechanics that demonstrate weight transfer force does not increase KE impact on the ball? I've never come across any so would be an interesting read.

Sit in a rolling swivel chair and then hit a tennis ball. That would not be very effective. There has to be an equal and opposite force according to Newton's laws. A mass in motion has a force that can be pushed against assuming it's moving in a useful direction. There is certainly a question of how effective that extra mass will be in practice, but to say it doesn't matter at all seems obviously wrong to me.
 

sureshs

Bionic Poster
Two issues are being confused here:

Weight transfer into the ball during a stroke
and
Moving towards the ball and taking it early

They are different things. Agassi took balls early by standing close to the baseline. When he hit the ball, he transferred weight into it and used the kinetic chain to generate momentum rather than arming it. Nadal stays back and takes the ball later, but when he hits the ball he transfers weight into it.
 

BallBag

Professional
You cant transfer weight or momentum into a ball. The only way to make the ball go faster is by hitting it harder. Weight transfer and kinetic chain are complicated ideas that can not be explained with first year physics concepts. You can apply some concepts in very limited ways that are not useful in explaining why none of us hit the ball as hard as Nadal.
 

Knox

Semi-Pro
I think you are ignoring effective mass. If a child holds a racquet still and we hit it with a tennis ball at 60mph you seem to be claiming that the result will be the same as a full grown man holding that same racquet with the ball impacting at 60mph.

You could fairly easily create an experiment with some clamps and weight plates if you want to study this. I think the result will not be the same. I think the ball will come back with more velocity after adding an additional 100lbs to the apparatus. I don't think you can entirely discount the addition of mass to the body holding the racquet.

You could also try the same thing with adding mass to the racquet itself and determine how much more effective it is to have the additional mass on the racquet, and I think that would be interesting as well. I would suspect that putting a much smaller amount of mass on the frame would be equivalent to a larger mass on the body, but I would need to be convinced that the body doesn't matter.


You're conflating effective mass with structural rigidity.

I'm not claiming the child would have the same result as the grown man.

The grown man is stronger and therefore has more structural rigidity, so of course the results would be different. However, once the child gets strong enough to have sufficient structural rigidity then I do think that they could have the same result as a grown man.
 

Knox

Semi-Pro
An open stance forehand uses weight transfer as well, just in a different way. You shift your weight from one foot to the other as you rotate. Shifting your center of mass (gravity) is a super common theme in sports.



The weight transfer in open stance is weight being transferred from one foot to another in conjunction with the angular momentum generating hip rotation.

OP is suggesting a forward weight transfer where weight is transferred from the body and into the ball. That's not physically possible. Momentum transfer doesn't happen that way in tennis strokes.

So yes, the open stance does use weight transfer in a different way. And by 'different way' I mean a way that actually works.
 

Knox

Semi-Pro
Does anyone have the research links of the kinetics and biomechanics that demonstrate weight transfer force does not increase KE impact on the ball? I've never come across any so would be an interesting read.

I would start by looking at how force is generated in standard open stance groundstrokes. Then, see how your findings there are compatible with the idea of moving forward as you hit to increase power.

I think you'll find that open stance and moving forward into the ball are incompatible methods.
 

BallBag

Professional
You're conflating effective mass with structural rigidity.

I'm not claiming the child would have the same result as the grown man.

The grown man is stronger and therefore has more structural rigidity, so of course the results would be different. However, once the child gets strong enough to have sufficient structural rigidity then I do think that they could have the same result as a grown man.

The child would have the same result as a grown man as long as both got the racket to the same speed.


Also notice how the PHD that wrote that is not saying anything about momentum.
 

Knox

Semi-Pro
The child would have the same result as a grown man as long as both got the racket to the same speed.


Also notice how the PHD that wrote that is not saying anything about momentum.

Kevo's scenario said if the child was holding the racquet still.

Do you think that they'd still have the same resulting speed?

Now that I think about it, I think they might, however I think the child's racquet might be deflected more than the adults due to the structural rigidity thing I mentioned.

edit: my hunch is corroborated by the experiment conclusions:

"The theoretical consensus is that the ball leaves the strings before it receives any information from the handle on whether it is hand-held or free. We test that here.

...

The generalized conclusion is that there is essentially no difference in ACOR between the free-standing and hand-held condition"

Nice post BallBag
 

BallBag

Professional
Kevo's scenario said if the child was holding the racquet still.

Do you think that they'd still have the same resulting speed?

Now that I think about it, I think they might, however I think the child's racquet might be deflected more than the adults due to the structural rigidity thing I mentioned.

edit: my hunch is corroborated by the experiment conclusions: "The generalized conclusion is that there is essentially no difference in ACOR between the free-standing and hand-held condition"

Nice post BallBag
That experiment is with stationary racket so yeah. The racket would deflect more in the child's hand but the ball don't care, he gone.
 

ChaelAZ

G.O.A.T.
Sit in a rolling swivel chair and then hit a tennis ball. That would not be very effective. There has to be an equal and opposite force according to Newton's laws. A mass in motion has a force that can be pushed against assuming it's moving in a useful direction. There is certainly a question of how effective that extra mass will be in practice, but to say it doesn't matter at all seems obviously wrong to me.
I would start by looking at how force is generated in standard open stance ground strokes. Then, see how your findings there are compatible with the idea of moving forward as you hit to increase power.

I think you'll find that open stance and moving forward into the ball are incompatible methods.

The way I see it or understand it, force is generated different ways during strokes, and one isn't exclusive. Any method to generate that force - rotation, linear velocity (why you can have your body moving backward and still hit forward), pushing off the ground (the opposing force) - will all move the racquet and counteract the direction of the ball, and all are used depending on the situation. As far as the term weight transfer, I think it is being seen as a massive push into the ball, but again my understanding is it is part of the mechanics from pushing from the ground, but more as part of the balance of the body during the transfer of of force. The natural result is movement towards the ball, so maybe a small step. But it isn't this huge movement of you body mass forward all the time. That step back an into the ball is simply positioning for balance.

So basically I learned about weight transfer as part of the stance balance mechanics. If weight transfer way using work to move your body weight into a ball for added force I would think it would completely throw things off for balance, and certainly recovery.
 

fecund345

Rookie
When you say that moving forward leads to more power, and suggest that there is a 'linear momentum shift' then you ARE advocating linear momentum over angular momentum.

If we agree that tennis groundstrokes are angular (which they are) then how do you propose moving into the ball LINEARLY increases power? You say there's a linear momentum shift... yet all the top experts on modern stroke technique disagree, and the basic math disagrees as well. It's already been repeatedly established by tennis researchers that open stance rotationally driven swinging is the superior method of generating power on the forehand. I assume you're familiar with this research.

So, if you're familiar with how the open stance generates angular momentum then how do you propose one modifies it to be compatible with moving linearly towards the ball? Moving forward into the shot is totally at odds with the fundamentals of using open stance. I'm curious how you reconcile this incompatibility.
I agree with superiority of the modern forehand stroke and its angular momentum basis...two options...would have to try an anticipated the bounce in order to hit most balls on the rise...extremely difficult to do with this stroke...or use flatspin which requires less setup time...but would still require hitting on the rise on most ball to incorporate any linear momentum advantages....I know easier said than done...but I am not calling for any angular momentum minimization or eliminations...that is where 85 % of the power would be generated

Sent from my SM-A102U using Tapatalk
 

Kevo

Legend
The weight transfer in open stance is weight being transferred from one foot to another in conjunction with the angular momentum generating hip rotation.

OP is suggesting a forward weight transfer where weight is transferred from the body and into the ball. That's not physically possible. Momentum transfer doesn't happen that way in tennis strokes.

So yes, the open stance does use weight transfer in a different way. And by 'different way' I mean a way that actually works.

Obviously weight can't transfer from one object to another. But mass moving forward and colliding with another mass can transfer energy. Obviously mass matters. It seems the question is if the mass of the person holding a racquet has any effect on the collision of the racquet and ball. I contend that it does. The next question is how. My contention is that you can't divorce that mass completely from the swing. I would imagine that the effect is small in most cases, but I don't think the effect is zero. The problem might be teasing out the magnitude of the effect, and I'm not sure how you would go about that to everyone's satisfaction since there is no way that I know of to ensure consistency using actual people, but I proposed one method which I think makes sense but you dismissed it as measuring structural rigidity. I think if the apparatus is the same and only the mass is different then it should work, since structural rigidity would be the same just with more mass.

If we're talking about weight transfer being a working way in an open stance, then it should also be used in a working way in a closed stance forehand. Maybe the definition of the problem has changed some how in this thread, but I don't think you'll find any coach that doesn't believe using your weight properly is beneficial. I've heard it all my life and lived it in all the sports I participated in. Baseball, football, tennis, skateboarding, bicycling, and gymnastics all use weight transfer to make gravity work for us as much as possible.
 
When you are pulling the racket forward, the mass of the racket is connected to the mass of the body. Just like the tip of the whip is connected to the opposite thicker, heavier end. If you cut of some of the heavier end of the whip, you do not get the same effect.
Same if you imagined a tennis player with legs and arms, but no torso (yikes...).
 

Kevo

Legend
That experiment is with stationary racket so yeah. The racket would deflect more in the child's hand but the ball don't care, he gone.

Now what happens if they are moving forward, i.e. "transferring their weight" into the shot?

What about hitting volleys with your legs instead of swinging? These are all things where we tell our students to get their body into the shot. Some of these "such and such is a myth" threads are based on some misunderstanding of what the advice is for.
 
Top