confused w/ the term "MTM"

[sureshs]

Originally Posted by toly

In general, IMO, our body just cannot create very fast straight linear motions. That’s why, Federer and Nadal rotates straight arm before impact. I didn’t see any pro that can use straight linear motion before and during impact. Maybe you can provide some videos?

I don't think they can. All they seem to do is to manage to get the racket face perpendicular to the ball trajectory at impact and control the curvature to some extent, so as to meet the trajectory smoothly (as I had said before). You seem to think of linear as parallel to the sidelines. I think of it more as a measure of local curvature of the arc at impact (what you would know as reciprocal of the second derivative).

[5263]

Originally Posted by toly

In general, IMO, our body just cannot create very fast straight linear motions. That’s why, Federer and Nadal rotates straight arm before impact. I didn’t see any pro that can use straight linear motion before and during impact. Maybe you can provide some videos that support hitting through idea?

I think you are making some very good points here. Even if there are math terms
that account for the arc motions of the body in a linear result, that still does
not change that the actual motion was an arc.

[bhupaes]

Originally Posted by toly

I don’t like a vague tennis terminology. It seems that nobody is able to explain clearly what exactly we should do to extend through the ball. Our joints are very good with rotational movement, but very bad with straight linear motion. IMO, we just have to rotate relevant parts of the body in synchronized manner and forget about across or through aspects.

Agree with 5263, this is a good post, toly. And don't write off the picture sequence of Serena you posted above as being all flat and having no topspin. It is not evident from the picture, but her hand is pulling in, causing the racquet to whip into the ball, and it definitely has an upwards movement (can't anything tell about sidespin, though). That plus the forward tilt of the racquet will ensure there is a lot of topspin, probably much more than I can hit! But the trajectory of the ball looks like it will be flat.

Thanks for posting this great pic.

[toly]

Originally Posted by sureshs

I don't think they can. All they seem to do is to manage to get the racket face perpendicular to the ball trajectory at impact and control the curvature to some extent, so as to meet the trajectory smoothly (as I had said before). You seem to think of linear as parallel to the sidelines. I think of it more as a measure of local curvature of the arc at impact (what you would know as reciprocal of the second derivative).

It is absolutely obvious that in order to hit through 5 bolls the racquet should move along a straight line at least 10’’ with stable racquet face orientation. “Piston stroke” can provide this, but you don’t want to utilize it because it is slow motion. Then, you should think about approximation of the straight line.

Radius of Osculating circle of the straight line is infinity. Thus, if you use rotational motion only, you have to increase radius of rotation as much as possible. From this point of view, straight arm FH is probably the best, because that creates maximum radius. However, most pros use bend elbow FH. So, they don’t care about hitting through.

If you know some different but particular way to “control the curvature to some extent, so as to meet the trajectory smoothly”, just let me know please.

[toly]

Originally Posted by bhupaes

Agree with 5263, this is a good post, toly. And don't write off the picture sequence of Serena you posted above as being all flat and having no topspin. It is not evident from the picture, but her hand is pulling in, causing the racquet to whip into the ball, and it definitely has an upwards movement (can't anything tell about sidespin, though). That plus the forward tilt of the racquet will ensure there is a lot of topspin, probably much more than I can hit! But the trajectory of the ball looks like it will be flat.

Thanks for posting this great pic.

Thanks for comments.

Serena uses very actively ISR before and during impact, but smoothly. I don’t see any abrupt sideways acceleration and it is practically impossible. She really pulls in because ISR stands for Internal Shoulder Rotation.

[bhupaes]

Originally Posted by toly

Thanks for comments.
Serena uses very actively ISR before and during impact but smoothly. I don’t see any abrupt sideway acceleration and it is practically impossible. She really pulls in because of ISR, but it has nothing to do with Wegner description of modern FH.

I think Serena uses a combination of ISR and biceps, pretty late in the stroke (close to contact), hence one might say it's abrupt. But that doesn't really matter. In answer to your question on how to create a linear stroke, notice how the path of the racquet head is pretty much linear for most of the stroke. It becomes circular close to contact due to her ISR and biceps action. Now ask yourself, if the ideal stroke is totally linear, why should Serena change a good thing (linear motion) into a bad thing (motion in an arc), and so close to contact at that? Could it be because the act of pulling in the racquet increases RHS both forwards and upwards?!

[arche3]

Originally Posted by bhupaes

I think Serena uses a combination of ISR and biceps, pretty late in the stroke (close to contact), hence one might say it's abrupt. But that doesn't really matter. In answer to your question on how to create a linear stroke, notice how the path of the racquet head is pretty much linear for most of the stroke. It becomes circular close to contact due to her ISR and biceps action. Now ask yourself, if the ideal stroke is totally linear, why should Serena change a good thing (linear motion) into a bad thing (motion in an arc), and so close to contact at that? Could it be because the act of pulling in the racquet increases RHS both forwards and upwards?!

I think Serena and other pros pull the bicep and use internal rotation of the shoulders to whip the head of the racket at contact. It seems a normal part of the modern type stroke. If you watch old era guys with wood rackets they don't really do this. Its like the serve really. In the serve you serve up so the hand will slow down as the racket whips through the serve. The conti grip and pronation on serve allows this. The fh now follows similar principles of the whip applied in a different way.

[bhupaes]

Originally Posted by arche3

I think Serena and other pros pull the bicep and use internal rotation of the shoulders to whip the head of the racket at contact. It seems a normal part of the modern type stroke. If you watch old era guys with wood rackets they don't really do this. Its like the serve really. In the serve you serve up so the hand will slow down as the racket whips through the serve. The conti grip and pronation on serve allows this. The fh now follows similar principles of the whip applied in a different way.

Agreed. I haven't studied the pros who wielded wooden racquets much... but I am sure some were very modern - like Bjorn Borg, for instance!

[bhupaes]

Also, note that it's not all about power - the goal is not to send the tennis ball after the Mars Rover! IMO, tennis strokes have evolved in such a way so as to enable the player to increase pace and control proportionally. The pulling in motion which incorporates both "up" and "across" increases linear pace as well as spin control, as it should.

[arche3]

Originally Posted by bhupaes

Agreed. I haven't studied the pros who wielded wooden racquets much... but I am sure some were very modern - like Bjorn Borg, for instance!

Yeah I saw old videos of Borg hitting the Nada fh.

[LeeD]

I"m pretty sure EllworthVines used a modern forehand from waist up, not using nearly as much legs. His finishes were well past his left shoulder.

[sureshs]

Originally Posted by toly

It is absolutely obvious that in order to hit through 5 bolls the racquet should move along a straight line at least 10’’ with stable racquet face orientation. “Piston stroke” can provide this, but you don’t want to utilize it because it is slow motion. Then, you should think about approximation of the strait line.

Osculating circle of the straight line is infinity. Thus, if you use rotational motion only, you have to increase radius of rotation as much as possible. From this point of view, straight arm FH is probably the best, because that creates maximum radius. However, most pros use bend elbow FH. So, they don’t care about hitting through.

If you know some different but particular way to “control the curvature to some extent, so as to meet the trajectory smoothly”, just let me know please.

The particular way is the intuition of the pros. Just like it is meaningless to ask how Nadal produces a curved trajectory of the ball thinking that he uses mathematics for it.

As far as hitting 5 balls in a row, OK that may not be 5, it may be say 3.

Here is a simple calculation. TW University uses a racket tip speed at impact of 80 mph for ATP forehands. You can do a calculation of how much the tip will travel in a 4 ms dwell time, and it comes out to be 5.7 inches, or 2.2 ball diameters. Add in the fact that for a little more time the racquet will be maintaining its inertia after the ball leaves, and 3 balls in a row is not unimaginable.

Does it mean that the pro guides his racket in a straight line towards the target? No. It just means that he makes solid contact towards the intended direction as part of his up, forward and leftward trajectory of the swing.

I have said many times that topspin cannot be produced by purely rigid bodies. There has to be deformation in a certain dwell time. If you meet the ball in a certain way, it will be deformed and released in such a way that it will have both forward momentum and spin. If you don't meet it solidly, it won't have much pace but will have spin from a grazing motion. The solid meeting is what is commonly called hitting through the ball, and also produces the "pro sound" on impact. The reason it is emphasized is that club players often hit tentatively.

[toly]

Originally Posted by bhupaes

I think Serena uses a combination of ISR and biceps, pretty late in the stroke (close to contact), hence one might say it's abrupt. But that doesn't really matter. In answer to your question on how to create a linear stroke, notice how the path of the racquet head is pretty much linear for most of the stroke. It becomes circular close to contact due to her ISR and biceps action. Now ask yourself, if the ideal stroke is totally linear, why should Serena change a good thing (linear motion) into a bad thing (motion in an arc), and so close to contact at that? Could it be because the act of pulling in the racquet increases RHS both forwards and upwards?!

I think that Serena doesn’t use right arm bicep significantly, because she doesn’t bend additionally her elbow around and after impact. See picture below.



About straight linear motion: She applies bend elbow FH technique, because she can use ISR, the fastest motion of the arm, to build translational motion of the ball. In case of straight arm ISR can create spin and practically zero translational speed. That’s why almost all WTA players use bend elbow FH.

[toly]

Originally Posted by sureshs

The particular way is the intuition of the pros. Just like it is meaningless to ask how Nadal produces a curved trajectory of the ball thinking that he uses mathematics for it.

As far as hitting 5 balls in a row, OK that may not be 5, it may be say 3.

Here is a simple calculation. TW University uses a racket tip speed at impact of 80 mph for ATP forehands. You can do a calculation of how much the tip will travel in a 4 ms dwell time, and it comes out to be 5.7 inches, or 2.2 ball diameters. Add in the fact that for a little more time the racquet will be maintaining its inertia after the ball leaves, and 3 balls in a row is not unimaginable.

Does it mean that the pro guides his racket in a straight line towards the target? No. It just means that he makes solid contact towards the intended direction as part of his up, forward and leftward trajectory of the swing.

I have said many times that topspin cannot be produced by purely rigid bodies. There has to be deformation in a certain dwell time. If you meet the ball in a certain way, it will be deformed and released in such a way that it will have both forward momentum and spin. If you don't meet it solidly, it won't have much pace but will have spin from a grazing motion. The solid meeting is what is commonly called hitting through the ball, and also produces the "pro sound" on impact. The reason it is emphasized is that club players often hit tentatively.

It looks like you cannot describe proper procedure about hitting through, because nobody can express that doesn’t exist. Instead you started using one of the vaguest terms as intuition.

To hit the ball solidly we have to increase normal component of the racquet speed relatively to tangential one, because the ball is absolutely symmetrical about its center. The bigger normal component the more solid contact will be.

Have you ever seen billiard pros game? They can create any spin with rigid bodies/balls. But, I’m not talking about pure rigid body, because it doesn’t exist.

[sureshs]

Didn't you say translation motion is not possible?

[sureshs]

Originally Posted by toly

It looks like you cannot describe proper procedure about hitting through, because nobody can express that doesn’t exist. Instead you started using one of the vaguest terms as intuition.

To hit the ball solidly we have to increase normal component of the racquet speed relatively to tangential one, because the ball is absolutely symmetrical about its center. The bigger normal component the more solid contact will be.

Have you ever seen billiard pros game? They can create any spin with rigid bodies/balls. But, I’m not talking about pure rigid body, because it doesn’t exist.

Billiard balls are better approximations to rigid bodies than tennis balls.

The intuition means to find the optimum swing path without calculations, which happens with tons of practice and talent. Call it muscle memory if you will.

I really don't folllow the other stuff that you are saying. During the dwell time, there is a forward and an upward force on the ball. And the more the normal force, the more forward force will be imparted.

In physics, mechanical forces are classified as either pull or push forces. In cases of deformation, there is a gray area. The strings that drag the ball with them for topspin may be considered pushing the ball upwards or pulling the ball upwards. But in no case is it pulling in. If the coordinate into the court is considered 0 at the point of contact of the ball and the strings, with the value increasing into the court, then the coordinate of the point on the strings becomes negative during the follow-thru, but the coordinate of the ball never becomes negative. So, at most there is a pulling (or pushing) motion upwards and outwards during the dwell time, but no pulling in motion.

[toly]

Originally Posted by sureshs

Didn't you say translation motion is not possible?

Sorry, but I don’t understand the question.

[sureshs]

Originally Posted by toly

However, most pros use bend elbow FH. So, they don’t care about hitting through.

Originally Posted by toly

About straight linear motion: She applies bend elbow FH technique, because she can use ISR, the fastest motion of the arm, to build translational motion of the ball.

You don't find any contradiction in the above?

In any case, it is not important.

[toly]

Originally Posted by sureshs

I really don't folllow the other stuff that you are saying. During the dwell time, there is a forward and an upward force on the ball. And the more the normal force, the more forward force will be imparted.

If racquet velocity has normal component only (normal to string bed) and point of contact is sweet spot, you hit pure flat FH (forget about strings actions). Because of the absolute symmetry of the ball there always should be solid contact.
If racquet speed has tangential component only, there never will be solid contact.

[bhupaes]

Originally Posted by toly

I think that Serena doesn’t use right arm bicep significantly, because she doesn’t bend additionally her elbow around and after impact. See picture below.

[picture deleted - see quoted post above]

About straight linear motion: She applies bend elbow FH technique, because she can use ISR, the fastest motion of the arm, to build translational motion of the ball. In case of straight arm ISR can create spin and practically zero translational speed. That’s why almost all WTA players use bend elbow FH.

I think you are right, but it becomes complex when you factor in the wrist layback angle, different grips, etc. Best to experiment and choose what works for you!