Article on Roddick Serve.... Supination

[vmiller]

OK John, Sounds good. Your honesty is commendable.

While we hope for some input from Brian, does anyone know the reasoning behind Vic's "scratch a friend's back" tip discussed earlier? Obviously he's promoting a drop further away from the body, but why? Maybe that answer will shed some light here.

[johnyandell]

Well not sure what that means. Even Andy isn't scratching someone else's back--it's along his right side. The tip flairs out, but I think there is a lot of smoke here over very little fire...

[BrianGordon]

some thoughts

O.K. - vmiller is getting into areas requiring an analytical approach far deeper than can be expressed here – however based on my research I’ll address his points, some of which show impressive depth of thought.

“I think the circular loop does not facilitate external rotation during the drop as well as the Andy/Pete drop does. If this is true, less external rotation is obviously going to result in less internal rotation, which means less racket speed.”

A loop by nature implies “circular” so I’m not sure how someone can have a non-circular loop. The fact that the shape of the loop varies among players is indicative of the vast array of segmental and joint rotations that influence this shape – the extent of the elbow bend being one of many of these rotations – however since the thesis of this thread seems to relate to elbow bend at or near the end of the wind up, we’ll go there.

Sentence 1 above is true – a very bent elbow will limit the extent (speed or displacement) of external rotation (see below) compared to a less bent elbow all else equal. This in turn could adversely effect internal rotation nearing impact. The suggestion that this would have a negative effect on racquet head speed assumes that all servers rely on internal rotation as major source of speed – which they don’t – MANY segment and joint rotations contribute to the speed of the racquet and many top servers don’t rely on internal rotation of the upper arm very much – instead opting for enhanced elbow extension, wrist flexion (sorry John), and trunk twisting rotation. The difference between D.N. and P.S. clearly reflects this difference in approach and nothing else.

“Here's what I think are a few convincing arguments that support the Andy/Pete drop.

1. More External Rotation - The hand and racket are further away from the humerus during the Andy/Pete drop. Gravity applied to the weight of the racket and hand during the drop is most of what externally rotates the humerus. Mathematically, this force being further from the humerus, which is the axis of rotation, will produce more torque. More torque on the humerus is more external rotation.”


This is true, however, the weight force is rather insignificant cause of the racquet drop via upper arm external rotation. Rather, the force applied to the upper arm through the shoulder, and occurring largely as a function of the upward trunk acceleration caused for the most part by the leg drive, is the primary cause of external rotation of the upper arm – that said the logic used by vmiller holds for this force as it does the weight force – that is, a less bent elbow will increase the lag of the arm as a function of the joint force.

“2. Better Transfer Across the Shoulder - The ~90 degree angle of the elbow in the Andy/Pete drop also results in the hand and racket being further away from the shoulder joint. Because of this, the transverse abduction (elbow pinned back) achieved during the backswing, or more importantly, the stretch across the front of the shoulder that it creates, is easier to maintain. The more intact this stretch remains, the more force that can be transfered from the torso to external rotation and it's rebound into internal rotation.

I'm not certain of the physiology behind this, but I think it's because the biceps must be somewhat contracted for the elbow to be closed. The biceps being contracted will reduce the range of motion of the shoulder making it more difficult to keep the shoulder stretched.”

As a purely speculative exercise this is at least entertaining. From a qualitative perspective establishing a stretch in the muscles that horizontally adduct the upper arm could provide contractile force benefits through lengthening the muscle, through pre-tensing the muscle, or some combination implying the “stretch shorten cycle”. The benefit in rotating the upper arm, however, would not be in “force transfer” but rather in the joint torque resulting from the enhanced muscle conditions. However, at the point of the motion where this would be important, it seems unlikely the deviation in the bend of the elbow would make much, if any difference. The far bigger factor would be the relationship between the upper arm orientation to the trunk AND!!! the angular acceleration and angular velocity of the upper trunk twist, something determined by trunk angle, angular momentum, etc. and that is one consequence of the lateral pinpoint stance used by D.N. – but this is a whole other story.

“And here are some other supporting ideas.

3. Quicker Arm Extension - A more closed elbow angle means that it will take longer to fully extend the arm before contact. Maybe this complicates timing? Since the arm has to be fully extended for internal rotation to translate into forearm pronation, maybe the added timing challenge could have an effect on pronation. Obviously pronation can occur independently of internal rotation, but it will be stronger if it's driven by internal rotation.”


Highly unlikely (and demonstrable) that time available for extension is an issue. However, range of motion is, and for one that CHOOSES to use elbow extension as a dominant contributor to racquet head speed, the more range of motion available – the better – and of course, more elbow bend increases this range of motion. Your leap from elbow extension, to internal rotation, to pronation is an interesting story but I don’t buy it, even assuming pronation was important to racquet speed which is generally is not.

“4. Racket Trajectory - The closed elbow angle results in the racket being closer to the body during the drop. This can cause the racket path from drop to contact to be more vertical than if the racket were further away from the body at the bottom of the drop. I would think that as the vertical component increases, ball velocity decreases. And we can all see from Pete that you don't really need to drastically increase the vertical component for spin.”

The racquet path on the serve for all top level servers is fundamentally vertical until very near contact. The distance of the racquet from the body at the end of the backswing would seem to be a very minor contributor to the forward transition which occurs due to the forces and torques applied to the racquet by the hand. Further the distance you mention is the result of many more segmental orientations than just the bend of the elbow.

“For what it's worth, I've been able to apply this drop concept to my serve with good results. It's even changed the way I think about producing spin.”

This is good – as is the level thinking you have applied to the serve – this is the makings of a researcher in Biomechanics – which unfortunately is what you’ll need to be to address the complex issues you put forth.

[vmiller]

Brian,

Thanks for taking the time to look at and respond to this thread. Your comments were very helpful for me to better understand what I was asking about.

This is good – as is the level thinking you have applied to the serve – this is the makings of a researcher in Biomechanics

Thanks. Most people just tell me I'm over analyzing, but I like getting to the bottom of how and why things happen and what can make them better.

[johnyandell]

Thanks to Brian from and we are excited about starting to publish his articles in the near future!

The only other thing I'll is that understanding why and how and making things better are not always the same things...

[vmiller]

we are excited about starting to publish his articles in the near future!

So am I.

The only other thing I'll is that understanding why and how and making things better are not always the same things...

I don't think they're ever the same thing. The former is typically a prerequisite for the latter.

[gzhpcu]

Brian,
Did I misread your response, or did you say that pronation is generally not a contributor to racket speed? If so, could you please explain, because I can't follow your reasoning. Also you seem to imply (if I understood correctly), that the wrist movement is also a contributing factor in the kinetic chain. Could you also please expand on this statement?
Thanks,

[vmiller]

Phil,

If you don't mind me trying to answer your question ...

Pronation by itself is a weaker movement than internal rotation and has less range of motion. I think the common perception that pronation provides racket speed is really based on it being combined with internal rotation.

[gzhpcu]

Thanks for the reply. Thinking about it, and trying it out, I have the impression that with pronation only, I get about 90 degrees of movement. Combined with internal rotation, I get 180 degrees.

[johnyandell]

What Brian is saying is that it's a very complex motion with many factors--and that different players may emphasize one component slightly more and produce similar--or different--results.

AND yes, what Brian's new research shows (he claims proves) is that there is forward wrist movement. No obviously it's true from the racket drop up to that netural position at contact. No one disagrees there. What I'll be interested in seeing is what his work shows about the overall picture. It's true that there is no "wave bye bye" with extreme forward wrist break at contact, but he and I had a long talk about it and let's just say there is probably room for us all to learn more precisely what happens. I don't see it in the video, but I'm very interested to hear about his work as it unfolds.

This is cutting edge stuff guys and we've already taken a big chunk (and too much) of Brian's valuabel time. We'll get a chance to ask him more after we start publishing his articles.

[shootermcmarc0]

will Brian be writing any articles on exposing the myth of the weight transfer, or are you doing that John?

[BrianGordon]

Pronation

Brian,
Did I misread your response, or did you say that pronation is generally not a contributor to racket speed? If so, could you please explain, because I can't follow your reasoning. Also you seem to imply (if I understood correctly), that the wrist movement is also a contributing factor in the kinetic chain. Could you also please expand on this statement?


Phil,

This an important question – so one more for the road – I did not mean to imply pronation was not a contributor – just that is generally not a relatively important contributor. The contribution a joint rotation makes to the speed of the racquet head depends on two factors: (1) the speed of the rotation AND (2) the geometric orientation of the axis of rotation to the position of the racquet face center at any time (v=omega X r ; for those who like equations). While the speed of rotation can be quite high for pronation, factor 2 often dictates that its impact on racquet head speed is small. This is easy to verify – simply position your arm and racquet as you would at contact and independently pronate your forearm – the effect of this action is unimpressive in moving the racquet head (more impressive with a bigger angle between the forearm and racquet – an angle with significant variation in high level servers) compared to other joint motion options. So assuming you can measure factor 1 & 2 it is possible to determine the contribution to racquet head speed from pronation and most other joint actions. I did and found on average for several high level servers that pronation contributes about 5% of racquet speed approaching contact – but hey, 5% is 5% - still relative to other joint contributions it is pretty insignificant (about #5). The pronation appears to be more important in positioning the racquet face, and to position the wrist joint in transition from ulnar deviation to wrist flexion – wrist motion as you call it which yes, is one of the bigger contributors to racquet speed near contact. How this contribution plays out in the kinetic chain is under investigation. These observations describe a portion of the kinematic chain. Hope this helps. Brian

[gzhpcu]

Thank you Brian. Will be looking forward to any additional information you share based on your research in this very interesting area.

[Bungalow Bill]

In my opinion, as different as Andy's and Pete's motions are, they have something in common during their drop that is not overly common. As you can see in the picture, there elbows remain close to a 90 degree angle, the racket basically comes straight down, and it's farther away from their body as a result.

Now look at Nalbandian. He severely closes his elbow causing the racquet to make a circular path behind his back and the racquet also stays closer to his body.

I've wondered if there's any meaning behind this for a long time. What I've come up with is that Andy and Pete's drop is more efficient in terms of transfer from torso rotation to internal shoulder rotation. As Bruce Elliot describes, the leg drive and torso rotation help to stretch the shoulder in the direction of external rotation during the drop, which is a big source of racquet speed. It seems that it would be a more efficient transfer if the racquet drops straight down like Andy and Pete rather than in a circular pattern like Nalbandian.

If you don't think I'm crazy yet, you're probably wondering what this has to do with Andy's supination. The Andy/Pete drop seems to be conducive to external rotation where the Nalbandian drop seems to work against it by bringing the elbow forward. External rotation and supination work together like internal rotation and pronation. So maybe there's more to Andy's unique racquet movement than just supination. Maybe it's the combination of the additional external rotation he gets from his style of drop and his supination during the drop that give him a larger range of motion for internal rotation.

I know it's a bit off this topic, but another problem I see with the Nalbandian like drop is that it can cause the elbow to come forward too early which I think weakens or breaks the link between the torso and shoulder that drives internal rotation. That's at least what I've found with my serve.

What do you think?

Gosh, I have trouble deciding on Pete's whether we are comparing apple to apples. With the clock at 123mph was the previous serve a first serve? I would assume so, since he is serving again and Pete's first serve could have definetly been a first serve. So what are these pictures.

The point to these pictures is to solely focus on the first one because Roddicks shoulder rotation and stretching is critical. This is the ENGINE that gives ROddick his power. I believe that the lower body and trunk motion before this position ALLOWS a person to stretch more in this area. Now the amount of stretch is dependant on the flexibility and the DNA of the person. But everything leads to this source of power. This will set the arm speed in motion, this is where the pedal meets the metal.

[Bungalow Bill]

In my opinion, as different as Andy's and Pete's motions are, they have something in common during their drop that is not overly common. As you can see in the picture, there elbows remain close to a 90 degree angle, the racket basically comes straight down, and it's farther away from their body as a result.

Now look at Nalbandian. He severely closes his elbow causing the racquet to make a circular path behind his back and the racquet also stays closer to his body.

I've wondered if there's any meaning behind this for a long time. What I've come up with is that Andy and Pete's drop is more efficient in terms of transfer from torso rotation to internal shoulder rotation. As Bruce Elliot describes, the leg drive and torso rotation help to stretch the shoulder in the direction of external rotation during the drop, which is a big source of racquet speed. It seems that it would be a more efficient transfer if the racquet drops straight down like Andy and Pete rather than in a circular pattern like Nalbandian.

If you don't think I'm crazy yet, you're probably wondering what this has to do with Andy's supination. The Andy/Pete drop seems to be conducive to external rotation where the Nalbandian drop seems to work against it by bringing the elbow forward. External rotation and supination work together like internal rotation and pronation. So maybe there's more to Andy's unique racquet movement than just supination. Maybe it's the combination of the additional external rotation he gets from his style of drop and his supination during the drop that give him a larger range of motion for internal rotation.

I know it's a bit off this topic, but another problem I see with the Nalbandian like drop is that it can cause the elbow to come forward too early which I think weakens or breaks the link between the torso and shoulder that drives internal rotation. That's at least what I've found with my serve.

What do you think?

Gosh, I have trouble deciding on Pete's whether we are comparing apple to apples. With the clock at 123mph was the previous serve a first serve? I would assume so, since he is serving again and this could be Pete's second serve?

The point to these pictures is to solely focus on the first one because Roddicks shoulder rotation and stretching is critical. This is the ENGINE that gives ROddick his power. I believe that the lower body and trunk motion before this position ALLOWS a person to stretch more in this area. Now the amount of stretch is dependant on the flexibility and the DNA of the person. But everything leads to this source of power. This will set the arm speed in motion, this is where the pedal meets the metal.