Update for those interested

[BrianGordon]

Happy holidays and Merry Christmas to the tennisplayer community – been a bit tied up lately but for those interested in my work I provide the following update:

In my article that broke down the speed of the racquet into contributions from the various joint rotations on the serve, I acknowledged that current methodology precluded precise differentiation of the contributions from shoulder internal rotation and forearm pronation when the elbow neared full extension (second half of the upward swing).

In my recently defended dissertation, I developed a method to make this differentiation and reevaluated the final instants prior to contact – my method allowed accurate measurement up to 0.007 s prior to contact for the twist rotations of the hitting arm segments (upper arm and forearm) – interesting values at this time:

Shoulder twist rotation: 43% of racquet speed.
Forearm twist rotation: -5% of racquet speed.

The implication is that the rotation observed in the forearm (pronation) is purely a result of the internal rotation of the upper arm at the shoulder joint - independent rotation of the forearm is actually in the direction of supination RELATIVE to the upper arm – an important coaching cue in my opinion.

Other findings were that flexion at the wrist accounted for 36% of racquet speed at 0.007 s prior to impact and 43% of racquet speed at impact – higher than previously measured – the kinetic source of the flexion was not investigated in this work.

Just prior to impact, shoulder internal rotation and wrist flexion combined accounted for 79% of racquet speed. Upper trunk twisting rotation and elbow extension combined kicked in an extra 17% (in about equal proportion). Combined, these four sources accounted for 96% of the racquet speed.

These values are averages of a group of nine D1 players, predominantly made up of members of the last two national championship teams (sorry – no pros).

On to the forehand … Happy New Year!!!

[uspta990770809]

couple of thoughts

Happy holidays and Merry Christmas to the tennisplayer community – been a bit tied up lately but for those interested in my work I provide the following update:

In my article that broke down the speed of the racquet into contributions from the various joint rotations on the serve, I acknowledged that current methodology precluded precise differentiation of the contributions from shoulder internal rotation and forearm pronation when the elbow neared full extension (second half of the upward swing).

In my recently defended dissertation, I developed a method to make this differentiation and reevaluated the final instants prior to contact – my method allowed accurate measurement up to 0.007 s prior to contact for the twist rotations of the hitting arm segments (upper arm and forearm) – interesting values at this time:

Shoulder internal rotation: 43% of racquet speed.
Forearm pronation: -5% of racquet speed.

The implication is that the rotation observed in the forearm (pronation) is purely a result of the internal rotation of the upper arm at the shoulder joint - independent rotation of the forearm is actually in the direction of supination RELATIVE to the upper arm – an important coaching cue in my opinion.

Other findings were that flexion at the wrist accounted for 36% of racquet speed at 0.007 s prior to impact and 43% of racquet speed at impact – higher than previously measured – the kinetic source of the flexion was not investigated in this work.

Just prior to impact, shoulder internal rotation and wrist flexion combined accounted for 79% of racquet speed. Upper trunk twisting rotation and elbow extension combined kicked in an extra 17% (in about equal proportion). Combined, these four sources accounted for 96% of the racquet speed.

These values are averages of a group of nine D1 players, predominantly made up of members of the last two national championship teams (sorry – no pros).

On to the forehand … Happy New Year!!!

Just a couple of quick thoughts:

1. If the other movements of the body prior to the last wrist flexion and shoulder rotation have not put the racket and body in the right position with the racket moving in the correct planes with the right momentum, the player would not be able to get that maximum force from that wrist flexion and shoulder rotation

2 I'm always saying there is way too much emphasis on trying to get players to use more flexion in their legs and jump into the serve at the expense of a more consistent and even more efficient and therefore powerful service. This analysis doesn't leave room for much contribution to the final racket head speed from leg drive.

3. Is any part of the analysis considering speed of the ball relative to speed of the racket head? Racket head speed is essential, but if it isn't coincident with the force direction of the racket head, it isn't going to make the ball go that fast. They do this kind of thing a lot in golf and, in golf, the angle of approach of the clubhead is really important relative to ball spin and ball carry and stop. Obviously tennis is a different story, but I wonder about the serves that had the best percentage transfer of racket head speed to ball speed.

Looking forward to seeing the work on the forehand soon, Brian.

don brosseau

[BrianGordon]

Don - good points as usual:

1. If the other movements of the body prior to the last wrist flexion and shoulder rotation have not put the racket and body in the right position with the racket moving in the correct planes with the right momentum, the player would not be able to get that maximum force from that wrist flexion and shoulder rotation

How true - believe this was acknowledged in the original article.

2 I'm always saying there is way too much emphasis on trying to get players to use more flexion in their legs and jump into the serve at the expense of a more consistent and even more efficient and therefore powerful service. This analysis doesn't leave room for much contribution to the final racket head speed from leg drive.

The values given are instantaneous, specifically referencing a moment just prior to impact, and a time at which difficulties were encountered in the determination of some contributions in earlier research - contribution patterns critical to player development in my opinion.

At that time the legs have completed their push for high level players (and the feet are off the ground) - as such, it is not surprising that leg joint or segment rotations are not linked to racquet speed.

That said, clearly the earlier actions of the legs are critical for producing the conditions that allow the cited joint rotations to do what they do at the time referenced - directly or indirectly. I refer anyone interested in my story of the role of the legs to at least the 2 back swing articles on this site.

3. Is any part of the analysis considering speed of the ball relative to speed of the racket head? Racket head speed is essential, but if it isn't coincident with the force direction of the racket head, it isn't going to make the ball go that fast. They do this kind of thing a lot in golf and, in golf, the angle of approach of the clubhead is really important relative to ball spin and ball carry and stop. Obviously tennis is a different story, but I wonder about the serves that had the best percentage transfer of racket head speed to ball speed.

My interest is how the body works to produce endpoint (racquet face center) velocity (speed and direction) - the bio in biomechanics - the contact velocity vector is controlled according to the goals of the study by requiring certain characteristics of the shot (ball speed/spin, placement, etc.) before a stroke is selected for analysis.

Though obviously important, the ball/racquet impact dynamics are not that interesting to me (at this point anyway) so I'll leave that to the physicists.

[jasonfrausto]

Interesting research Brian, will all of this information be appearing in the form of an article in 2010?

[BrianGordon]

Interesting research Brian, will all of this information be appearing in the form of an article in 2010?

Thanks Jason-

That project was all about methodology - the only information potentially of interest here is what I provided - not enough for an article really so I just threw it out there.

Anyway, I'm ready to do more work on the other strokes - have great data I need to analyze so I can write up some stuff here - recent events have put me a bit behind in that regard.

Plus John has come up with some great ideas for some really powerful info for the site that I expect could take a fair amount of my time when we get rolling - after all that I'll be back to the serve - best - Brian

[bottle]

Fascinating as always, providing solid new measures to try. What, for instance, if the player thought the "snap" everyone commonly refers to was made up of wrist straightening or curling combined with independent twist from the forearm? You're telling me, I believe, no matter how scholarly and detached you choose to be in your language, "Try to get more out of shoulder twist just before contact, Bottle-- get the emphasis right!" And thanks.

It's my theory that the innocence of the tennis mystics is long gone, leaving the inquisitive with nowhere to go but reason and science, if they actually want to improve, although they can then revert to something more grounded in neuro-science, where there is plenty of mystery all over again.

[bottle]

"How can I know what I think until I read what I write."
-- James Reston late of the New York Times

Okay, so I respond, and then I'm more personally involved, so the next time I re-read the thing, maybe I see more.

To read anything of substance, one had better go over it a number of times-- no?

"independent rotation of the forearm is actually in the direction of supination RELATIVE to the upper arm-- an important coaching cue in my opinion."

WOW! You're talking about letting the forearm spring backward for a longer, more cushioned contact!

[BrianGordon]

Bottle-

Scholarly is an artifact of the largely useless paper on the wall of my garage – detached is my nature and the legacy of my recently departed father (the true scholar in my family) – the language I use is a compromise to exist in dual worlds and an attempt to say the most with the least – admittedly it rarely works out – but it is what it is.

What I (and others) have known for some time is that the twist rotations of the hitting arm segments are critical to racquet head speed near contact. Some total (shoulder internal rotation + independent forearm pronation) is used by all players. What is becoming increasing clear to me is that the extent to which the total is dominated by shoulder internal rotation speaks volumes about the prowess of the server.

The forearm can be rotated by twisting the upper arm using the shoulder internal rotating muscles (because the segments are connected); or it can be rotated independently by rotating the radius about the ulna using the forearm musculature (true pronation); or both. Problem was, until very recently I could not tell the difference when the arm was nearly straight. Now that I can, evidence suggests that better servers use the former – but it is more difficult to master and probably comes with increased danger of injury.

But even if the forearm is being rotated primarily by twisting the upper arm at the shoulder joint, the independent rotation capability of the forearm dictates that some effort is required to maintain the desired orientation of the forearm relative to the upper arm, especially with a racquet tending to make it lag behind.

So ... with the extreme shoulder internal rotation speed seen in better servers, the fact that the forearm is supinating RELATIVE to the upper arm (even though it is internally rotating relative to the ground) could be due to the fact it simply can’t keep up, or it is being manipulated to ensure the entire hitting arm/racquet structure is not over rotated at contact. I don’t know which, but don’t think the purpose is to cushion the contact – I could be wrong.

[uspta146749877]

Cues-how to utilize them?

Brian,
could you elaborate how coaches could use
a cue mentioned by you below
--->your quote
The implication is that the rotation observed in the forearm (pronation) is purely a result of the internal rotation of the upper arm at the shoulder joint - independent rotation of the forearm is actually in the direction of supination RELATIVE to the upper arm – an important coaching cue in my opinion.

[bottle]

Brian,

I admire your detachment and furthermore think that the best communication ever happens when an author doesn't tell too much but induces the reader to figure something out or maybe just lets the chips fall where they may.

So, my flight of fancy about "cushioning" came from my perhaps overly hasty wish mentally to connect with that species of "mondo" in a forehand where strings seem to go backward even as they actually go forward (ulp!).

But I can certainly understand that no server ever might wish to do anything that would reduce total racket head speed. The trouble is a snowstorm that's keeping me from trying out the new ideas and experimenting and having a lot of fun.

So what's the "takeaway" from these Christmas gift posts, as a hack newspaperman (but not a journalist) might say? Well, it's going to differ from reader to reader, but for me it's:

1) Shoulder twist more than forearm twist

2) Work on different shoulder twist, forearm twist, wrist flexion combinations and be free-thinking about it!

3) Let height of bounce relative to crossbar on opposite fence be the sole arbiter, since topspin serves are my sole concern just now.

4) Remain open about arm extension sequence-- triceps first, passive second comes to mind through the suggestion that late twist from the shoulder is now going to become more prominent.

5) If wrist flexion contributes 36 per cent of racket speed seven thousandths of a second before contact and 43 per cent at contact, would it hurt to try for 50 per cent as you came off of the ball whether you achieved that or not?
The point is that this will be new thinking for many people-- especially the ones who thought wrist flexed and then pronation hit the ball-- both now will hit the ball.

6) Don't clot up this business end of the serve too much. Keep things simple even with the new knowledge. (I express my humble hope for myself.)

7) Turn on the shoulder twist about halfway through arm extension.

Thanks so much for the new ideas based on empirical research. New ideas, as I tried to say, are "gifts" in my view, and there may not be enough of them.

[BrianGordon]

Brian,
could you elaborate how coaches could use
a cue mentioned by you below
--->your quote
The implication is that the rotation observed in the forearm (pronation) is purely a result of the internal rotation of the upper arm at the shoulder joint - independent rotation of the forearm is actually in the direction of supination RELATIVE to the upper arm – an important coaching cue in my opinion.

The very general way to improve the input from any joint contribution is to use technique to (see serve mechanics series for definitions):

1. increase available range of motion
2. to improve the contractile conditions of the surrounding muscle through counter motion (reversal and timing), muscle length/lever arm optimization, and creating conditions where muscles can accomplish the same task in slower contractile conditions
3. to create beneficial joint forces through sequencing the motion of surrounding segments

and to use periodized resistance type training to:

1. stabilize (protect) the joint
2. increase the force that can be produced at high contraction speeds in the muscles moving the joint
3. improve the endurance capabilities in #2.

The coaching cue that statement has to do with is simply : Which joint should really be the focus? - because specific adaptations of the general points above to independent forearm pronation are considerably different from the adaptations for shoulder internal rotation.

The decision and adaptations are the art of coaching - I merely report - each coach must decide on case by case basis.

[BrianGordon]

Brian,

I admire your detachment and furthermore think that the best communication ever happens when an author doesn't tell too much but induces the reader to figure something out or maybe just lets the chips fall where they may.

So, my flight of fancy about "cushioning" came from my perhaps overly hasty wish mentally to connect with that species of "mondo" in a forehand where strings seem to go backward even as they actually go forward (ulp!).

But I can certainly understand that no server ever might wish to do anything that would reduce total racket head speed. The trouble is a snowstorm that's keeping me from trying out the new ideas and experimenting and having a lot of fun.

So what's the "takeaway" from these Christmas gift posts, as a hack newspaperman (but not a journalist) might say? Well, it's going to differ from reader to reader, but for me it's:

1) Shoulder twist more than forearm twist

2) Work on different shoulder twist, forearm twist, wrist flexion combinations and be free-thinking about it!

3) Let height of bounce relative to crossbar on opposite fence be the sole arbiter, since topspin serves are my sole concern just now.

4) Remain open about arm extension sequence-- triceps first, passive second comes to mind through the suggestion that late twist from the shoulder is now going to become more prominent.

5) If wrist flexion contributes 36 per cent of racket speed seven thousandths of a second before contact and 43 per cent at contact, would it hurt to try for 50 per cent as you came off of the ball whether you achieved that or not?
The point is that this will be new thinking for many people-- especially the ones who thought wrist flexed and then pronation hit the ball-- both now will hit the ball.

6) Don't clot up this business end of the serve too much. Keep things simple even with the new knowledge. (I express my humble hope for myself.)

7) Turn on the shoulder twist about halfway through arm extension.

Thanks so much for the new ideas based on empirical research. New ideas, as I tried to say, are "gifts" in my view, and there may not be enough of them.

Bottle-

That is quite an impressive bullet list I must say - I sincerely hope the ideas provided prove beneficial to your serve - sorry about the weather - still, I wish you a great holiday season and a lot of experimental joy - Brian

[uspta990770809]

Direction for a useful article

The very general way to improve the input from any joint contribution is to use technique to (see serve mechanics series for definitions):

1. increase available range of motion
2. to improve the contractile conditions of the surrounding muscle through counter motion (reversal and timing), muscle length/lever arm optimization, and creating conditions where muscles can accomplish the same task in slower contractile conditions
3. to create beneficial joint forces through sequencing the motion of surrounding segments

and to use periodized resistance type training to:

1. stabilize (protect) the joint
2. increase the force that can be produced at high contraction speeds in the muscles moving the joint
3. improve the endurance capabilities in #2.

The coaching cue that statement has to do with is simply : Which joint should really be the focus? - because specific adaptations of the general points above to independent forearm pronation are considerably different from the adaptations for shoulder internal rotation.

The decision and adaptations are the art of coaching - I merely report - each coach must decide on case by case basis.

Brian,
I realize your goal is simply to "report" and let the chips fall where they may to be used as anyone would choose. But it seems the information here is a natural lead in for you to do a collaborative article with a kinesiologist/trainer who can take your data and apply it to a simple training program to develop the "necessary" musculature to hit just an effective serve. We see so many kids that "look" like they are doing everything right, but they just don't have any real snap. I keep waiting for them to "get a little stronger". I know I will try to apply what you are saying to help some of my students accelerate their trip through that wasteland of ineffectual "pop" in their motion. It hadn't occurred to me that they weren't just not strong enough, but that they weren't strong enough in specific muscles that they could significantly strengthen with appropriately focused training.

For research purposes, it might be interesting to get together with coach/trainer who could test some young kids and see what such a focused strength program could achieve. Relatively short term testing(6 to 9 mos) with 9 to 12 year olds (can't do too much strength training with them anyway) could lead to some very interesting results.

In any case, I'd love to see your list of which muscles to strengthen in some priority, perhaps even some weighting for emphasis. Okay, I'm wishing, but it's Xmas!

all the best to you Brian,
don

[rosheem]

Back on page 25 or so of Bottle's "New Year's Serve" thread, I wrote:

The hand can rotate more slowly than the entire arm, which enables prolonged contact and delayed acceleration.

I was describing this based only on how it feels to me, but it's nice to see that maybe I was right on.

Whether or not there is really "prolonged contact and delayed acceleration" doesn't matter. The key point is that there is a level of micro-control within the overall stroke, and it is made possible by the ability of the forearm to rotate independently of the bigger shoulder rotation.

Brian wrote:

or it is being manipulated to ensure the entire hitting arm/racquet structure is not over rotated at contact.

I think this is an accurate description. On another forum, I wrote that control on the serve is more about how you come OFF the ball than anything else. The way the independent rotations work together allows the shoulder to do the powering while the hand does the shaping.

Just my personal observations...I'm not a coach or anything.

[tennisplayer]

Brian, thanks for posting these findings. I have a question on the role of the triceps, especially in kick serves. As the upper arm is rotating, the elbow is also straightening out to provide the upward (and sideways) component of the racquet head movement. Is this straightening out happening passively (as a result of the other movements), or is the triceps being actively engaged to do so?

Sorry if this is taking you out on a tangent, but this question has been bothering me for a while...