ISR: Upper Limb Power Contributors To The Serve

Raul_SJ

G.O.A.T.
Contributions of Upper Limb Segment Rotations During the Power Serve in Tennis

The major contributors:

Internal rotation of the upper arm (54.2%),
Flexion of the hand (31.0%),
Horizontal flexion and abduction of the upper arm (12.9%),
Racket shoulder linear velocity (9.7%).


http://www.exeter.ac.uk/media/unive...alexeter/documents/iss/Elliot_et_al__1995.pdf
ISR brings the racket from edge-on at the big L to face-on at impact. ISR is driven by large muscles and has the force to accelerate the racket. Pronation is driven by small forearm muscles and probably plays a negligible role in acceleration. I can't see pronation leading to impact in high speed videos, however, it is difficult to see in videos without markers. But I can easily see ISR as the upper arm rotates.

Yes, I tried this out. To isolate mainly the upper limb contributors, I served starting from the "L" position with and observed the following:

1. I could get a relatively powerful serve using essentially only hand flexion (No ISR). This was in agreement with the 31% hand flexion contribution reported by the study.

2. I confirmed that ISR was as you described above. When I internally rotated the shoulder, the pronation inevitably occurs. Correct?

My question:

The study reports ISR as contributing 51% of upper limb segment power.

But what is the contribution to power from pronation alone? Was that measured and reported in the study?

Or said another way: Is it possible to hit a serve using only pronation + hand flexion and little to no ISR?
 

Chas Tennis

G.O.A.T.
Contributions of Upper Limb Segment Rotations During the Power Serve in Tennis

The major contributors:

Internal rotation of the upper arm (54.2%),
Flexion of the hand (31.0%),
Horizontal flexion and abduction of the upper arm (12.9%),
Racket shoulder linear velocity (9.7%).


http://www.exeter.ac.uk/media/unive...alexeter/documents/iss/Elliot_et_al__1995.pdf


Yes, I tried this out. To isolate mainly the upper limb contributors, I served starting from the "L" position with and observed the following:

1. I could get a relatively powerful serve using essentially only hand flexion (No ISR). This was in agreement with the 31% hand flexion contribution reported by the study.

2. I confirmed that ISR was as you described above. When I internally rotated the shoulder, the pronation inevitably occurs. Correct?

My question:

The study reports ISR as contributing 51% of upper limb segment power.

But what is the contribution to power from pronation alone? Was that measured and reported in the study?

Or said another way: Is it possible to hit a serve using only pronation + hand flexion and little to no ISR?

I'm glad that you are getting into this in a serious way. I have to warn you that once you get through the membrane of understanding you can never go back, takes about 4 hours with a relaxed & open mind and some accurate research........

DON'T DO THESE MOTIONS VERY FORCEFULLY


" 2.....................................When I internally rotated the shoulder, the pronation inevitably occurs. Correct?"
No. Not as the terms are defined for joint motions. Try bending the elbow and pronating. Now do ISR with a bent arm. With ISR the wrist and forearm go all over the place. Now straighten the arm. Try only pronation and see how the wrist moves. (You may have to hold your elbow still to make sure that ISR is not occurring.) Try only ISR and see how the wrist moves. Try them together.

"Is it possible to hit a serve using only pronation + hand flexion and little to no ISR?"
Hold the racket at an angle to the forearm with the elbow bent. Use just pronation. Feel the strength of the forearm muscles that produce racket head speed.
Now hold the straight arm straight out from the shoulder to the side. Hold the racket at an angle to the forearm. Use ISR to produce racket head speed. Feel the strength of the lat and pec muscles that can drive ISR. The lat and pec are pre-stretched 30 millisecond before impact and can therefore shorten very rapidly, twitch-like. See the OP serve video.

See the similar table in this much later 2006 publication, Table 2.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/

tbl2



Power. Forget the often used term 'power'. Power is measured in watts and nobody really can measure power or define what it means for a tennis stroke. It is a very mushy term for discussing tennis. Also, power varies in time during the service motion. At times some muscles supply power and then later they don't. For example, the leg muscles may supply 'power' early in the service motion but at impact they are supplying almost no power because the feet are off the ground and the legs have straightened.

Velocity. What Elliott et al did was to take multiple high speed film cameras, place markers on body parts and rackets and measure racket head velocity contributions from each joint motion leading to impact. The tables above represent the racket head velocity contributions at impact. To get the contribution of a joint to racket head speed you measure the joint angular velocity, measure the distance from the joint to the center of the racket head and multiply the joint's angular velocity times the distance. This is discussed in the report. Because the serve is a 3D motion, and 3D cannot be measured with a single camera, 3 cameras were used. The table represents the velocities contributed in the forward direction by each of the named motions associated with a joint.

I believe that the tables represent only velocities in the direction toward the other court because of the following information from the report. If the racket is going up and forward, only the forward component is represented in the table.

"At impact, a mean velocity of 3 1.0 m . s-' (in a line perpendicular to the baseline
toward the opponent: x axis)
for the center of the racket head was higher than
the 27.0 m . s-' reported for the player filmed by Sprigings et al. (1994) and
similar to the mean values re@rted by Elliott et al. (1986) and van Gheluwe
and Hebbelinck (1985) for high-performance college and international level
players, respectively. The average peak velocity of the center of the racket head
(32.9 m . s-') was recorded a mean 0.005 s prior to impact."

There is also a later 1999 or 2000 report on the serve with more detail.

Joint Motions Don't Necessarily Mean Muscles Have Pulled at the Joint. Also, just because the angular velocity of a joint is very high or accelerating it does not mean that the joint or its associated muscles are supplying much force. Take a racket in your hand and swing it across in front of your chest with completely relaxed forearm muscles, suddenly stop your arm, your wrist flexes rapidly when you stop. Just because a joint rotates or accelerates does not indicate that muscles are at work. Especially, wrist joint motions can occur because the arm is being moved around by other muscles of the body. Probably the wrist flex in the table is really a secondary joint motion probably resulting from ISR and earlier elbow extension.



Is anyone following this stuff?
 
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taurussable

Professional
Flexion of the hand (31.0%),
Horizontal flexion and abduction of the upper arm (12.9%),
Racket shoulder linear velocity (9.7%).

what are these?
 

GuyClinch

Legend
We don't talk about hand flexion here. Because that's commonly known as wrist snap. :p And if we do talk about it we call it 'passive.' Any joints contribution that the TW intelligentsia doesn't like is 'passive'.. It gets you out of any sticky research contradictions..
 

GuyClinch

Legend
Is anyone following this stuff?

Not really because ISR is part and parcel of every single serve. You cannot throw effectively without using ISR. Saying ISR is the key to serving is like saying the quadriceps are important in running..

Leg Flexion is important in running! OMG I have to start using leg flexion.

Sure you can get more power out of your serve with correct technique and thus more ISR. But what does it matter if intellectually we know ISR is important? Not much..

We know low elbow will impede ISR. We know that not opening the chest will impede ISR and so on and so forth. But we could just say this will mess up your serve - because again part and parcel of the serve is ISR.

You can't throw without internal shoulder rotation...
 

LeeD

Bionic Poster
Strong throwing motion, coupled with a learned racket whip effect, gives the fast serves.
Add some legs, add some long levers, add some height, and you get a world class serve.
 

Chas Tennis

G.O.A.T.
Not really because ISR is part and parcel of every single serve. You cannot throw effectively without using ISR. Saying ISR is the key to serving is like saying the quadriceps are important in running..

Leg Flexion is important in running! OMG I have to start using leg flexion.

Sure you can get more power out of your serve with correct technique and thus more ISR. But what does it matter if intellectually we know ISR is important? Not much..

We know low elbow will impede ISR. We know that not opening the chest will impede ISR and so on and so forth. But we could just say this will mess up your serve - because again part and parcel of the serve is ISR.

You can't throw without internal shoulder rotation...

When do you think that this obvious throwing joint motion became known to baseball biomechanical researchers? The decade is close enough.

When do you think that was this obvious fact was understood by tennis biomechanical researchers? The decade is close enough.
 
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I think that the studies cannot devide between pronation and ISR. both is contributing, but ISR is probably the bigger component because the ISR muscles are bigger (pec and lat are the main ISR muscles and they are much larger than the pronator of the forearm).

also don't forget that ISR does not only square the racket but also moves the hand forward because ISR starts well before the arm is extended.

ISR is also one of the biggest driving forces in baseball pitching and in pitching turning of the hand does not contribute to power so ISR has to be used before the arm is extended.

you don't extend the arm and then ISR to drive the racket, the ISR (together with elbow extension) is what causes the forearm whip. it of course also helps to turn the racket together with pronation.

serving is basically the same as throwing a ball.
 
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When do you think that this obvious throwing joint motion became known to baseball biomechanical researchers? The decade is close enough.

When do you think that was this obvious fact was understood by tennis biomechanical researchers? The decade is close enough.

ISR in throwing has been known very long (although it should have been known earlier), I think it was first mentioned like 20 years ago.

in tennis biomechanics is just a quite new field, tennis used to be a very traditional sport focussing more on "positions" rather than biomechanic principles.

only in the last 20 years the biomechanical principles (ground reaction force, rotation of the body, kinetic chain) are really used in tennis but all those principles have been used and described in track and field as early as the 1950s by russian scientists.
 

Chas Tennis

G.O.A.T.
ISR in throwing has been known very long (although it should have been known earlier), I think it was first mentioned like 20 years ago.

in tennis biomechanics is just a quite new field, tennis used to be a very traditional sport focussing more on "positions" rather than biomechanic principles.

only in the last 20 years the biomechanical principles (ground reaction force, rotation of the body, kinetic chain) are really used in tennis but all those principles have been used and described in track and field as early as the 1950s by russian scientists.

I disagree completely that 20 years is a long time ago!
 

Chas Tennis

G.O.A.T.
I think that the studies cannot devide between pronation and ISR. both is contributing, but ISR is probably the bigger component because the ISR muscles are bigger (pec and lat are the main ISR muscles and they are much larger than the pronator of the forearm).

It's hard to distinguish accurately especially because any pronation prior to impact is hard to see and the skin does not move exactly with the muscles and bones inside.

also don't forget that ISR does not only square the racket but also moves the hand forward because ISR starts well before the arm is extended.
I don't agree that ISR starts "well before" the arm is straight. Do you have any video or references?

ISR is also one of the biggest driving forces in baseball pitching and in pitching turning of the hand does not contribute to power so ISR has to be used before the arm is extended.

Agree.

you don't extend the arm and then ISR to drive the racket, the ISR (together with elbow extension) is what causes the forearm whip. it of course also helps to turn the racket together with pronation.

I think that the elbow extends first and the arm becomes straight and then ISR starts. But things are very fast then. Will look at still sequences in some other threads. Some servers probably do overlap the elbow extension and ISR. ?

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You are right for this video. The arm is still a little bent in the first frame and 4 milliseconds later ISR has occurred or has been occurring. I don't have the frame earlier uploaded for posting. If you are interested I could get it and we could see what it shows.

The last two frames are the frame before impact and impact. Two middle frames are missing because of the TW limitation on only 4 pictures per reply.

Here is the video-
https://vimeo.com/27528701
Very close timing of the end of extension and start of ISR.

You can do stop action single frame on Vimeo by holding the SHIFT KEY and using the LEFT or RIGHT ARROW KEYS. If it does not work let me know as there is a work around.

serving is basically the same as throwing a ball.
 
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I'm not saying ISR is over before the arm is extended but is definitely does start before the arm is extended. extension and ISR is IMO one fluid motion.
 

taurussable

Professional
ry bending the elbow and pronating. Now do ISR with a bent arm. With ISR the wrist and forearm go all over the place. Now straighten the arm. Try only pronation and see how the wrist moves. (You may have to hold your elbow still to make sure that ISR is not occurring.) Try only ISR and see how the wrist moves. Try them together.

"Is it possible to hit a serve using only pronation + hand flexion and little to no ISR?"
Hold the racket at an angle to the forearm with the elbow bent. Use just pronation. Feel the strength of the forearm muscles that produce racket head speed.
Now hold the straight arm straight out from the shoulder to the side. Hold the racket at an angle to the forearm. Use ISR to produce racket head speed. Feel the strength of the lat and pec muscles that can drive ISR. The lat and pec are pre-stretched 30 millisecond before impact and can therefore shorten very rapidly, twitch-like. See the OP serve video.

I especially like the try this try that instructions. Lots of feel and understanding come from the experimentation.
 

taurussable

Professional

Chas Tennis

G.O.A.T.
............

101 degrees means the upper arm is already not in line with shoulder(11 degrees past in line position), will this cause impingement?

My opinions - See the Ellenbecker video.

Where 90° shoulder abduction is straight out, arm perpendicular to the standing body. (0° is arm down against side.) -

I have read that in some people shoulder impingement can begin with as little as 65° of abduction - that is, when arm is still 25° down from 90°. I don't know under which circumstances, which motions, or how rare those affected people are. But there might be significant variation among individuals.

When shoulders are examined with MRIs or X rays, the reports sometimes state that there is a 'predisposition' to impingement from the individual's shoulder structure. That's what the report said for my imaging when I had a rotator cuff injury, mild suspraspinatus tears, in my non-tennis shoulder (probably from gym work). The tennis shoulder has been fine.

Most high level servers have their arms higher than a rough line between the shoulder extended. The data in the ASMI thread agree. My videos from behind show a sample of high level severs and a few amateurs. The differences in the shoulder orientations between the amateurs and pros stand out.
https://vimeo.com/user6237669/videos

In 2013, Federer had some back problems. That may have contributed to his shoulder orientation shown here. Measures at 34° up from line between the shoulders extended.
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The "in line" description between the two shoulders is a rough guide. Another variable is that the scapula moves around on the back and tilts. The scapula's position will likely affect impingement.
Google search: scapula movement image
https://www.google.com/search?q=sca...0G5PfsAT7s4DgDA&ved=0CCkQsAQ&biw=1113&bih=688

If the shoulder tissues become swollen that probably increases impingement or the risk of impingement.

If your shoulders have posture problems those might increase the risk. Mine are a little 'rounded' now which means the scapulae are a little on the side instead of back more. I've been stretching recently and think that they may have moved a little.

I believe that the Ellenbecker advice applies to the internal shoulder rotation serve performed in the usual way. For other serving techniques....??

As always, camera viewing angle affects what you see in a frame or picture.

There are a lot of factors and uncertainties. But if you raise your arm too high on the serve while your shoulders are too level you most likely increase your risk of impingement according to the Ellenbecker video. See the video. I believe it also includes some conditioning exercises.
 
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