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/
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?
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..
