Biomechanics and injury prevention on the serve video
This seems to be an interesting video on biomechanics, pronation and injury prevention on the serve... Any Comments?
Science don't play tennis, as evidence by a hammer grip eastern and then continental.
However, he is explaing why we hit serves with a conti grip and pronation to make a flat serve work.
It has some interesting discussion, particularly dealing with how the arm can be rapidly straightened and not hyper-extend.
However, for the elbow extension issue, when I look at this video of what really goes on in the serve, the highest racket head speed follows very rapid rotation of the upper arm (internal shoulder rotation) while the elbow remains mostly straight. I think that his explanation should use a similar high speed video to clearly get across what he means with the elbow. I not clear watching the video. I believe the rapid straightening of the elbow in relation to internal shoulder rotation needs to be explained with a high speed video of the serve such as this one.
Notice the arm achieves a straight-up position and then there's rapid (0.03 sec) upper arm axial rotation seen best by looking at the elbow bones (ISR).
(Best method to do stop action on Vimeo is to click the play-pause button as fast as possible. Vimeo videos do not play on my Samsung Galaxy S2 android phone.)
Also, it's 2013, time that biomechanics researchers who know exactly what forearm pronation is and exactly what internal shoulder rotation is explain joint motions accurately and clearly in the proper terms and not use mind-muddling terms such as calling the overall arm motion 'pronation'.
Is there a single instructional serving video on the internet where the instructor uses the term "internal shoulder rotation" and also shows the upper arm rotation? The OP video clearly shows the upper rotation but does not use the term.
This is the closest that I have found so far but it is not a video. It uses the proper terms and refers to the research of Elliott and others.
I need to study this more as I am not familiar with the biomechanical terminology.
The original video mentions two ways of rotating:
1. Rotating from the elbow
2. Rotating from the shoulder
To me, it feels like I am leading with my bent elbow (flat serve) and then snapping up at contact, using mostly a rotation from the elbow.
I snap up and get to the "looking at the wrist watch" position and then feel my elbow straighten out.
At that point, I am not sure how much sensation I should feel in the biceps area.
I am very loose and relaxed and don't feel any pain but sometimes when straightening out the elbow and quickly snapping up I feel a little pull in the biceps area -- no pain but a pull -- don't know if that is normal...
Maybe at this point (after ball contact), I should switch from "rotating with the elbow" to "rotating with the shoulder" and see if that places less stress on the shoulder...
After reading about the serve and practicing it for decades I learned about internal shoulder rotation in 2011 in a TW thread and some earlier threads by Toly. It was a shock to me.
The biomechanical terms are good because these take each joint and name the motions that the joint is capable of. Therefore, internal shoulder rotation is an axial rotation of the upper arm. You can search it on the internet.
What the body is doing to get high racket head speed is taking the largest muscle attached to the arm, the lat, along with some others and rotating the smallest possible mass to get a very high racket head speed. The smallest mass is the straight arm axially rotated plus the light tennis racket held at changing angle as the arm rotates. This is shown very clearly in all the Vimeo pro serves.
You can also compare my puny internal shoulder rotation and see why I have the serve that I do <90 MPH and the pros have theirs >130 MPH.
Average players naturally do ISR to some extent. https://vimeo.com/55660219
I believe that serving with ISR is never forced and could cause injury if practiced incorrectly. Here are some known issues. With forceful and rapid ISR the small external shoulder rotator cuff muscles have to be conditioned to keep the ball of the humerus in place and to stop the arm rotation in the follow through. See recommended shoulder conditioning exercises. Easy, light exercises.
There are also the important safety issues related to technique such as the shoulder high orientation for the serve to minimize impingement risk. Just one very bad motion can cause injury.
1) Jim McLennan short video on the rotator cuff, impingement and serving
2) Todd Ellenbecker video on shoulder anatomy, impingement, and serving. At about minute 8 he describes the same issue as McLennan but in more detail.
If you are concerned because you are having pain, how can you determine that the technique that you use is OK? You have to study and know the proper technique and verify that you are doing it with high speed video or find a well qualified instructor. Keep in mind that the more rapid motions during the serve cannot be seen by eye or even 60 fps video so an instructor who uses HSV is a plus.
Thanks all for the posted vids. Funny, I was just thinking yesterday to search some old threads for this info. Recall seeing something a little while back about this subject. That video (if memory serves...pun intended) was a comparison of modern vs classic serves (classic being before both feet could leave the ground). The vid also talked about injury prevention.
The rule was changed in 1961 according to this reference.
"There was one more rule change that affected serving, although it took awhile for the implications to be understood. In 1961, the International Lawn Tennis Federation abandoned the requirement that servers keep one foot on the ground."
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