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Old 03-01-2013, 10:55 PM   #72
toly
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Quote:
Originally Posted by SystemicAnomaly View Post
Disagree with this. When this wrist is c0cked, it is not "intense wrist extension" (whatever that means). The c0cking of the wrist is partly wrist extension and partly radial deviation. On the upward swing to contact, the wrist moves from the c0cked position to a fairly neutral position at contact. I would not characterize this wrist action as a "wrist snap".

The problem with that phrase is that it is very misleading. Many/most players mistakenly assume that the wrist will be in flexion (position) either before or after contact when told to "snap the wrist". The wrist should not be in a position of flexion before contact or after contact. It is not even necessary to assume a position of flexion after contact either. However, some elite players may have a slight flexion well after contact.

The racket does move up on edge. However, for a flat serve,most of this "on edge" motion is prior to the big L (prior to image #1 in your sequence). For a spin serve, the racket moves "on edge" longer.
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Here is Chas Tennis post about “Definition & usage of Pronation & Supination.
Quote:
Originally Posted by Chas Tennis View Post
Maybe these arguments on supination & pronation are made worse by the seriously different definitions of terms. I know I have had a very hard time....believing ISR was pronation for decades until 2011, etc.

1) Position. The anatomical definitions of pronation and supination are defined for position of the forearm and not movement of the forearm. They reference 0 as a defined position of the "anatomical position". It is very clearly defined. You can search and find these definitions on the internet. In this video the forearm pronation and supination are measured.

http://www.youtube.com/watch?v=PLE1uAWCrVU

2) Common Usage for Rotational Motion in a Direction. For motion, for a right handed person looking out along the axis of the forearm, pronation is elbow-to-wrist rotation in the counter-clockwise direction and supination is forearm elbow-to-wrist rotation in clockwise direction. That usage is very common, including in biomechanical references. The forearm rotation direction is toward the the same positions as shown in the video above so this usage is closely related to the anatomical definition of #1. You might search and find on the internet, maybe not. If you think this usage is defined please search and provide some links.

3) Tennis Usage of 'Pronation'. The term is broadly used for the considerable arm rotation that can be seen by eye at the wrist especially at the end of the follow through. This motion in the follow through is mostly pronation (the rotation usage of #2). Leading up to impact, however, there is very little forearm pronation but a lot of internal shoulder rotation (ISR) to provide the largest component of racket head speed. The tennis usage of the term 'pronation' can not be searched on the internet. A dinosaur from the 1970s when people looked at tennis strokes by eye .....I even head Elliott use 'pronation' after his research and publications explained ISR. Since pronation is not a good term for the ISR of the serve you can't search and find an internet definition to describe how it is being used - its only in the collective tennis wisdom of....

There is a conflict if you think about the definition of #1 and the common usage of #2. If the angle of the forearm as defined is, say, in a position of 40 of supination but the forearm is rotating in the direction of pronation- are we sure what everybody means by pronation or supination?

Note-

"The Anatomical Position" - in this position all joints of the body are in their reference positions including supination and pronation at 0.
https://www.google.com/search?q=anat...w=1334&bih=722
IMO we can say that the wrist is in maximum extension position (or minimum flexion position) when it has angle -90. Similarly, the wrist is in maximum flexion position (or minimum extension position) when the angle is +90. Start point of motion can be arbitrary within the range from -90 to +90. So, according to proper definitions of these motions I can use the term wrist flexion to describe the wrist unbending progression.
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