Question for Will Hamilton (& others who promote laid back wrist on forehand contact)

[toly]

Originally Posted by Chas Tennis

I don't know much about EMG measurements but maybe, in principle, that kind of research can answer questions about the muscle tension & activation timing.

Search - EMG forehand tennis, etc.

For example, the forehand is mentioned briefly in this reference, page 305.

http://books.google.com/books?id=-Gy...tennis&f=false

I’m retired Electrical Engineer and really don’t know anything about muscles. Nevertheless, I found interesting information (?) in the article you posted http://books.google.com/books?id=-Gy...tennis&f=false, page 305.

There is citation:

“The golf swing may be divided into four specific phases: take-away, forward swing, acceleration, and follow-through. During the take-away phase, the wrist flexors exhibit minimal EMG activity, whereas the wrist extensors exhibit 33% of a maximum voluntary isometric contraction (MVIC). The forward swing is characterized by increased muscle activity of both the wrist extensors, which exhibit 45% MVIC, and the wrist flexors, which exhibit 35% MVIC. At ball contact, the wrist flexors activity significantly increases to 91% MVIC. …

Results of a study of the muscular activity pattern of golfers with medial epicondylitis and golfers with no injury indicated significantly greater wrist flexor muscles activity in the golfers with medial epicondylitis during the take-away, forward swing, and acceleration phases.”

I have problem with English and cannot understand clearly above statements.

Does it mean that the wrist flexion must be almost maximally (91%) active at ball contact??????????

[5263]

Originally Posted by toly

Does it mean that the wrist flexion must be almost maximally (91%) active at ball contact??????????[/size][/b]

I don't think so.
I think it means the wrist extensors are giving a 91% effort.
I don't think we know if that effort is to stabilize the stroke or flexion.
Does look good for your point of view on the surface of things I suppose.

[Chas Tennis]

Originally Posted by toly

...........................................
Does it mean that the wrist flexion must be almost maximally (91%) active at ball contact??????????

I don't know how to interpret the EMG information but from time to time I see publications that show EMG measurents. I believe that I have seen one on forehands or serves.

Probably the EMG activity would be high for

1) high acceleration joint movement, flexion or extension, etc.
2) isometric type non-movement where the agonist muscle and its antagonist are both activated. No joint flexion or extension, etc.
3) when the joint itself is being accelerated by larger body parts and the muscle must be activated simply to keep the joint in the same degree of flexion or extension, etc..or to limit motion.
4) gripping a racket with no joint movement.

Probably no EMG activation is required to stretch a muscle. If the muscle has been pre-stretched I would think that it might contract very rapidly without EMG activation.?

EMG interpretation is a complicated subject. Does anyone have a readable reference to include EMG interpretation?

[pushing_wins]

whats going on here? are you guys saying its flexion?

[5263]

Originally Posted by pushing_wins

whats going on here? are you guys saying its flexion?

Not most posters

[Chas Tennis]

BTW - Update regarding EMG and muscle force-

A biomechanics researcher answered my question - EMG activation does not accompany muscle shortening that is supplied by the pre-stretched passive muscle component.

This is important in biomechanics because the passive muscle component is described as being able to supply forces at higher muscle shortening velocities.

I'm trying to interpret and understand this biomechanics principle (which I may have misstated). The issue is most clearly considered using the Hill Muscle Model description or similar model.

I currently think it means that the highest velocities in athletics are probably supplied by passive pre-stretched muscles. ??

It's too bad biomechanics researchers never play tennis and use this stuff........

[Anton]

Originally Posted by Chas Tennis

BTW - Update regarding EMG and muscle force-

A biomechanics researcher answered my question - EMG activation does not accompany muscle shortening that is supplied by the pre-stretched passive muscle component.

This is important in biomechanics because the passive muscle component is described as being able to supply forces at higher muscle shortening velocities.

I'm trying to interpret and understand this biomechanics principle (which I may have misstated). The issue is most clearly considered using the Hill Muscle Model description or similar model.

I currently think it means that the highest velocities in athletics are probably supplied by passive pre-stretched muscles. ??

It's too bad biomechanics researchers never play tennis and use this stuff........

That has been my view on wrist action - relaxed wrist maximizes racket head speed with very low effort (assuming proper set up and tension build up).

[pushing_wins]

so whats the latest on the wrist deviation theory?