[hcw]

hcw said..." I think that if you have lots of tension in the muscles of the arms, then you can use them very well to swing"

I think what you are saying could work, but probably better for a Hitter.
6-B-1-D-- Extensor Action-- "This stretches but does not move the Left Arm"

I heard Extensor Action once described as... "extension without tension"

There are probably also different TYPES of tension. A feeling of being athletic, confident, and ready to produce a dynamic stroke, is different than tension that is induced through anxiety, apprehension, nervousness, or poor technique or concepts.

When you get that confident, athletic, FEELING, and are producing quality shots, then you are on to something. This probably feels a little different for everyone.

lagster,
i have not totally figured out what is meant by "Extensor Action" and i don't have the book handy, so i'll leave that for the more knowledgable....the second thing you are describing i think is what is called muscle "tone"...your muscles can run a spectrum from totally relaxed/flaccid to totally tense/contracted...to be useful they need to be somewhere in between and indeed there needs to be some baseline "tone", a little contraction that can be increased or decreased depending on the task at hand...in fact decreased tone can be sign of a problem (ie disease state) as can increased...the condition you descibed where:

"TENSION is introduced into the player during the swing, especially IN THE ARMS during the downswing, the player will be taken out of his CORE, and strike the ball ONLY utilizing the weight of his arms, rather than the MASS of his entire body."

...doesn't make sense to me, as i don't think the body's mass hits the ball...the analogy doesn't work for me, so i rethink it as describing too much tension/contraction in the arms which doesn't allow them to be "athletic, confident, and ready to produce a dynamic stroke"...but if the image works for you (meaning anybody) that's great...i totally agree that all of "This probably feels a little different for everyone.'" and that's why Bobby Jones responded to the question of "Can you show me how to swing?" on one of those instructional films saying that "I can show you the basics, but you'll have to work out the details for yourself"

-hcw