Help with muscle kinesiology?!?

[Mlewis904]

I understand when doing a yoga pose you are putting certain muscles into "greatest stretch", but what does it mean when you're asked which muscles are being put into "greatest ease"? Does that mean the muscles being contracted? So confused!

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[aggiecjg11]

I think this is a question of active vs. passive insufficiency. The way that I learned it was in active insufficiency, the muscle is put on a "slack", and Kendall describes it as when a 2-joint muscle cannot generate an effective force when put into a shortened position. An example we used for this is full elbow flexion with full shoulder flexion. Passive insufficiency, according to Kendall, is when the length of the 2-joint muscle is not sufficient to permit normal elongation over both joints simultaneously, like the biceps femoris during knee extension and hip flexion. So this might be what your instructor means when he or she talks about "greatest stretch" and "greatest ease". I would think that in the "greatest ease" (active insufficiency) the muscle is contracted as much as it will go to where it can't produce any more force or contract any further. Hopefully this helped answer your question, and if I'm wrong, someone please correct me!

 

[A Burly Man]

Passive insufficiency, according to Kendall, is when the length of the 2-joint muscle is not sufficient to permit normal elongation over both joints simultaneously, like the rectus femoris during knee extension and hip flexion.

I like the explanation.

 

[Akiramay]

I like the explanation.

Biceps femoris is correct. The hamstring cannot be elongated enough to achieve full knee extension and hip flexion...hence passive insufficiency.