[Yoda]

Muscles cannot develop a force concentrically, isometrically, or eccentrically at the same time. Muscles can only develop a force one way at a time, so if and when the triceps fibers shorten to move the left arm, extensor action (which supposedly does not move the left arm) can no longer be in effect. The triceps or any other muscle just isn't talented enough to develop dual or treble forces wherein the same fibers would have to independently and simultaneously contract, lengthen, and/or remain the same length.

Coophitter

Thanks for your post, Coop. Have you tried my 'Armless Sleeve' drill posted earlier today (#86 in this thread), especially the Hitter's application? If so, I would appreciate your thoughts.