INTERFACE TENSION THEORY OF MUSCULAR CONTRACTION.
Research communication no. 10,
DOUGLAS AIRCRAFT CO INC HUNTINGTON BEACH CALIF ADVANCED RESEARCH LAB
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The purpose of this theoretical study is to identify and explain the fundamental source of the forces that cause filament sliding and tension generation during muscular contraction. This paper considers the interface tension in the interface phase of the myoplasmic fluid at the actin and myosin filament boundaries. Because of the geometrical arrangement of the filaments and the localized chemical reactions that are known to take place, gradients occur in the interface tension which cause molecules in the interface phase of the myoplasmic fluid to move parallel to the filaments. The motion at the interface causes viscous shearing in the myoplasmic fluid, which balances the gradient in tension. It is shown that the forces that cause filament sliding and muscular load are the reactions to the viscous shear stresses in the myoplasmic fluid between the overlapping filaments. The velocity of the molecules in the interface phase with respect to the filament is expected to be less than five microns per second, even at maximum physiological effort. This velocity is compatible with motion in close proximity to the solid filaments. This study unexpectedly showed that the contractile load is carried by the myoplasmic fluid interfaces rather than by the filaments themselves. The stresses in the filaments are always compressive, being in a lower state of compression when the muscle is generating force. Author
- Anatomy and Physiology