DYNAMIC VISCO-ELASTIC PROPERTIES OF GLYCEROL-EXTRACTED MUSCLE FIBERS

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Abstract
The dynamic stiffness increases during contraction and decreases during relaxation. The stiffness-tension relation is linear in most parts of either contraction or relaxation processes, and their tangents are almost equal to each other. When the sinusoidal changes in length (peak to peak) are less than 1.5 per cent of muscle length, the fiber''s obey Hook''s law. The complex modulus measured at frequencies of 20 or 40 c/sec of contracted muscle is 7000 or 10000 g wt.cm-2. The modulus is decreased to 800 or 1200 g wt.cm-2 if the muscle is relaxed in 100 mM pyro-phosphate-Na solution or 1 MKC1 solution, and to 2000 g wt.cm-2 in 50 mM pyrophosphate-Na solution containing 2 mM MgCl2. Elastic modulus and viscosity calculations are based on the Theological analysis. The retardation time is 0.8 or 2.0 msec. When the muscle is stretched, the stiffness is always increased. From the time course of decay of tension after quick stretch, it is suggested that there might be another system with a time constant of a few seconds. Visco-elastic properties and their changes in the contraction process of glycerol-extracted muscle are similar to those of living muscle.
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