[Dissipative processes in human passive skeletal muscle]

The measurement of damping of low-amplitude limb oscillations permits to evaluate the energy losses in passive human skeletal muscle during small length changes. The attenuation curve for the limb oscillations is quite different from the classical attenuation curve in the presence of viscous damping. Energy losses per oscillation cycle are practically frequency independent. Thus the damping properties of passive muscles at joint angular velocities up to 100% are due mostly to the velocity-independent resistance of "dry friction" type. The value of this "friction" is about 0.07 N per sm2 of muscle cross-section. The passive muscle also has marked thixotropy, as its resistance to small amplitude low velocity stretches strongly depends on time between stretches.