VISCOPLASTICITY OF RABBIT SKELETAL-MUSCLE UNDER DYNAMIC CYCLIC LOADING

To elucidate the strain effects of dynamic cyclic loading on the skeletal muscle-tendon unit, the muscle-tendon unit of New Zealand white rabbits were tested with different strains and strain rates under ketamine general anaesthesia. The results indicated that the dynamic responses of muscular tissues were both strain and strain-rate dependent with appreciably non-linear characteristic. The muscle-tendon unit behaved viscoelastically below 12% strain; but when stretching more than 16% strain it began to behave plastically. The loading energies and unloading energy are more dependent on strain than on strain-rate. Relevance This study offers firm evidence that plasticity may be one of the important biomechanical properties of the skeletal muscle. The findings in this report imply that the expression of skeletal muscle mechanical behaviour may not be limited to phenomena represented by a composition of elastic and viscous elements. The elongation of skeletal muscle under sustained stretching might be explained by the plastic property. Elucidation of the existence of viscoplasticity in skeletal muscle gives a good reference point to determine the functional capabilities and limitation of muscular tissue.