VISCOPLASTICITY OF RABBIT SKELETAL-MUSCLE UNDER DYNAMIC CYCLIC LOADING

To elucidate the strain effects of dynamic cyclic loading on the skele tal muscle-tendon unit, the muscle-tendon unit of New Zealand white ra bbits were tested with different strains and strain rates under ketami ne general anaesthesia. The results indicated that the dynamic respons es 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 unload ing energy are more dependent on strain than on strain-rate. Relevance This study offers firm evidence that plasticity may be one of the imp ortant biomechanical properties of the skeletal muscle. The findings i n 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 un der sustained stretching might be explained by the plastic property. E lucidation of the existence of viscoplasticity in skeletal muscle give s a good reference point to determine the functional capabilities and limitation of muscular tissue.