The mechanical effect of ultrasound on passive muscle force based on the standard linear solid model

Passive muscle force adversely affects joint movement and the motion control system. Relaxing passive muscle force can substantially improve movement impairment and also relieve muscle pain and cramping caused by high-intensity exercise. We intended to study the effect of ultrasound on passive muscle force relaxation. The results showed that the passive force of the specimens in the ultrasound group decreased by 21.9% compared with the initial value. Experimental data were fitted and analyzed using the standard linear solid model of biological tissue—the viscosity coefficient and elastic coefficient of the model group were higher than those of the control group, and the relaxation time increased significantly. We propose that ultrasonic mechanical stimulation can change the viscoelasticity of muscle and decrease passive muscle force, which provides an important theoretical basis for research on the effect of ultrasound on muscle tissue, its use in the treatment of disease and in the rehabilitation of function, and new methods of maintaining muscle function.