A Preliminary Study On The Effect Of Low-intensity Pulsed Ultrasound On Skeletal Muscles

Skeletal muscle is an important organ for posture maintenance and motion control.Under the condition of muscle fatigue,injury or disease,if we continue to exercise unscientifically or not deal with it in time,it may cause more serious injury,fracture and even stress fracture of muscle fibers,which seriously affects people's daily life or the effect of physical training.Therefore,muscle tissue injury and functional recovery of pathological changes may occur.Re-diagnosis and treatment have important practical significance for human health and normal life.In order to investigate the biological effects of ultrasound in muscle tissue,the biological effects of low-intensity pulsed ultrasound were studied from the characteristics of ultrasound transmission in muscle tissue,and the effects of low-intensity pulsed ultrasound on the muscle strength of gastrocnemius muscle in SD rats during continuous passive vibration were discussed.The solid state of various human tissues consisting of epidermis,fat,muscle and bone was studied.The thermal effects of low-intensity pulsed ultrasound and low-intensity focused ultrasound provide theoretical basis for the application of ultrasound in muscle tissue.The main contents include:(1)The mechanical properties of muscle fibers are studied by finite-difference time-domain method,and the natural frequencies of muscle fibers and the vibration modes at corresponding frequencies are discussed.The effects of low intensity pulsed ultrasound on gastrocnemius muscle of SD rats were studied.The changes of muscle strength with ultrasound and its mechanical effects were studied.To study the relationship between the changes of gastrocnemius muscle strength and external ultrasound in SD rats after tibial nerve stimulation at different frequencies and constant current intensity.The theoretical and experimental results show that,when there is no ultrasound effect,the non-linear increase of muscle force between 30Hz and 70Hz and decrease between 70Hz and 110Hz,and the maximum value of muscle force is reached at 70Hz.Although there are differences in muscle strength between different individuals,the general rule is the same.After ultrasound treatment,the decline rate of muscle strength was significantly reduced,and the percentage of the decline rate of muscle strength at 30 Hz,50 Hz,70 Hz,90 Hz and 110 Hz frequencies was 41.64%,37.11%,36.84%,27.77%and 34.90%,respectively.From the results,low intensity pulsed ultrasound reduced the decline rate of muscle strength after the gastrocnemius muscle was exposed,which indicated that ultrasound had a significant mitigation effect on the decline of muscle strength in the process of continuous muscle vibration.(2)Temperature effects of low intensity pulsed ultrasound and low intensity pulsed focused ultrasound in multiple human tissues were studied.Within a reasonable range of ultrasound parameters,low intensity pulsed ultrasound can cause less effective temperature rise and less possibility of thermal effect.Low intensity focused ultrasound can cause effective tissue warming at the focal point.It is necessary to avoid this kind of thermal effect for diagnosis.As a potential biological mechanism of thermal effect of biological therapy or muscle function recovery,it is worth further study.We have studied the relationship between ultrasonic stimulation parameters and thermal effect:with the stimulation sound pressure,central frequency and duty cycle.With the increase of fat thickness,the temperature of the focus position decreases.