Effects Of Temporal Interference Stimulation On Muscle Strength And Neuromuscular Recruitment

Objective: Temporal interference(TI)stimulation is a new non-invasive deep brain stimulation technology,which transmits two electric fields with slightly different frequencies in the k Hz range to the brain,these two electric fields can form low-frequency envelope waves in the deep brain region to stimulate the activity of neurons in selected regions.Some studies have verified the effectiveness of TI stimulation in mouse experiments.Other studies have proposed the feasible stimulation scheme of TI stimulation in human experiments through simulation and calculation,but the mechanism of TI stimulation is still unknown,and the best stimulation scheme still needs to be explored.This study aims to explore the effects of TI stimulation on muscle strength and neuromuscular recruitment,and provide a theoretical basis for the application of TI in human experiments in the future.Methods: This study was a randomized,double-blind and controlled experiment.Subjects received TI stimulation or sham stimulation at random in two follow-up visits,with an interval of more than 48 hours,and completed the first dorsal interosseous(FDI)muscle strength and EMG test.The parameters of TI stimulation include: the peak to peak current of each AC circuit is 4m A,the frequency of low-frequency envelope wave is variable frequency(5、10、20、40Hz),and the stimulation duration is 20 min.The stimulating area is the left motor cortex(M1).According to the international 10-20 EEG system,electrodes are placed at C1,C5,F1 and F5.Two factor repeated measurement analysis of variance was used to study the effects of TI stimulation on muscle strength,force generation rate,muscle strength attenuation rate,number of motor units,average discharge rate and peak EMG amplitude.Results: All subjects completed the intervention,the blinding effect was good,the percentage of reported TI side effects was small,and no serious adverse reactions were reported.Two factor analysis of variance showed that the interaction of time and stimulation mode had significant effects on the maximum muscle strength of 3s MVC and the peak EMG amplitude of 20 s MVC(P <0.05).After TI stimulation,the maximum muscle strength of 3s MVC increased by 2.1%,and the peak EMG amplitude of 20 s MVC increased by 28.2%;After sham stimulation,the maximum muscle strength of 3s MVC decreased by 3.6%,and the peak EMG amplitude of20 s MVC decreased by 9.3%.Statistical analysis showed that TI stimulation had no significant effect on the muscle strength attenuation rate,average EMG amplitude,discharge rate and force generation rate.Conclusion: This study explored the effects of TI stimulation on muscle strength and neuromuscular recruitment for the first time.The results of this study show that TI stimulation can improve human muscle strength 、 optimize neuromuscular recruitment and provide evidence of the safety and feasibility of TI stimulation in human experiments.Therefore,TI stimulation may be a promising non-invasive brain stimulation technology and a potential method to improve muscle strength and promote motor performance.In the future,based on the existing research,we should constantly adjust the electrode position,current intensity and frequency in order to obtain the best human brain TI stimulation mode.