| Background: Temporal Interference Electrical Fields(TI)is a novel Non-invasive Brain Stimulation(NIBS)technique.It utilizes the characteristic that nerve cells do not react to electric fields with frequencies higher than 1k Hz.When two electric fields E1 and E2 with different frequencies above 1k Hz were transported to the brain,nerve cells will not react in theory because of high frequency,the superposition of the two alternating currents stimulated by TI will generate envelope waves in the deep part of the brain,which can stimulate nerve cells in the deep region of the brain,which has more advantages than traditional transcranial electrical stimulation.In this study,multi-session TI stimulation was applied to the lower limb motor cortex to explore the influence on longitudinal jump and balance,as well as the influence on lower limb motor ability.Methods: In this study,40 subjects were randomly divided into TI stimulation group and sham stimulation group using a randomized double-blind parallel control design.The target area of TI stimulation parameter was lower limb motor cortex,and its electrodes were placed in F3,P3,F4 and P4.F3 and P3 are one current,and F4 and P4 are another one.The frequencies of the two channels are 2000 Hz and 2020 Hz respectively,and the current intensity is 2m A.The envelope wave of 20 Hz is generated in the target area.The intervention period was 5 days,2 times a day(20-minute interval),and the duration of each stimulation was 20 minutes.The sham stimulation parameter had the same current intensity,frequency and electrode placement as TI stimulation,but only included fading in and out for 30 s.The day before the intervention and the day after the intervention,subjects’ dynamic data during Counter movement jump(CMJ)and Squat jump(SJ),vertical jump height of Continuous jump(CJ),and EMG data were collected.And evaluate its dynamic balance ability.Two-Way Repeated ANOVA of variance was used to analyze the effects of TI stimulation on vertical jump ability and balance ability.When interaction effect is significant a post hoc analysis is required.Results: 1)Vertical jump ability: The vertical jump height of CMJ and SJ increased after TI stimulation intervention,and the jump height of SJ had significant interaction effect(p=0.017)and time main effect(p=0.014).Post test showed that the jump height increased significantly after TI stimulation intervention(p=0.012),increasing by 7.5%.The peak power of CMJ increased after TI stimulation and sham.TI stimulation increased significantly after intervention(p=0.006).There were no significant differences in reaction force,impulse,fatigue index and slope after TI stimulation and sham.2)Balance ability: the anteroposterior moving distance did not change after TI stimulation and sham;the poster posterior moving distance increased after TI stimulation and sham,and showed a significant increase after TI stimulation(p=0.007);After the intervention of TI stimulation,the movement distance in the posterolateral direction did not change,but increased after the intervention of sham.Conclusion: This study proves that TI stimulation on lower limb motor cortex has certain modulation effect on lower limb motor ability of healthy adults,especially jump height and peak power.This evidence will help promote the research and application of TI stimulation in deep brain region,and provide safety and feasibility support for the setting and optimization of TI in deep brain stimulation program. |
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