Effects Of Transcranial Direct Current Stimulation On Upper Limb Strength,Muscle Activity And Motor Cortex Excitability

Background:Transcranial direct current stimulation(tDCS)is a non-invasive brain stimulation technique that regulates the excitability of a particular brain region and,in turn,affects the ability of the body to perform weak direct current stimulation of a particular brain region by electrodes placed on the scalp.In this study,the right elbow flexion and extensor muscle group of healthy men before and after intervention were tested with different tDCS stimulation methods to explore the effects of tDCS on muscle strength output,muscle activity and motor cortex excitability in healthy men with electrophysiological technology,to provide some research basis for the application of tDCS technology to exercise training.Method:16 healthy men(age:24.4±1.9yrs,height:173.3±6.0cm,weight:68.7±10.3kg),using repetitive-blind test,each subject was subjected to three different modes of tDCS intervention in three different time periods,before and after each intervention using CON-TREX isokinetic force measurement system and electromyography system to measure the muscle strength and EMG signal of flexion and extension of flexion and extension muscle group in the upper elbow joint of the right limb;In addition,eight of the subjects used TMS for subsequent motor cortical excitability tests,and the experimental design was the same as above.Result:(1)Muscle force: There was no significant difference between the three intervention modes.The difference in the group was that the peak torque and peak power of Sham-tDCS group decreased significantly and that peak power of C-tDCS group decreased significantly,C-tDCS and Sham-tDCS were significantly reduced at 180°/s,only C-tDCS was significantly reduced after intervention at 60°/s;For the force output change index,the peak torque change rate of flexor elbow was significantly smaller than that of Sham-tDCS group after A-tDCS stimulation at a high speed of 180°/s(3.7±1.9% vs.-4.6±2.4%,P<0.05),the change rate of peak flexor power after intervention in A-tDCS group was significantly smaller than that in C-tDCS group and Sham-tDCS group(6±4.5%,-11.6±2.8%,-7.3±2.5%;P<0.05),The rate of change of total work done in A-tDCS group was also significantly smaller than that in C-tDCS group and Sham-tDCS group(1.36±3.5%,-7.6±2.6%,-7.7±2.7%;P<0.05);(2)Muscular activity: The three intervention modes did not significantly affect the activation levels of biceps and triceps as active or antagonistic muscle.However,for the antagonistic muscle co-activation ratio,the A-tDCS group had a less tendency than before the intervention at the high speed of 180°/s isokinetic flexion(P<0.1).(3)Motor cortex excitability: The amplitude of MEP was significantly higher than that of baseline after intervention in A-tDCS group,and that in C-tDCS group was significantly lower than that of baseline group.There was no significant difference between A-tDCS group and Sham-tDCS group(P =0.34).Conclusion:Anode transcranial direct current stimulation instantly increased the excitability of the motor cortex,and had a positive effect on muscle fatigue resistance and maintenance of high-intensity work ability,but the gain effect on maximum strength was not significant.The cathodic intervention has a negative effect on the excitability of the cortex and the motor performance of the muscle.this study suggests that this neuroregulatory technique can be used as a new type of sports training aid,which is selected to be used in fast force dominated sports and items that need to maintain high power output.