Effects Of Different Durations Of Transcranial Direct Current Stimulation On Exercise Capacity In Elite Male Volleyball Players

Obejective:Transcranial direct current stimulation（t DCS）is a low-cost,non-invasive brain stimulation method that is used to modulate cortical excitability by applying low-intensity direct current to the scalp,overlying a target region of the brain,with surface electrodes connected to a controlled current-generating unit.t DCS has recently been used for improving exercise performance of athletes during competition and training.However,it is still unknown that the effects of t DCS on exercise performance in volleyball players.Moreover,it remains to be clarified whether extending the stimulation time further improve the ergogenic effects of t DCS.Therefore,the aim of the present study was to investigate the effects of different duration of t DCS on vertical jump ability,agility test and the ball velocity in elite volleyball players.Methods:In this single-blind,randomized,sham-controlled study,twelve male volleyball players received a placebo stimulation（Sham）,15 min（t DCS15）or 30 min（t DCS30）anode t DCS intervention.The current intensity of t DCS15 and t DCS30was 2 m A.At the end of the t DCS session,the subjects performed a 10-min warm-up,then performed the following volleyball-specific tests:countermovement jump（CMJ）,squat jump（SJ）,the agility Eurofit 10×5-m shuttle run test（SRT）,the agility-half“米”test,the standing spike ball velocity.The session rating of perceived exertion（s RPE）was estimated 20 min post-exercise.Alterations in the CMJ height,the SJ height,SRT,the half“米”test,the standing spike ball velocity and SRPE values were subjected to one-way analysis of variance（ANOVA）.If significant main effects were found,post-hoc analyses were carried out with a Bonferroni correction.Statistical significance was accepted at P<0.05.Results:（1）Vertical jump ability:The vertical jump height of the SJ in the t DCS15 group was significantly higher than that in the Sham（Sham:0.39±0.07 m,t DCS15:0.46±0.08m,P<0.05）.The vertical jump height of the SJ in the t DCS30 group was significantly higher than that in the Sham（Sham:0.39±0.07 m,t DCS30:0.46±0.07 m,P<0.05）.There was no significant difference in SJ vertical jump height between t DCS15 and t DCS30 groups.However,no difference of CMJ height was observed among the three groups（F=1.91,P=0.165,ηp₂=0.101）.（2）Agility:The running time of the"half-米"in the t DCS15 group was significantly shorter than that in the Sham（Sham:15.81±0.62 s,t DCS15:15.26±0.61 s,P<0.05）.The"half-米"running time of the t DCS30 group was significantly shorter than that in the Sham（Sham:15.81±0.62 s,t DCS30:15.18±0.52 s,P<0.05）.There was no significant difference in"half-米"running time between t DCS15 and t DCS30groups.However,no difference of the shuttle run test was observed among the three groups（F=0.22,P=0.808,ηp₂=0.013）.（3）Ball velocity:The ball speed of the t DCS15 group was significantly faster than the Sham group（Sham:48.00±3.10 mph,t DCS15:50.75±2.96 mph,P<0.05）.The ball speed of the t DCS30 group was significantly faster than the Sham group（Sham:48.00±3.10 mph,t DCS30:50.67±2.64 mph,P<0.05）.However,there was no significant difference in ball speed between t DCS15 and t DCS30 groups.（4）SRPE:SRPE was significantly different among the three groups（F=15.37,P=0.0001,ηp2=0.506）.SRPE in the t DCS15 was significantly lower than that in the Sham（Sham:6.73±0.79,t DCS15:5.09±0.83,P<0.05）,SRPE in the t DCS30 was also significantly lower than that in the Sham（Sham:6.73±0.79,t DCS30:5.28±0.65 mph,P<0.05）,but these was no significance of SRPE between t DCS15 and t DCS30.Conclusion:These results suggest that t DCS can improve physical performance in male volleyball players,but it is not necessary to prolong the stimulation duration for enhancing t DCS effects.