| Purpose: In order to investigate the neurophysiological mechanisms behind the effect of tDCS on the regulation of incremental cycling,and to find the brain areas where tDCS can better enhance the performance of incremental cycling,this study used functional near-infrared spectroscopy(fNIRS)to monitor brain activation during incremental cycling in healthy adults and to tailor the tDCS protocol to enhance the performance of incremental cycling based on the activation characteristics of the brain during fatigue,and to investigate the performance-enhancing effect of the protocol.Methods: Seventy healthy college students(Study 1: 30,age: 23.73±3.60 years,height: 170.23±6.71 cm,weight: 63.33±15.23 kg;Study 2: 40 subjects,age:22.65±2.42 years,height: 174.43±4.66 cm,weight: 71.11±9.92 kg)participated in this experiment.In Study 1,subjects completed a multi-level incremental load cycling test monitored by functional near-infrared brain imaging and a tDCS protocol tailored to incremental load cycling based on brain activation characteristics during fatigue,and the relationship between activation channels during fatigue was analyzed by Pearson correlation analysis;in Study 2 were divided into anodal group(active transcranial direct current stimulation,a-tDCS)and sham stimulation group(sham transcranial direct current stimulation,sham-tDCS)according to a randomized,double-blind,parallel-controlled design,and received a single customized anodal tDCS intervention and sham stimulation,respectively.Two-factor ANOVA was used to assess the effects of different stimulation modalities on cycling performance before and after the intervention;paired-samples t-test was used to analyze the differences in cycling performance before and after the intervention.Results:(1)Brain activation status: multiple channels were activated during fatigue,with significantly lower beta values of Oxy-Hb concentrations in channels 25,28,38 and 39 and significant correlation with multiple channels(p<0.05);(2)Customized tDCS protocol: Based on the activation characteristics of the brain during fatigue,the target brain areas were finally identified as premotor area,supplementary motor area,primary motor area and frontal eye,and the specific placement of electrodes were: C1,C2,FC1,FC2,AF7,P9,PO7;(3)Validation of the effect of the customized protocol:There were no significant effects of the two stimulation modalities on cycling duration,cycling performance-related indexes,heart rate at fatigue,post-exercise blood lactate value and subjective rate of perceived exertion(RPE).Conclusion: Brain activation during multi-level incremental load cycling in healthy adults was explored by fNIRS,and the tDCS protocol was customized and validated based on brain activation characteristics during fatigue.The results showed that a single a-tDCS intervention of this customized protocol did not produce a modulatory effect on incremental load cycling performance.The results of the study can provide a reference for the development of tDCS protocols and provide a theoretical basis for the modulatory effect of such customized tDCS protocols on incremental load cycling performance.In the future,we may consider monitoring the activation status of subjects during exercise by TMS or fNIRS,and then further develop individualized tDCS energizing protocols according to the specific activation characteristics of the subjects. |
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