***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Transcranial direct current stimulation ( tDCS ) of the human motor cortex results in polarity-specific shifts of cortical excitability during and after stimulation . Anodal tDCS enhances and cathodal stimulation reduces excitability . Animal experiments have demonstrated that the effect of anodal tDCS is caused by neuronal depolarisation , while cathodal tDCS hyperpolarises cortical neurones . However , not much is known about the ion channels and receptors involved in these effects . Thus , the impact of the sodium channel blocker carbamazepine , the calcium channel blocker flunarizine and the NMDA receptor antagonist dextromethorphane on tDCS-elicited motor cortical excitability changes of healthy human subjects were tested . tDCS- protocol s inducing excitability alterations ( 1 ) only during tDCS and ( 2 ) eliciting long-lasting after-effects were applied after drug administration . Carbamazepine selectively eliminated the excitability enhancement induced by anodal stimulation during and after tDCS . Flunarizine result ed in similar changes . Antagonising NMDA receptors did not alter current-generated excitability changes during a short stimulation , which elicits no after-effects , but prevented the induction of long-lasting after-effects independent of their direction . These results suggest that , like in other animals , cortical excitability shifts induced during tDCS in humans also depend on membrane polarisation , thus modulating the conductance of sodium and calcium channels . Moreover , they suggest that the after-effects may be NMDA receptor dependent . Since NMDA receptors are involved in neuroplastic changes , the results suggest a possible application of tDCS in the modulation or induction of these processes in a clinical setting . The selective elimination of tDCS-driven excitability enhancements by carbamazepine proposes a role for this drug in focussing the effects of cathodal tDCS , which may have important future clinical applications The aim of this study was to investigate the effects of transcranial direct current stimulation ( tDCS ) on countermovement jump performance ( CMJ ) in men with advanced strength training experience . Ten healthy male subjects , with advanced strength training and squatting exercise experience , were included . Participants took part in an initial visit to the laboratory to complete anthropometric measurements and CMJ kinematic test-retest reliability . Participants then completed three experimental conditions , 48 - 72 hours apart , in a r and omized , double-blinded crossover design : anodal , cathodal and sham tDCS ( 2 mA for 20 minutes targeting the motor cortex bilaterally ) . Participants completed three CMJ tests  before and after each experimental condition , with one-minute recovery interval between each test . The best CMJ in each moment was selected for analysis . Two-way ( condition by moment ) repeated measures ANOVA 's were performed for CMJ height , flight time and muscular peak power . Effect sizes and interindividual variability of tDCS responses were also analyzed . There was a significant condition by moment interaction for all outcome measures , with a large pre-post increase in CMJ height , flight time and muscular peak power in the anodal condition . All the participants displayed CMJ performance improvements after the anodal condition . There were no significant differences in both cathodal and sham conditions . Anodal tDCS may be a valuable tool to enhance muscle power related tasks performance , which is extremely relevant for sports that require vertical jumping ability . Anodal tDCS may also be used to support strength training , enhancing its effects on performance-oriented outcome measures Anodal transcranial direct current stimulation ( tDCS ) is known to increase the force-generating capacity of the skeletal muscles . However , when tDCS is concurrently combined with a motor task , interference may occur that hinders tDCS effects . Here , we tested the interaction and time course of tDCS effects on force production when paired with a low-level force-matching task . Twenty-two subjects were r and omized into two groups : tDCS-Matching and tDCS-Resting . Each group received tDCS and a sham stimulation , separated by one week . Maximal knee extensor and flexor torques were measured before and up to twenty-five minutes following the stimulation . The tDCS-Matching group produced greater knee extension torques relative to sham when compared with the tDCS-Resting group . There was no significant effect for knee flexion . This suggests that interference does not occur for force production tasks when tDCS is combined with a motor task . Rather , the task appears to aid and isolate the effects to the muscle groups involved in the task BACKGROUND Decreased cortical excitability has been proposed as a potential mechanism underlying task failure during sustained muscular contractions , and cortical excitability may decrease with old age . We tested the hypothesis that transcranial direct current stimulation , which has been reported to raise cortical excitability , would prolong the time to task failure during a sustained muscular contraction in older adults . METHODS Thirteen older adults ( 68.3±2.0 years ; eight women and five men ) performed isometric , elbow flexions to failure while receiving sham or anodal transcranial direct current stimulation . Order of stimulation was r and omized , and the subjects and investigators were blinded to condition . Time to task failure was measured alongside selected psychological indices of perceived exertion and affect . RESULTS Anodal transcranial direct current stimulation  prolonged mean time to task failure by approximately 15 % ( 16.9±2.2 vs 14.7±1.8 minutes ) and slowed the rate of increase in rating of perceived exertion ( 0.29±0.03 vs 0.31±0.03 ) relative to the sham condition . CONCLUSIONS These preliminary findings suggest that anodal transcranial direct current stimulation  enhances time to task failure of a sustained , submaximal contraction in older adults by potentially increasing cortical excitability and /or influencing the perception of exertion . These results raise the question of whether interventions that acutely increase cortical excitability could enhance physical function and /or exercise-induced adaptations in older adults The purpose of this study was to determine whether anodal transcranial direct current stimulation ( tDCS ) delivered while performing a sustained submaximal contraction would increase time to task failure ( TTF ) compared to sham stimulation .  Healthy volunteers ( n = 18 ) performed two fatiguing contractions at 20 % of maximum strength with the elbow flexors on separate occasions . During fatigue task performance , either anodal or sham stimulation was delivered to the motor cortex for up to 20 minutes . Transcranial magnetic stimulation ( TMS ) was used to assess changes in cortical excitability during stimulation . There was no systematic effect of the anodal tDCS stimulation on TTF for the entire subject set ( n = 18 ; p = 0.64 ) . Accordingly , a posteriori subjects were divided into two tDCS-time groups : Full-Time ( n = 8) , where TTF occurred prior to the termination of tDCS , and Part-Time ( n = 10 ) , where TTF extended after tDCS terminated . The TTF for the Full-Time group was 31 % longer with anodal tDCS compared to sham ( p = 0.04 ) , whereas TTF for the Part-Time group did not differ ( p = 0.81 ) . Therefore , the remainder of our analysis addressed the Full-Time group . With anodal tDCS , the amount of muscle fatigue was 6 % greater at task failure ( p = 0.05 ) and the amount of time the Full-Time group performed the task at an RPE between 8–10 ( “ very hard ” ) increased by 38 % ( p = 0.04 ) compared to sham . There was no difference in measures of cortical excitability between stimulation conditions ( p = 0.90 ) . That the targeted delivery of anodal tDCS during task performance both increased TTF and the amount of muscle fatigue in a subset of subjects suggests that augmenting cortical excitability with tDCS enhanced descending drive to the spinal motorpool to recruit more motor units . The results also suggest that the application of tDCS during performance of fatiguing activity has the potential to bolster the capacity to exercise under conditions required to derive benefits due to overload The central nervous system seems to have an important role in fatigue and exercise tolerance . Novel noninvasive techniques of neuromodulation can provide insights on the relationship between brain function and exercise performance . The purpose of this study was to determine the effects of transcranial direct current stimulation ( tDCS ) on physical performance and physiological and perceptual variables with regard to fatigue and exercise tolerance . Eleven physically active subjects participated in an incremental test on a cycle simulator to define peak power output . During 3 visits , the subjects experienced 3 stimulation conditions ( anodal , cathodal , or sham tDCS — with an interval of at least 48 h between conditions ) in a r and omized , counterbalanced order to measure the effects of tDCS on time to exhaustion at 80 % of peak power . Stimulation was administered before each test over 13 min at a current intensity of 2.0 mA. In each session , the Brunel Mood State question naire was given twice : after stimulation and after the time-to-exhaustion test . Further , during the tests , the electromyographic activity of the vastus lateralis and rectus femoris muscles , perceived exertion , and heart rate were recorded . RM-ANOVA showed that the subjects performed better during anodal primary motor cortex stimulation ( 491 ± 100 s ) compared with cathodal stimulation ( 443 ± 11 s ) and sham ( 407 ± 69 s ) . No significant difference was observed between the cathodal and sham conditions . The effect sizes confirmed the greater effect of anodal M1 tDCS ( anodal x cathodal = 0.47 ; anodal x sham = 0.77 ; and cathodal x sham = 0.29 ) . Magnitude-based inference suggested the anodal condition to be positive versus the cathodal and sham conditions . There were no differences among the three stimulation conditions in RPE ( p = 0.07 ) or heart rate ( p = 0.73 ) . However , as hypothesized , RM- ANOVA revealed a main effect of time for the two variables ( RPE and HR : p < 0.001 ) . EMG activity also did not differ during the test accross the different conditions . We conclude that anodal tDCS  increases exercise tolerance in a cycling-based , constant-load exercise test , performed at 80 % of peak power . Performance was enhanced in the absence of changes in physiological and perceptual variables BACKGROUND Transcranial direct current stimulation ( tDCS ) has been used to enhance endurance performance but its precise mechanisms and effects remain unknown . OBJECTIVE To investigate the effect of bilateral tDCS on neuromuscular function and performance during a cycling time to task failure ( TTF ) test . METHODS Twelve participants in r and omized order received a placebo tDCS ( SHAM ) or real tDCS with two cathodes ( CATHODAL ) or two anodes ( ANODAL ) over bilateral motor cortices and the opposite electrode pair over the ipsilateral shoulders . Each session lasted 10 min and current was set at 2 mA. Neuromuscular assessment was performed before and after tDCS and was followed by a cycling time to task failure ( TTF ) test . Heart rate ( HR ) , ratings of perceived exertion ( RPE ) , leg muscle pain ( PAIN ) and blood lactate accumulation ( ΔB[La- ] ) in response to the cycling TTF test were measured . RESULTS Corticospinal excitability increased in the ANODAL condition ( P < 0.001 ) while none of the other neuromuscular parameters showed any change . Neuromuscular parameters did not change in the SHAM and CATHODAL conditions . TTF was significantly longer in the ANODAL ( P = 0.003 ) compared to CATHODAL and SHAM conditions ( 12.61 ± 4.65 min ; 10.61 ± 4.34 min ; 10.21 ± 3.47 min respectively ) , with significantly lower RPE and higher ΔB[La- ] ( P < 0.001 ) . No differences between conditions were found for HR ( P = 0.803 ) and PAIN during the cycling TTF test ( P = 0.305 ) . CONCLUSION Our findings demonstrate that tDCS with the anode over both motor cortices using a bilateral extracephalic reference improves endurance performance Transcranial direct current stimulation ( tDCS ) can increase cortical excitability of a targeted brain area , which may affect endurance exercise performance . However , optimal electrode placement for tDCS remains unclear . We tested the effect of two different tDCS electrode montages for improving exercise performance .  Nine subjects underwent a control ( CON ) , placebo ( SHAM ) and two different tDCS montage sessions  in a r and omized design . In one tDCS session , the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead ( HEAD ) , while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electrode above the shoulder ( SHOULDER ) . tDCS was delivered for 10min at 2.0mA , after which participants performed an isometric time to exhaustion ( TTE ) test of the right knee extensors . Peripheral and central neuromuscular parameters were assessed at baseline , after tDCS application and after TTE . Heart rate ( HR ) , ratings of perceived exertion ( RPE ) , and leg muscle exercise-induced muscle pain ( PAIN ) were monitored during the TTE . TTE was longer and RPE lower in the SHOULDER condition ( P<0.05 ) . Central and peripheral parameters , and HR and PAIN did not present any differences between conditions after tDCS stimulation ( P>0.05 ) . In all conditions maximal 
    Output:
    
Furthermore , the sub- analysis showed that anodal tDCS over M1 and stimulation duration s longer than 10 min produced the best results in terms of TTF performance enhancement .
Additionally , the effects of anodal tDCS were larger during full body exercises ( i.e. , cycling ) when compared to uniarticular tasks .
In conclusion , the current meta- analysis indicated that anodal tDCS leads to small and moderate effects on MVC and TTF , respectively