Transcranial Direct Current Stimulation Enhances Muscle Strength of Non-dominant Knee in Healthy Young Males

The acute effects of motor cortex transcranial direct current stimulation on athletic performance in healthy adults: A systematic review and meta-analysis

This systematic review and meta-analysis assesses independently the acute effects of anodal and cathodal motor cortex transcranial direct current stimulation (tDCS) on athletic performance in healthy adults. Besides, it evaluates the unique and conjoint effects of potential moderators (i.e., stimulation parameters, exercise type, subjects' training status and risk of bias). Online database search was performed from inception until March 18th 2024 (PROSPERO: CRD42023355461). Forty-three controlled trials were included in the systematic review, 40 in the anodal tDCS meta-analysis (68 effects), and 9 (11 effects) in the cathodal tDCS meta-analysis. Performance enhancement between pre- and post-stimulation was the main outcome measure considered. The anodal tDCS effects on physical performance were small to moderate (g = .29, 95%CI [.18, .40], PI = -.64 to 1.23, I2 = 64.0%). Exercise type, training status and use of commercial tDCS were significant moderators of the results. The cathodal tDCS effects were null (g = .04, 95%CI [-.05, .12], PI = -.14 to .23, I2 = 0%), with a small to moderate heterogeneity entirely due to sampling error, thus impairing further moderator analysis. These findings hold significant implications for the field of brain stimulation and physical performance, as they not only demonstrate a small to moderate effect of acute tDCS but also identify specific categories of individuals, devices and activities that are more susceptible to improvements. By addressing the multidimensional factors influencing the mechanisms of tDCS, we also provide suggestions for future research.

Acute Effect of Transcranial Direct Current Stimulation in Pelvic Floor Muscle Function in Young Healthy Women: Initial Findings of a Randomized Controlled Trial

INTRODUCTION AND HYPOTHESIS

Transcranial direct current stimulation (tDCS) can enhance muscle function in healthy individuals. However, it is unknown if tDCS associated with pelvic floor muscle training (PFMT) can improve pelvic floor muscle function (PFMF) in healthy women. The aim of this study was to investigate the acute effect of a single session of tDCS in PFMF compared with sham-tDCS in healthy women.

METHODS

A double-blind, cross-over, randomized clinical trial was conducted with healthy, nulliparous and sexually active women. PFMF was assessed by bidigital palpation (PERFECT scale) and intravaginal pressure by a manometer (Peritron™). Participants randomly underwent two tDCS sessions (active and sham) 7 days apart. The electrode was positioned equal for both protocols, the anode electrode in the supplementary motor area (M1) and the cathode electrode in the right supraorbital frontal cortex (Fp2). The current was applied for 20 min at 2 mA in active stimulation and for 30 s in sham-tDCS. The tDCS applications were associated with verbal instructions to PFMT in a seated position. After each tDCS session PFMF was reevaluated.

RESULTS

Twenty young healthy women (aged 23.4 ± 1.7 years; body mass index 21.7 ± 2.2 kg/m2) were included. No difference was observed in power, endurance, and intravaginal pressure of PFMF (p > 0.05). The number of sustained contractions improved from 3.0 (2.0-3.5) to 4.0 (3.0-5.0) after active-tDCS (p = 0.0004) and was superior to sham-tDCS (p = 0.01).

CONCLUSION

The number of sustained contractions of PFM improved immediately after a single active-tDCS session, with a difference compared with the post-intervention result of sham-tDCS in healthy young women.

Does a single session of transcranial direct current stimulation enhance both physical and psychological performance in national- or international-level athletes? A systematic review

Some studies showed that a single session of transcranial direct current stimulation (tDCS) has the potential of modulating motor performance in healthy and athletes. To our knowledge, previously published systematic reviews have neither comprehensively investigated the effects of tDCS on athletic performance in both physical and psychological parameters nor investigated the effects of tDCS on high-level athletes. We examined all available research testing a single session of tDCS on strength, endurance, sport-specific performance, emotional states and cognitive performance for better application in competition and pre-competition trainings of national- or international-level athletes. A systematic search was conducted in PubMed, Web of Science, EBSCO, Embase, and Scopus up until to June 2023. Studies were eligible when participants had sports experience at a minimum of state and national level competitions, underwent a single session of tDCS without additional interventions, and received either sham tDCS or no interventions in the control groups. A total of 20 experimental studies (224 participants) were included from 18 articles. The results showed that a single tDCS session improved both physical and psychological parameters in 12 out of the 18 studies. Of these, six refer to the application of tDCS on the motor system (motor cortex, premotor cortex, cerebellum), five on dorsolateral prefrontal cortex and two on temporal cortex. The most sensitive to tDCS are strength, endurance, and emotional states, improved in 67%, 75%, and 75% of studies, respectively. Less than half of the studies showed improvement in sport-specific tasks (40%) and cognitive performance (33%). We suggest that tDCS is an effective tool that can be applied to competition and pre-competition training to improve athletic performance in national- or international-level athletes. Further research would explore various parameters (type of sports, brain regions, stimulation protocol, athlete level, and test tasks) and neural mechanistic studies in improving efficacy of tDCS interventions. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022326989, identifier CRD42022326989.

The effect of warm-up with transcranial direct current stimulation on performance factors in collegiate golfers

PURPOSE

This study aimed to determine the effects of warm-up using transcranial direct current stimulation (tDCS) on performance factors in collegiate golfers and to provide a scientific basis for the effectiveness and methodology of tDCS. We sought to compare the effects of tDCS as an additional treatment during warm-up. tDCS is generally activated when a small electric current is applied to the motor cortex of the cerebral cortex, which has been reported to be helpful in improving motor function. Therefore, we sought to prove the effectiveness of combined warm-up exercise and tDCS.

METHODS

Twenty-two collegiate male golfers were divided into tDC- (tDCS; n=11) and sham-treated (sham; n=11) groups. To examine performance factors, the following were assessed following tDCS application: carry, clubhead speed (CHS), ball speed (BS) for driver performance, countermovement jump (CMJ) for lower extremity muscle power, global rating of change (GRC) for the subjective change in condition of the participants, and test of attentional interpersonal style (TAIS) for concentration.

RESULTS

This study showed that warm-up with tDCS had positive effects on carry (p=.004), CHS (p=.019), BS (p=.017) of driver performance, CMJ (p=.002), and GRC (p=.005), however, no significant effect on TAIS was found, which suggest that the effects of the warm-up with tDCS were significant for driver performances, CMJ, and GRC.

CONCLUSION

Future studies should independently validate the effectiveness of tDCS and apply it to different situations and timeframes, such as training and competitions, to provide new alternative strategies or performance improvement.

The impact of cerebellar transcranial direct current stimulation on isometric bench press performance in trained athletes

Athletic development centers on optimizing performance, including technical skills and fundamental motor abilities such as strength and speed. Parameters such as maximum contraction force and rate of force development, influence athletic success, although performance gains become harder to achieve as athletic abilities increase. Non-invasive transcranial direct current stimulation of the cerebellum (CB-tDCS) has been used successfully to increase force production in novices, although the potential effects in athletes remain unexplored. The present study examined the effects of CB-tDCS on maximum isometric voluntary contraction force (MVCiso) and isometric rate of force development (RFDiso) during a bench press task in well-trained athletes. 21 healthy, male, strength-trained athletes participated in a randomized, sham-controlled, double-blinded crossover design. Each participant completed the isometric bench press (iBP) task on two separate days, with at least 5 days between sessions, while receiving either CB-tDCS or sham stimulation. Electromyography (EMG) recordings of three muscles involved in iBP were acquired bilaterally to uncover differences in neuromuscular activation and agonist-antagonist co-contraction between conditions. Contrary to our hypothesis, no significant differences in MVCiso and RFDiso were observed between CB-tDCS and sham conditions. Furthermore, no tDCS-induced differences in neuromuscular activation or agonist-antagonist co-contraction were revealed. Here, we argue that the effects of CB-tDCS on force production appear to depend on the individual's training status. Future research should study individual differences in tDCS responses between athletes and novices, as well as the potential of high-definition tDCS for precise brain region targeting to potentially enhance motor performance in athletic populations.

Effects of anodic transcranial direct current stimulation combined with physical training on the performance of elite swimmers

Objective

Anodal transcranial direct current stimulation (a-tDCS) has been used to improve athletic performance in various populations; however, its role in improving performance in elite athletes is unclear. This study aimed to investigate the effects of a-tDCS on athletic performance in elite athletes.

Methods

We used a single-blind, randomized controlled experimental design and recruited 24 national-level freestyle swimmers from China. All athletes were randomly divided into two groups; the experimental group underwent a-tDCS (current 2 mA for 20 min) combined with physical training, and the control group underwent a-tDCS sham stimulation combined with physical training. The physical training program was identical in the experimental and control groups. The intervention period was 6 weeks, with five weekly sessions of 110 min each, consisting of 20 min of a-tDCS and 90 min of physical training. Base strength, explosive strength, aerobic endurance, and anaerobic endurance were measured in the athletes before and after the intervention.

Results

The results were as follows. 1) Basic strength: There was a significant improvement in 5RM pull-ups in the experimental and control groups before and after the intervention (p < 0.05). 2) Explosive strength: There was a significant improvement in vertical jump and swimming start distance into the water in the experimental and control groups before and after the intervention (p < 0.05). 3) Aerobic endurance: There was no significant improvement in the experimental and control groups before and after the intervention. 4) Anaerobic endurance: There was a significant improvement in 400 m running performance in the experimental and control groups before and after the intervention (p < 0.05).

Conclusion

Compared to physical training alone, a-tDCS combined with physical training can better improve the athletic performance of high-level swimmers, especially in basic strength, explosive strength, and aerobic endurance.

The effect of transcranial direct current stimulation on bilateral asymmetry and joint angles of the lower limb for females when crossing obstacles

BACKGROUND

Gait asymmetry is often accompanied by the bilateral asymmetry of the lower limbs. The transcranial direct current stimulation (tDCS) technique is widely used in different populations and scenarios as a potential tool to improve lower limb postural control. However, whether cerebral cortex bilateral tDCS has an interventional effect on postural control as well as bilateral symmetry when crossing obstacles in healthy female remains unknown.

METHODS

Twenty healthy females were recruited in this prospective study. Each participant walked and crossed a height-adjustable obstacle. Two-way repeated ANOVA was used to evaluate the effect of group (tDCS and sham-tDCS) and height (30%, 20%, and 10% leg length) on the spatiotemporal and maximum joint angle parameters for lower limb crossing obstacles. The Bonferroni post-hoc test and paired t-test were used to determine the significance of the interaction effect or main effect. The statistically significant differences were set at p < 0.05.

RESULTS

The Swing time (SW) gait asymmetry (GA), Stance time (ST) GA, leading limb hip-knee-ankle maximum joint angles and trailing limb hip-knee maximum joint angles decreased in the tDCS condition compared to the sham-tDCS condition at 30%, 20% leg's length crossing height except for 10% leg's length, whereas there was a significant decrease in SW/ST GA between the tDCS condition and the sham-tDCS condition at 30%, 20%, 10% leg's length crossing height (P < 0.05).

CONCLUSION

We conclude that tDCS intervention is effective to reduce bilateral asymmetry in spatio-temporal parameters and enhance dynamic balance in female participants during obstacle crossing when the heights of the obstacles were above 10% of the leg's length.

TRIAL REGISTRATION NO

ChiCTR2100053942 (date of registration on December 04, 2021). Prospectively registered in the Chinese Clinical Trial Registry.

Evaluation of Transcranial Direct Current Stimulation in Motor Function and Neural Rehabilitation

ABSTRACT

Transcranial direct current stimulation (tDCS) is used in neuromodulation to regulate the excitability of the cerebral cortex and induce neural plasticity. It was initially used to rehabilitate patients with neurological diseases. However, with the increasing number of studies involving healthy individuals, this technology is currently used in the field of sports as well. The administration of tDCS to the cerebral cortex, especially over the primary motor cortex (M1), has been found to improve muscle strength, enhance endurance, and promote motor skills in humans. This study mainly summarizes the effects of tDCS on motor function, mainly involving motor promotion of tDCS in healthy athletes and nonathletes, and in patients diagnosed with neurological diseases. The tDCS is a promising and effective tool used to promote motor function by regulating cortical excitability. However, no consensus is available regarding individually appropriate models of tDCS.

Effects of high-definition transcranial direct current stimulation on the cortical-muscular functional coupling and muscular activities of ankle dorsi-plantarflexion under running-induced fatigue

Transcranial direct current stimulation (tDCS) can improve motor control performance under fatigue. However, the influences of tDCS on factors contributing to motor control (e.g., cortical-muscular functional coupling, CMFC) are unclear. This double-blinded and randomized study examined the effects of high-definition tDCS (HD-tDCS) on muscular activities of dorsiflexors and plantarflexors and CMFC when performing ankle dorsi-plantarflexion under fatigue. Twenty-four male adults were randomly assigned to receive five sessions of 20-min HD-tDCS targeting primary motor cortex (M1) or sham stimulation. Three days before and 1 day after the intervention, participants completed ankle dorsi-plantarflexion under fatigue induced by prolonged running exercise. During the task, electroencephalography (EEG) of M1 (e.g., C1, Cz) and surface electromyography (sEMG) of several muscles (e.g., tibialis anterior [TA]) were recorded synchronously. The corticomuscular coherence (CMC), root mean square (RMS) of sEMG, blood lactate, and maximal voluntary isometric contraction (MVC) of ankle dorsiflexors and plantarflexors were obtained. Before stimulation, greater beta- and gamma-band CMC between M1 and TA were significantly associated with greater RMS of TA (r = 0.460-0.619, p = 0.001-0.024). The beta- and gamma-band CMC of C1-TA and Cz-TA, and RMS of TA and MVC torque of dorsiflexors were significantly higher after HD-tDCS than those at pre-intervention in the HD-tDCS group and post-intervention in the control group (p = 0.002-0.046). However, the HD-tDCS-induced changes in CMC and muscle activities were not significantly associated (r = 0.050-0.128, p = 0.693-0.878). HD-tDCS applied over M1 can enhance the muscular activities of ankle dorsiflexion under fatigue and related CMFC.

Effect of tDCS targeting the M1 or left DLPFC on physical performance, psychophysiological responses, and cognitive function in repeated all-out cycling: a randomized controlled trial

BACKGROUND

Despite reporting the positive effects of transcranial direct current stimulation (tDCS) on endurance performance, very few studies have investigated its efficacy in anaerobic short all-out activities. Moreover, there is still no consensus on which brain areas could provide the most favorable effects on different performance modalities. Accordingly, this study aimed to investigate the effects of anodal tDCS (a-tDCS) targeting the primary motor cortex (M1) or left dorsolateral prefrontal cortex (DLPFC) on physical performance, psychophysiological responses, and cognitive function in repeated all-out cycling.

METHODS

In this randomized, crossover, and double-blind study, 15 healthy physically active men underwent a-tDCS targeting M1 or the left DLPFC or sham tDCS in separate days before performing three bouts of all-out 30s cycling anaerobic test. a-tDCS was applied using 2 mA for 20 min. Peak power, mean power, fatigue index, and EMG of the quadriceps muscles were measured during each bout. Heart rate, perceived exertion, affective valence, and arousal were recorded two minutes after each bout. Color-word Stroop test and choice reaction time were measured at baseline and after the whole anaerobic test.

RESULTS

Neither tDCS montage significantly changed peak power, mean power, fatigue index, heart rate, affective valence, arousal, and choice reaction time (p> 0.05). a-tDCS over DLPFC significantly lowered RPE of the first bout (compared to sham; p=0.048, Δ=-12.5%) and third bout compared to the M1 (p=0.047, Δ=-12.38%) and sham (p=0.003, Δ=-10.5%), increased EMG of the Vastus Lateralis muscle during the second (p=0.016, Δ= +40.3%) and third bout (p=0.016, Δ= +42.1%) compared to sham, and improved the score of color-word Stroop test after the repeated all-out task (p=0.04, Δ= +147%). The qualitative affective response (valence and arousal) was also higher under the M1 and DLPFC compared to the sham.

CONCLUSION

We concluded that tDCS targeting M1 or DLPFC does not improve repeated anaerobic performance. However, the positive effect of DLPFC montage on RPE, EMG, qualitative affective responses, and cognitive function is promising and paves the path for future research using different tDCS montages to see any possible effects on anaerobic performance.

TRIAL REGISTRATION

This study was approved by the Ethics Committee of Razi University (IR.RAZI.REC.1400.023) and registered in the Iranian Registry of Clinical Trials (IRCT id: IRCT20210617051606N5; Registration Date: 04/02/2022).

The impact of bilateral anodal transcranial direct current stimulation of the premotor and cerebellar cortices on physiological and performance parameters of gymnastic athletes: a randomized, cross-over, sham-controlled study

Professional sports performance relies critically on the interaction between the brain and muscles during movement. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique which modulates cortical excitability and can be used to improve motor performance in athletes. The present study aimed to investigate the effect of bilateral anodal tDCS (2 mA, 20 min) over the premotor cortex or cerebellum on motor and physiological functions and peak performance of professional gymnastics athletes. Seventeen professional gymnastics athletes participated in a randomized, sham-controlled, crossover study. In this study, we assessed the efficacy of two anodal tDCS protocols (2 mA, 20 min) with stimulation over the bilateral premotor cortex or cerebellum with the return electrodes placed over the opposite supraorbital areas. Power speed, strength coordination, endurance, static and dynamic strength, static and dynamic flexibility, and rating of perceived exertion were measured before and immediately after tDCS interventions (bilateral anodal tDCS over premotor cortices, anodal tDCS over the cerebellum, and sham tDCS). Additionally, physiological muscle performance parameters, including maximum voluntary isometric contraction (MVIC) of upper body muscles, were assessed during tDCS. Bilateral anodal tDCS over the premotor cortex, compared to anodal tDCS over the cerebellum and sham tDCS conditions, significantly improved power speed, strength coordination, and static and dynamic strength variables of professional gymnastics athletes. Furthermore, bilateral anodal tDCS over the cerebellum, compared to sham tDCS, significantly improved strength coordination. Moreover, bilateral premotor anodal tDCS significantly increased MVIC of all upper body muscles during stimulation, while anodal tDCS over the cerebellum increased MVIC in only some muscles. Bilateral anodal tDCS over the premotor cortex, and to a minor degree over the cerebellum, might be suited to improve some aspects of motor and physiological functions and peak performance levels of professional gymnastics athletes.Clinical Trial Registration ID: IRCT20180724040579N2.

Anodal Transcranial Direct Current Stimulation over the Right Dorsolateral Prefrontal Cortex Boosts Decision Making and Functional Impulsivity in Female Sports Referees

We investigated the effect of anodal transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex (rDLPFC) on the sensitive decision making of female team sports referees. Twenty-four female referees voluntarily participated in this randomized, double-blind, crossover, and sham-controlled study. In three different sessions, participants received either anodal (a-tDCS; anode (+) over F4, cathode (-) over the supraorbital region (SO)), cathodal (c-tDCS; -F4/+SO), or sham tDCS (sh-tDCS) in a randomized and counterbalanced order. a-tDCS and c-tDCS were applied with 2 mA for 20 min. In sh-tDCS, the current was turned off after 30 s. Before and after tDCS, participants performed the computerized Iowa Gambling Task (IGT) and Go/No Go impulsivity (IMP) tests. Only a-tDCS improved IGT and IMP scores from pre to post. The delta (Δ = post-pre) analysis showed a significantly higher ΔIGT in a-tDCS compared to c-tDCS (p = 0.02). The ΔIMP was also significantly higher in a-tDCS compared to sh-tDCS (p = 0.01). Finally, the reaction time decreased significantly more in a-tDCS (p = 0.02) and sh-tDCS (p = 0.03) than in c-tDCS. The results suggest that the a-tDCS improved factors related to sensitive decision making in female team sports referees. a-tDCS might be used as an ergogenic aid to enhance decision performance in female team sports referees.

Anodal tDCS over the left DLPFC but not M1 increases muscle activity and improves psychophysiological responses, cognitive function, and endurance performance in normobaric hypoxia: a randomized controlled trial

BACKGROUND

Transcranial direct current stimulation (tDCS) has been shown to have positive effects on exercise performance and cognitive function in the normal ambient condition. Hypoxia is deemed a stressful situation with detrimental effects on physiological, psychological, cognitive, and perceptual responses of the body. Nevertheless, no study has evaluated the efficacy of tDCS for counteracting the negative effects of hypoxic conditions on exercise performance and cognition so far. Hence, in the present study, we investigated the effects of anodal tDCS on endurance performance, cognitive function, and perceptual responses in hypoxia.

PARTICIPANTS AND METHODS

Fourteen endurance-trained males participated in five experimental sessions. After familiarization and measuring peak power output in hypoxia, in the first and second sessions, through the 3rd to 5th sessions, participants performed a cycling endurance task until exhaustion after 30 min hypoxic exposure at resting position followed by 20 min of anodal stimulation of the motor cortex (M1), left dorsolateral prefrontal cortex (DLPFC), or sham-tDCS. Color-word Stroop test and choice reaction time were measured at baseline and after exhaustion. Time to exhaustion, heart rate, saturated O₂, EMG amplitude of the vastus lateralis, vastus medialis, and rectus femoris muscles, RPE, affective response, and felt arousal were also measured during the task under hypoxia.

RESULTS

The results showed a longer time to exhaustion (+ 30.96%, p₌0.036), lower RPE (- 10.23%, p ₌ 0.045) and higher EMG amplitude of the vastus medialis muscle (+ 37.24%, p₌0.003), affective response (+ 260%, p₌0.035) and felt arousal (+ 28.9%, p₌0.029) in the DLPFC tDCS compared to sham. The choice reaction time was shorter in DLPFC tDCS compared to sham (- 17.55%, p₌0.029), and no differences were seen in the color-word Stroop test among the conditions under hypoxia. M1 tDCS resulted in no significant effect for any outcome measure.

CONCLUSIONS

We concluded that, as a novel finding, anodal stimulation of the left DLPFC might provide an ergogenic aid for endurance performance and cognitive function under the hypoxic condition probably via increasing neural drive to the working muscles, lowering RPE, and increasing perceptual responses.

Effects of Bilateral Extracephalic Transcranial Direct Current Stimulation on Lower Limb Kinetics in Countermovement Jumps

OBJECTIVE

Transcranial direct current stimulation (tDCS) is an effective method for improving sports/exercise performance in humans. However, studies examining the effects of tDCS on jumping performance have reported inconsistent findings, and there is a paucity of studies investigating the effects of tDCS on lower limb energy and kinetics in countermovement jumps (CMJs). Thus, we investigated the effects of tDCS on countermovement jump (CMJ) performance and analysed kinetic variations in the ankle, knee, and hip joints.

METHODS

In total, 15 healthy young participants randomly received anodal or sham bilateral stimulation of the primary motor cortex (M1). The bilateral tDCS (Bi-tDCS) montage used an intensity of 2 mA for a 20 min monophasic continuous current. Jump height, energy, and lower limb kinetic data in CMJs were collected at pre-stimulation (Pre), post-0 min (Post-0), and post-30 min (Post-30) using a motion capture system and two 3D force plates. Jump height, lower extremity energy, and kinetic variables in CMJs were analysed with two-way repeated-measures ANOVA.

RESULTS

(1) Compared to the baseline and sham conditions, the jump height increased except that at Post-30 relative to the sham condition, and the total net energy of lower limbs increased at Post-30 relative to the baseline. (2) Compared to the baseline, the ankle positive energy and net energy decreased in the sham condition; Compared to the baseline and values at Post-0, the maximum ankle torque at Post-30 decreased in both stimulation conditions. (3) The maximum knee power increased compared to the baseline and sham conditions. (4) Regardless of time points, the maximum hip torque in the tDCS condition was higher than it was in the sham condition.

CONCLUSION

Bi-tDCS is an effective method for improving jump height by modulating ankle and knee net energy. The net energy improvement of the lower extremities may be due to variation in the kinetic chain resulting from tDCS-enhanced knee exploration force and maximum hip strength in CMJs. The effects of Bi-tDCS gradually decrease.

A dual-mode neurostimulation approach to enhance athletic performance outcome in experienced taekwondo practitioners

Transcranial Direct Current Stimulation (tDCS) is a growing empirical approach to improve athletic performance. Some recent studies have investigated the effects of transcutaneous spinal direct current stimulation (tsDCS) on the motor performance such as reaction time. TDCS and tsDCS can lead to alteration of the spontaneous neural activity, and the membrane potentials of motor neurons in cerebral cortex and spinal interneurons, respectively. Given the paucity of experimental studies on the non-invasive brain stimulation in the field of sports neuroscience, especially martial sports, the present study aimed at investigating the effects of neurostimulation in potentiating the motor and cognitive functions in experienced taekwondo practitioners. The study sample included 15 experienced male taekwondo players who received real or sham direct current stimulation on the primary motor cortex (M1) and the lumbar spinal segment (T12-L2) over two sessions, 72 h apart. Next, the performance of the participants was evaluated through a simulation of taekwondo exercise directly after the sham and real sessions. Moreover, a cognitive platform (CBS: Cambridge Brain Science) was used to investigate the participants' cognitive profile in each instance. Unlike sham stimulation, real tDCS was associated with improved selective attention and reaction time in both in the simulated task performance and cognitive examination. The concurrent cortical and trans-spinal tDCS was found to improve selective attention (31% performance improvement) (P < 0.0001) [EFFECT SIZE; 1.84]. and reduce reaction time (4.7% performance improvement) (P < 0.0001) [EFFECT SIZE; 0.02]. Meanwhile, the intervention failed to leave a significant change in cognitive functions evaluated through CBS (P > 0.05). As informed by our results, the present dual-mode neurostimulation could improve motor functions potentially through the effect of tsDCS over the spinal interneurons and tDCS over the primary motor cortex. Likewise, our findings suggested an improved performance in simulated taekwondo task after real- but not sham-stimulation. This study paves the way for designing neurostimulation protocols to improve the performance of professional athletes, namely martial art practitioners, including their accuracy and velocity of reactions. Such positive effects of neuostimulation in athletic performance as demonstrated in this research and similar reports are expected to enhance the athletes' success in professional competitions.

Transcranial direct current stimulation influences repetitive bimanual force control and interlimb force coordination

This study aimed to investigate the potential effect of bilateral transcranial direct current stimulation (tDCS) on repetitive bimanual force control and force coordination in healthy young adults. In this sham-controlled crossover study, 18 right-handed young adults were enrolled. Repetitive bimanual handgrip force control trials were performed by the participants at 40% of maximum voluntary contraction until task failure. We randomly provided bilateral active and sham tDCS to the primary motor cortex (M1) of each participant before conducting the repetitive bimanual force control task. We quantified the number of successful trials to assess the ability to maintain bimanual force control across multiple trials. Moreover, we estimated bimanual force control and force coordination by quantifying force accuracy, variability, regularity, and correlation coefficient in maximal and adjusted successful trials. Force asymmetry was calculated to examine potential changes in motor dependency on each hand during the task. Bilateral tDCS significantly increased the number of successful trials compared with sham tDCS. The adjusted successful trial revealed that participants who received bilateral tDCS maintained better bimanual force control and coordination, as indicated by decreased force variability and regularity as well as more negative correlation coefficient values in comparison with sham condition. Moreover, participants who received bilateral tDCS produced more force from the dominant hand than from the nondominant hand in both maximal and adjusted successful trials. These findings suggest that bilateral tDCS on M1 successfully maintains bimanual force control with better force coordination by modulating motor dependency.

Effects of Transcranial Direct Current Stimulation over the Primary Motor Cortex in Improving Postural Stability in Healthy Young Adults

Transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) is of increasing interest to improve motor performance in healthy adults and patients with respective deficits. This study aimed to examine whether tDCS over M1 can improve static and dynamic postural stability in young healthy adults. Seventeen healthy participants (mean age = 25.14 ± 2.50 (standard deviation, SD) years) received sham and anodal tDCS (2 mA) over the vertex at the Cz electrode position for 15 min. Static and dynamic postural stability were evaluated before and immediately after tDCS. The center of pressure (COP) sway area (COPSA) and COP maximum displacements to medio-lateral (COPML) and antero-posterior directions (COPAP) were used to evaluate static postural stability. The anterior−posterior stability index (APSI), medial−lateral stability index (MLSI), vertical stability index (VSI), dynamic postural stability index (DPSI), and time to stabilization (TTS) in forward (FL), 45° anterior lateral (LL), and 45° anterior medial (ML) direction landing, as well as the Y-balance composite score (YBTCS) were used to assess dynamic postural stability. The results showed that the LL-TTS (p = 0.044), non-dominant leg COPSA (p = 0.015), and YBTCS (p < 0.0001) were significantly improved in the real stimulation as compared with the sham stimulation session, and anodal tDCS significantly changed dominant leg COPAP (p = 0.021), FL-APSI (p < 0.0001), FL-TTS (p = 0.008), ML-TTS (p = 0.002), non-dominant leg YBTCS (p < 0.0001), and dominant leg YBTCS (p = 0.014). There were no significant differences in all obtained balance values in the sham stimulation session, except for non-dominant leg YBTCS (p = 0.049). We conclude that anodal tDCS over M1 has an immediate improving effect on static postural stability and dynamic performance in young healthy adults. This makes tDCS a promising adjuvant rehabilitation treatment to enhance postural stability deficits in the future.

Effects of Preceding Transcranial Direct Current Stimulation on Movement Velocity and EMG Signal during the Back Squat Exercise

This study aimed to evaluate the effects of preceding anodal transcranial direct stimulation (a-tDCS) over the dorsolateral prefrontal cortex (DLPFC) during the back squat exercise on movement velocity and surface electromyographic (sEMG) activity. Thirteen healthy, well-trained, male firefighters (34.72 ± 3.33 years; 178 ± 7.61 cm; 76.85 ± 11.21 kg; 26.8 ± 4.2 kg·m−2; back squat 1-repetition maximum 141.5 ± 16.3 kg) completed this randomised double-blinded sham-controlled crossover study. After familiarisation and basal measurements, participants attended the laboratory on two occasions separated by 72 h to receive either Sham or a-tDCS (current intensity of 2 mA for 20 min). Immediately after stimulation, participants completed three sets of 12 repetitions (70% of 1-RM) with three minutes of recovery between sets monitored with a linear position transducer. The sEMG of the rectus femoris (RF) and vastus lateralis (VL) of both legs were recorded. No significant differences were observed between a-tDCS and Sham interventions on mean concentric velocity at any set (p > 0.05). Velocity loss and effort index were significantly higher (p < 0.05) in set 3 compared to set 1 only in the a-tDCS group. The right-leg RM and right-leg VL elicited the greatest muscle activation during set 1 after a-tDCS and Sham, respectively (p < 0.05). Our results revealed that a-tDCS over the DLPFC might impact movement velocity or fatigue tolerance in well-trained individuals. Notwithstanding, significant differences in dominant-leg muscle activity were found both in a-tDCS and Sham.