Acute effect of high-definition and conventional tDCS on exercise performance and psychophysiological responses in endurance athletes: a randomized controlled trial

Abstract

Transcranial direct current stimulation (tDCS) has been used aiming to boost exercise performance and inconsistent findings have been reported. One possible explanation is related to the limitations of the so-called “conventional” tDCS, which uses large rectangular electrodes, resulting in a diffuse electric field. A new tDCS technique called high-definition tDCS (HD-tDCS) has been recently developed. HD-tDCS uses small ring electrodes and produces improved focality and greater magnitude of its aftereffects. This study tested whether HD-tDCS would improve exercise performance to a greater extent than conventional tDCS. Twelve endurance athletes (29.4 ± 7.3 years; 60.15 ± 5.09 ml kg−1 min−1) were enrolled in this single-center, randomized, crossover, and sham-controlled trial. To test reliability, participants performed two time to exhaustion (TTE) tests (control conditions) on a cycle simulator with 80% of peak power until volitional exhaustion. Next, they randomly received HD-tDCS (2.4 mA), conventional (2.0 mA), or active sham tDCS (2.0 mA) over the motor cortex for 20-min before performing the TTE test. TTE, heart rate (HR), associative thoughts, peripheral (lower limbs), and whole-body ratings of perceived exertion (RPE) were recorded every minute. Outcome measures were reliable. There was no difference in TTE between HD-tDCS (853.1 ± 288.6 s), simulated conventional (827.8 ± 278.7 s), sham (794.3 ± 271.2 s), or control conditions (TTE1 = 751.1 ± 261.6 s or TTE2 = 770.8 ± 250.6 s) [F(1.95; 21.4) = 1.537; P = 0.24; η2p = 0.123]. There was no effect on peripheral or whole-body RPE and associative thoughts (P > 0.05). No serious adverse effect was reported. A single session of neither HD-tDCS nor conventional tDCS changed exercise performance and psychophysiological responses in athletes, suggesting that a ceiling effect may exist.

Case Report: Initial Evidence of Safety and Efficacy of High Definition-Transcranial Direct Current Stimulation in a Patient With Neuropathic Pain and Implanted Spinal Cord Stimulator

“…This may be in line with the observation that a-tDCS over M1 may have a superior therapeutic effect on the lower limbs relative to face and hand areas ( 10 ). Thus, the effect of tDCS in other brain areas, such as the DLPFC or S1, may provide different results ( 35 , 36 ) since M1 had no significant relationship with the NWC-T and PRI-T subscales of MPQ-DLV. In addition, various factors (e.g., anatomical and functional network variations, psychological and neurophysiological states, receptor sensibility and neurotransmitter levels, etc.)…”

“…In addition, various factors (e.g., anatomical and functional network variations, psychological and neurophysiological states, receptor sensibility and neurotransmitter levels, etc.) could affect how one responds to tDCS ( 36 ).…”

“…The duration of stimulation was prolonged on day 4 from 20 to 30 min. The configuration of the more novel and focal method of HD-tDCS with greater magnitude of its aftereffects ( 36 ) was the preferred treatment in our patient due to two of its advantages: its beneficial clinical effects with larger effect sizes is not only more comparable to invasive interventions such as epidural M1 stimulation for chronic pain ( 7 ) but it may also reduce potential side effects due to decreased stimulation of neighboring regions, making it a safer method ( 8 ).…”

Effects of Transcranial Direct Current Stimulation on Upper Limb Muscle Strength and Endurance in Healthy Individuals: A Systematic Review and Meta-Analysis

“…For example, Oki et al (2016) found that the improvement in endurance level after the a-tDCS intervention was negatively correlated with the baseline maximum strength level, indicating that the smaller the baseline maximum strength, the stronger the effect of tDCS intervention. We also consider that the use of tDCS in improving endurance still exhibits a “ceiling” effect, da Silva Machado et al (2021) reported that endurance athletes after two bicycle fatigue tasks used traditional tDCS and HD-tDCS intervention for 20 min, with an exercise intensity of 80% peak power and a stimulus intensity of approximately 2 mA. The results did not find that the TTE significantly improved, indicating that the use of tDCS in improving the baseline level of the subjects’ endurance may not be significant.…”

The Concept, Development, and Application of a Home-Based High-Definition tDCS for Bilateral Motor Cortex Modulation in Migraine and Pain

“…With HD electrodes arranged in arrays, researchers have greater flexibility to modulate excitability than in conventional tDCS ( 72 ). This unilateral focal M1 tDCS can precisely target the homuncular M1 face and head area ( 17 , 73 ), hand area ( 74 ), and lower limbs ( 75 ) based on pathological brain state and study purposes. In this way, researchers can optimize the effect with flexible use of HD electrodes (smaller than conventional, <5 cm 2 ), which overcomes the low spatial resolution of conventional tDCS ( 14 , 16 , 73 , 76 ).…”