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Transcranial Direct Current Stimulation (tDCS) is a non-invasive technique used to modulate neural tissue. Neuromodulation apparently improves cognitive functions in several neurologic diseases treatment and sports performance. In this study, we present a comprehensive, integrative review of tDCS for motor rehabilitation and motor learning in healthy individuals, athletes and multiple neurologic and neuropsychiatric conditions. We also report on neuromodulation mechanisms, main applications, current knowledge including areas such as language, embodied cognition, functional and social aspects, and future directions. We present the use and perspectives of new developments in tDCS technology, namely high-definition tDCS (HD-tDCS) which promises to overcome one of the main tDCS limitation (i.e., low focality) and its application for neurological disease, pain relief, and motor learning/rehabilitation. Finally, we provided information regarding the Transcutaneous Spinal Direct Current Stimulation (tsDCS) in clinical applications, Cerebellar tDCS (ctDCS) and its influence on motor learning, and TMS combined with electroencephalography (EEG) as a tool to evaluate tDCS effects on brain function.

In order to examine whether environmental settings influence psychological and physiological responses of women with obesity during self-paced walking, 38 women performed two exercise sessions (treadmill and outdoors) for 30 min, where oxygen uptake, heart rate, ratings of perceived exertion, affect, attentional focus, enjoyment, and future intentions to walk were analyzed. Physiological responses were similar during both sessions. However, during outdoor exercise, participants displayed higher externally focused attention, positive affect, and lower ratings of perceived exertion, followed by greater enjoyment and future intention to participate in outdoor walking. The more externally focused attention predicted greater future intentions to participate in walking. Therefore, women with obesity self-selected an appropriate exercise intensity to improve fitness and health in both environmental settings. Also, self-paced outdoor walking presented improved psychological responses. Health care professionals should consider promoting outdoor forms of exercise to maximize psychological benefits and promote long-term adherence to a physically active lifestyle.

Background: Novel coronavirus disease (COVID-19) morbidity is not restricted to the respiratory system, but also affects the nervous system. Non-invasive neuromodulation may be useful in the treatment of the disorders associated with COVID-19.Objective: To describe the rationale and empirical basis of the use of non-invasive neuromodulation in the management of patients with COVID-10 and related disorders.Methods: We summarize COVID-19 pathophysiology with emphasis of direct neuroinvasiveness, neuroimmune response and inflammation, autonomic balance and neurological, musculoskeletal and neuropsychiatric sequela. This supports the development of a framework for advancing applications of non-invasive neuromodulation in the management COVID-19 and related disorders.Results: Non-invasive neuromodulation may manage disorders associated with COVID-19 through four pathways: (1) Direct infection mitigation through the stimulation of regions involved in the regulation of systemic anti-inflammatory responses and/or autonomic responses and prevention of neuroinflammation and recovery of respiration; (2) Amelioration of COVID-19 symptoms of musculoskeletal pain and systemic fatigue; (3) Augmenting cognitive and physical rehabilitation following critical illness; and (4) Treating outbreak-related mental distress including neurological and psychiatric disorders exacerbated by surrounding psychosocial stressors related to COVID-19. The selection of the appropriate techniques will depend on the identified target treatment pathway.Conclusion: COVID-19 infection results in a myriad of acute and chronic symptoms, both directly associated with respiratory distress (e.g., rehabilitation) or of yet-to-be-determined etiology (e.g., fatigue). Non-invasive neuromodulation is a toolbox of techniques that based on targeted pathways and empirical evidence (largely in non-COVID-19 patients) can be investigated in the management of patients with COVID-19.

This study aimed to analyze the acute effect of anodal transcranial direct current stimulation (a-tDCS) over the primary motor cortex (M1) on the volume, perceived exertion, and neuromuscular performance measurements in trained and untrained adults. Twenty-four male adults (12 trained and 12 untrained) participated in this single-blind, randomized, and sham-controlled study. The participants performed three back squat repetitions using the 15RM load with maximal concentric velocity to assess neuromuscular performance before tDCS and 30-min after resistance exercise. Next, they were randomly assigned to a-tDCS over M1 or the sham condition. Participants performed ten sets of parallel back squat with 15RM load and repetitions sustained to momentary muscular failure. The total number of repetitions was higher (p<0.05) and perceived exertion was lower (p<0.05) after a-tDCS in both groups. Peak power, velocity, and force decreased in both groups after the RE session (p<0.05), but with a higher rate in untrained individuals (p<0.05). No significant effect was found for peak power, peak velocity, and peak force (p>0.05). This study suggests that using a-tDCS may improve the total volume of repetitions and perceived exertion in trained and untrained individuals.

BackgroundPleasure is a key factor for physical activity behavior in sedentary individuals. Inhibitory cognitive control may play an important role in pleasure perception while exercising, especially at high intensities. In addition, separate work suggests that autonomic regulation and cerebral hemodynamics influence the affective and cognitive responses during exercise.PurposeWe investigated the effects of exercise intensity on affect, inhibitory control, cardiac autonomic function, and prefrontal cortex (PFC) oxygenation.MethodsThirty-seven sedentary young adults performed two experimental conditions (exercise and control) in separate sessions in a repeated-measures design. In the exercise condition, participants performed a maximum graded exercise test on a cycle ergometer as we continuously measured oxygen consumption, heart rate variability (HRV), and PFC oxygenation. At each of 8 intensity levels we also measured inhibitory control (Stroop test), associative and dissociative thoughts (ADT), and affective/pleasure ratings. In the control condition, participants sat motionless on a cycle ergometer without active pedaling, and we collected the same measures at the same points in time as the exercise condition. We evaluated the main effects and interactions of exercise condition and intensity level for each measure using two-way repeated measures ANOVAs. Additionally, we evaluated the relationship between affect and inhibitory control, ADT, HRV, and PFC oxygenation using Pearson’s correlation coefficients.ResultsFor exercise intensities below and at the ventilatory threshold (VT), participants reported feeling neutral, with preservation of inhibitory control, while intensities above the VT were associated with displeasure (p<0.001), decreased inhibitory control and HRV (p<0.001), and increased PFC oxygenation (p<0.001). At the highest exercise intensity, pleasure was correlated with the low-frequency index of HRV (r = -0.34; p<0.05) and the low-frequency/high-frequency HRV ratio (r = -0.33; p<0.05). PFC deoxyhemoglobin was correlated with pleasure two stages above the VT (r = -0.37; p<0.05).ConclusionOur results support the notion that exercise at high intensities influences inhibitory control and one’s perception of pleasure, which are linked to changes in cardiac autonomic control and cerebral hemodynamics. These findings strengthen the existence of an integrated brain-heart-body system and highlight the importance of exercise intensity in exercise-related behavior in sedentary individuals.

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.