Motor cortex tDCS does not improve strength performance in healthy subjects

Abstract

The influence of transcranial direct current stimulation (tDCS) upon maximal strength performance in exercises recruiting large muscle mass has not been established in healthy populations. The purpose of this study was to investigate whether anodal tDCS was able to increase the performance during maximal strength exercise (MSEX) in healthy subjects. Fourteen volunteers (age: 26 ± 4 yrs) performed two MSEX after anodal or sham tDCS (2mA; 20min prior MSEX), involving knee extensors and flexors in concentric isokinetic muscle actions of the dominant limb (3 sets of 10 repetitions). The electrical muscle activity (sEMG) of four recruited muscles was recorded during MSEX. Anodal tDCS was not able to improve force production (i.e., total work and peak torque), fatigue resistance, or electromyographic activity during MSEX when compared to sham condition. In conclusion, anodal tDCS applied upon the contralateral motor cortex was not capable of increasing the strength performance of knee extensors and flexors in young healthy subjects.Resumo-"ETCC sobre o córtex motor não aumenta o desempenho de força em sujeitos saudáveis." A influência da estimulação transcraniana por corrente contínua (ETCC) sobre o desempenho da força muscular em exercícios que recrutam grandes massas musculares ainda não foi estabelecido em populações saudáveis. O objetivo desse estudo foi investigar se a ETCC anódica seria capaz de aumentar o desempenho durante exercício máximo de força (EMF) em sujeitos saudáveis. Catorze voluntários (idade: 26 ± 4 anos) executaram dois EMF com aplicação prévia da ETCC anódica ou placebo (2mA; 20 mim), envolvendo músculos flexores e extensores do joelho dominante em ação concêntrica isocinética (3 séries de 10 repetições). A atividade elétrica muscular (sEMG) de quatro músculos recrutados foi registrada durante o EMF. A ETCC anódica não foi capaz de melhorar a produção de força (trabalho total e pico de torque), resistência à fadiga ou atividade eletromiográfica durante o EMF, quando comparada à condição placebo. Em conclusão, a ETCC anódica aplicada sobre o córtex motor contralateral não foi capaz de aumentar o desempenho de força de flexores e extensores de joelho em jovens saudáveis. Palavras-chave: neurociência, ETCC, neuromodulação, fadiga e reabilitação motoraResumen-"tDCS en motor corteza no aumenta el rendimiento de fuerza en sujetos sanos." La influencia de estimulación transcraneal de corriente directa (tDCS) en ejercicios de fuerza muscular de rendimiento que reclutan grandes masas musculares no se ha establecido en la población sana. El objetivo de este estudio fue investigar si la ETCC anódica podría mejorar el rendimiento durante el ejercicio máximo de la fuerza (EMF) en sujetos sanos. Catorce voluntarios (26 ± 4 años de edad) realizaron dos EMF con la aplicación previa de ETCC anódica y placebo (2 mA, 20 i) la participación de los flexores y extensores de la rodilla dominante en acción concéntrica (3 series de 10 repeticiones). La actividad eléctrica muscular (sEMG) en cuatro músculos reclutados se r...

Transcranial Direct Current Stimulation Does Not Affect Lower Extremity Muscle Strength Training in Healthy Individuals: A Triple-Blind, Sham-Controlled Study

“…In contract, among other tDCS studies, this first triple-blind study provides cogent evidence that the enhancement of knee torque was not seen with anodal tDCS combined with muscle strength training during each training session, compared to the sham tDCS with muscle strength training (Figure 4). However, the acute effects are inconsistent across studies (Tanaka et al, 2009, 2011; Montenegro et al, 2015, 2016; Angius et al, 2016; Washabaugh et al, 2016) and seem dependent on tDCS protocols, training tasks, muscle groups, and subject populations. In this context, computational modeling would be useful to understand the different spatial distributions of the electric field induced by different tDCS protocols (electrode configuration, size, or current intensity; Laakso et al, 2015, 2016).…”

“…The application of anodal tDCS to the primary motor cortex of the lower extremity transiently increases corticospinal excitability in healthy individuals (Jeffery et al, 2007; Tatemoto et al, 2013) and improves motor function in healthy individuals and patients with stroke (Tanaka et al, 2009, 2011; Madhavan et al, 2011; Sriraman et al, 2014; Chang et al, 2015; Montenegro et al, 2015, 2016; Angius et al, 2016; Washabaugh et al, 2016). Thus, anodal tDCS has a potential to become a new adjunct therapeutic strategy for the rehabilitation of leg motor function and locomotion following a stroke.…”

“…Several studies have examined the effect of a single session of tDCS on lower leg muscle strength, although the evidence is inconsistent (Tanaka et al, 2009, 2011; Montenegro et al, 2015, 2016; Angius et al, 2016; Washabaugh et al, 2016). Its effects seem dependent on tDCS protocols, training tasks, muscle groups, and subject populations.…”

Effect of transcranial direct current stimulation on exercise performance: A systematic review and meta-analysis

“…Regarding isokinetic muscle strength performance, the available studies stimulated different brain regions and found opposing results. Sales et al [64] found improved isokinetic muscle strength of the knee extensors after a-tDCS applied to the left TC, while Montenegro et al [63] found no difference after a-tDCS applied to M1.…”

The Tolerability and Efficacy of 4 mA Transcranial Direct Current Stimulation on Leg Muscle Fatigability

“…Strength and fatigue testing were performed on an isokinetic dynamometer (HUMAC NORM, CSMi, Stoughton, MA, USA). The strength test started with a 15 repetition submaximal warm-up of the knee extensors and flexors (concentric/concentric, 60 • /s), followed by five sets of one maximal effort knee extension and flexion (concentric/concentric, 60 • /s [37]), with ≥30 s rest between sets. The largest torque was retained for dominance verification (i.e., right stronger than left).…”