Effects of Transcranial Direct Current Stimulation With Caffeine Intake on Muscular Strength and Perceived Exertion

Abstract

Lattari, E, Vieira, LAF, Oliveira, BRR, Unal, G, Bikson, M, de Mello Pedreiro, RC, Marques Neto, SR, Machado, S, and Maranhão-Neto, GA. Effects of transcranial direct current stimulation with caffeine intake on muscular strength and perceived exertion. J Strength Cond Res 33(5): 1237–1243, 2019—The aim of this study was to investigate the acute effects of transcranial direct current stimulation (tDCS) associated with caffeine intake on muscular strength and ratings of perceived exertion (RPE). Fifteen healthy young males recreationally trained (age: 25.3 ± 3.2 years, body mass: 78.0 ± 6.9 kg, height: 174.1 ± 6.1 cm) were recruited. The experimental conditions started with the administration of caffeine (Caff) or placebo (Pla) 1 hour before starting the anodal tDCS (a-tDCS or sham). There was an intake of 5 mg·kg−1 of Caff or 5 mg·kg−1 of Pla. After the intake, a-tDCS or sham was applied in the left dorsolateral prefrontal cortex with intensity of 2 mA and 20 minutes of duration. The experimental conditions were defined as Sham + Pla, a-tDCS + Pla, Sham + Caff, and a-tDCS + Caff. After the conditions, muscular strength and RPE were verified. Muscular strength was determined by volume load performed in bench press exercise. Muscular strength in Sham + Pla condition was lower compared with all others conditions (p < 0.05). The RPE in the Sham + Pla was greater compared with a-tDCS + Caff (p < 0.05). Muscular strength was greater in all experimental conditions, and a-tDCS + Caff had lower RPE compared with placebo. When very little gains in muscle strength are expected, both caffeine and tDCS were effective in increasing muscle strength. Besides, the improvement in RPE of the caffeine associated with a-tDCS could prove advantageous in participants experienced in strength training. In fact, coaches and applied sport scientists quantitating the intensity of training based on RPE.

Effects of Caffeine on Resistance Exercise: A Review of Recent Research

“…Over 20 new studies explored the effects of caffeine on different muscular endurance outcomes [6,8,9,11,16,21,22,26,29,30,35,36,38,41,44,45,48,49,[52][53][54][55]]. An ergogenic effect of caffeine on muscular endurance was observed in the majority of these studies, with the effect sizes ranging from small to large (Cohen's d: 0.18-2.21).…”

Acute Effects of Anodal Transcranial Direct Current Stimulation in Resistance and Power Exercises: A Brief Review for Coaches and Practitioners

“…Eleven reviews were identified and excluded, and 90 studies were screened for titles and abstracts. Then, 77 studies were excluded, and 13 were screened for full-texts, resulting in 6 studies for inclusion (3,35,43,46,47,59). The authors included 7 studies manually (13,26,42,58,73), 6 were found in the reference list of the studies, and 2 (19,44) were suggested to be included by the author (E.L.), considering that these studies were not found in the search or the references' lists.…”

Effects of Anodal Transcranial Direct Current Stimulation on Training Volume and Pleasure Responses in the Back Squat Exercise Following a Bench Press

“…Transcranial direct current stimulation consists of a noninvasive neuromodulatory technique that depolarizes (anodal stimulus) or hyperpolarizes (cathodal stimulus) the neuronal membrane (23). Also, when anodal tDCS (a-tDCS) is applied over the left DLPFC, there is evidence of an increased number of repetitions and a reduction in rating of perceived exertion (RPE) in both upper- (18) and lower-body (17) exercises, when compared with a sham stimulus (i.e., inactive form of stimulation used to control for the placebo effect). Given the relationship between the PFC and pleasure responses (27), there is indirect evidence suggesting that the improvements in volume obtained through the use of a-tDCS could be associated with psychological changes (i.e., perceived exertion and pleasure) (17,18).…”

“…Also, when anodal tDCS (a-tDCS) is applied over the left DLPFC, there is evidence of an increased number of repetitions and a reduction in rating of perceived exertion (RPE) in both upper- (18) and lower-body (17) exercises, when compared with a sham stimulus (i.e., inactive form of stimulation used to control for the placebo effect). Given the relationship between the PFC and pleasure responses (27), there is indirect evidence suggesting that the improvements in volume obtained through the use of a-tDCS could be associated with psychological changes (i.e., perceived exertion and pleasure) (17,18). However, this effect of a-tDCS applied over the left DLPFC on pleasure has not been assessed in RT yet, especially when a lower-body exercise is performed following an upper-body exercise.…”