The aim of this study was investigate the effects of transcranial direct current stimulation (tDCS) on volume-load and ratings of perceived exertion. Fifteen young healthy individuals, aged between 20 and 30 years in advanced strength training were recruited. Test and retest of the 10 maximum repetitions (10RM) were performed to determine the reliability of load utilized. Subjects performed three experimental conditions in a randomized, double-blinded crossover design: anodic stimulation (a-tDCS), cathodic stimulation (c-tDCS) and sham (2 mA for 20 minutes targeting the dorsolateral prefrontal cortex cortex left). Immediately after the experimental conditions, subjects completed one set of maximum repetitions with 10RM load (volume-load) and answered to OMNI-RES (Post-stimulation) (level of significance p ≤ 0.05). The volume-load showed main effect for condition (F(2, 28)= 164.801; p<0.001). In post-stimulation, a-tDCS was greater than c-tDCS (p ≤ 0.001), and sham (p ≤ 0.001). For ratings of perceived exertion (OMNI-RES), the results showed main effect for condition (F(2, 28)=9.768; p ≤ 0.05). In post-stimulation, c-tDCS was greater than a-tDCS (p ≤ 0.05), and sham (p ≤ 0.05). We conclude that the use of a-tDCS may promote increased in volume-load for the LP45 exercise. Moreover, higher-volume loads are necessary to maximize muscle strength and anabolism.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique increasingly explored for Parkinson's disease (PD). Although evidence is still inconsistent, there are preliminary findings suggesting its efficacy to improve motor function in individuals with PD, as the role of secondary motor areas remains unclear. The goal of this study was to investigate the effects of left dorsolateral prefrontal cortex (DLPFC) tDCS on balance and functional mobility of individuals with PD. Seventeen individuals with PD, on-medication, aged between 40 and 90 years were recruited to enroll in a double-blind, randomized, cross-over trial. Each participant completed two conditions at least 48h apart, namely anodal-tDCS and sham-tDCS (placebo). The a-tDCS condition targeted the left DLPC (F3) and was applied during 20min using a 2mA current intensity. In the sham-tDCS condition, electrode position remained the same but the stimulator was turned off after 30s. Functional mobility and balance were assessed using the Berg Balance Scale, Dynamic Gait Index and Timed Up and Go. There were significant differences between conditions on all outcome measures, as the a-tDCS condition was associated with better performance in comparison to the sham condition (p<0.05). Our findings suggest that a-tDCS on the left DLPFC improves balance and functional mobility in comparison to sham-tDCS. Compensatory mechanisms that support motor function in individuals with PD may have been enhanced by a-tDCS on the DLPFC, leading to improved functional mobility and balance. Future trials should explore left DLPFC stimulation with larger samples and compare t-DCS protocols targeting several brain regions.

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Previous studies investigating the effects of transcranial direct current stimulation (tDCS) on muscle strength showed no consensus. Therefore, the purpose of this article was to systematically review the literature on the effects of single dose tDCS to improve muscle strength. A systematic literature search was conducted on PubMeb, ISI Web of Science, SciELO, and Scopus using search terms regarding tDCS and muscle strength. Studies were included in accordance with Population, Intervention, Comparison, Outcomes, and Setting (PICOS) including criteria. Healthy men and women, strength training practitioners or sedentary were selected. The acute effects of single dose anode stimulus of tDCS (a-tDCS) and the placebo stimulus of tDCS (sham) or no interventions were considered as an intervention and comparators, respectively. Measures related to muscle strength were analyzed. To conduct the analyses a weighted mean difference (WMD) and the standardized mean difference (SMD) were applied as appropriate. A total of 15 studies were included in this systematic review and 14 in meta-analysis. Regarding the maximal isometric voluntary contraction (MIVC), a small effect was seen between tDCS and Sham with significant difference between the conditions (SMD = 0.29; CI95% = 0.05 to 0.54; Z = 2.36; p = 0.02). The muscular endurance measured by the seconds sustaining a percentage of MIVC demonstrated a large effect between tDCS and Sham (WMD = 43.66; CI95% = 29.76 to 57.55; Z = 6.16; p < 0.001), showing an improvement in muscular endurance after exposure to tDCS. However, muscular endurance based on total work showed a trivial effect between tDCS and Sham with no significant difference (SMD = 0.22; CI95% = -0.11 to 0.54; Z = 1.32, p = 0.19). This study suggests that the use of tDCS may promote increase in maximal voluntary contraction and muscular endurance through isometric contractions.

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Rodrigues, GM, Machado, S, Faria Vieira, LA, Ramalho de Oliveira, BR, Jesus Abreu, MA, Marquez, G, Maranhão Neto, GA, and Lattari, E. Effects of anodal transcranial direct current stimulation on training volume and pleasure responses in the back squat exercise following a bench press. J Strength Cond Res 36(11): 3048–3055, 2022—This study aimed to investigate the effects of anodal transcranial direct current stimulation (a-tDCS) on volume-load and pleasure responses in a back squat following a bench press. Twelve male subjects advanced in resistance training (RT) (age, 25.5 ± 4.4 years) completed 2 experimental trials in a counterbalanced crossover design: a-tDCS and sham conditions. The stimulus was applied over the left dorsolateral prefrontal cortex for 20 minutes using a 2-mA current intensity in a-tDCS condition and 1 minute of active stimulus in the sham condition. Immediately after stimulation, subjects performed the bench press followed by the back squat. The exercise protocol consisted of 3 sets of maximum repetitions at an intensity of 80% of 1 repetition maximum. The volume-load, perceived pleasure, and arousal responses were measured during the RT protocol. The results indicated that volume-load was higher in the a-tDCS condition than in the sham condition for both exercises (p = 0.02), with large effect for the back squat (p = 0.045; d = 0.96). The higher volume-load was obtained by increasing the number of repetitions across all sets for the bench press (p ≤ 0.0001) and only in the first set for the back squat (p = 0.01). The circumplex model analysis showed a higher pleasure in the bench press and a tendency toward a higher pleasure in the a-tDCS condition. Anodal tDCS may be used as an ergogenic resource for increasing the back squat volume after performing the bench press in resistance-trained male subjects.

The endocannabinoid system comprises several molecular entities such as endogenous ligands [anandamide (AEA) and 2-arachidonoylglycerol (2-AG)], receptors (CB1 and CB2), enzymes such as [fatty acid amide hydrolase (FAHH) and monoacylglycerol lipase (MAGL)], as well as the anandamide membrane transporter. Although the role of this complex neurobiological system in the sleep–wake cycle modulation has been studied, the contribution of the blocker of FAAH/transient receptor potential cation channel subfamily V member 1 (TRPV1), N-arachidonoyl-serotonin (AA-5-HT) in sleep has not been investigated. Thus, in the present study, varying doses of AA-5-HT (5, 10, or 20 mg/Kg, i.p.) injected at the beginning of the lights-on period of rats, caused no statistical changes in sleep patterns. However, similar pharmacological treatment given to animals at the beginning of the dark period decreased wakefulness (W) and increased slow wave sleep (SWS) as well as rapid eye movement sleep (REMS). Power spectra analysis of states of vigilance showed that injection of AA-5-HT during the lights-off period diminished alpha spectrum across alertness in a dose-dependent fashion. In opposition, delta power spectra was enhanced as well as theta spectrum, during SWS and REMS, respectively. Moreover, the highest dose of AA-5-HT decreased wake-related contents of neurotransmitters such as dopamine (DA), norepinephrine (NE), epinephrine (EP), serotonin (5-HT) whereas the levels of adenosine (AD) were enhanced. In addition, the sleep-inducing properties of AA-5-HT were confirmed since this compound blocked the increase in W caused by stimulants such as cannabidiol (CBD) or modafinil (MOD) during the lights-on period. Additionally, administration of AA-5-HT also prevented the enhancement in contents of DA, NE, EP, 5-HT and AD after CBD of MOD injection. Lastly, the role of AA-5-HT in sleep homeostasis was tested in animals that received either CBD or MOD after total sleep deprivation (TSD). The injection of CBD or MOD increased alertness during sleep rebound period after TSD. However, AA-5-HT blocked this effect by allowing animals to display an enhancement in sleep across sleep rebound period. Overall, our findings provide evidence that AA-5-HT is an important modulator of sleep, sleep homeostasis and neurotransmitter contents.

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