Transcranial direct current stimulation (tDCS) has been applied in training and competition, but its effects on physical performance remain largely unknown. This study aimed to observe the effect of tDCS on muscular strength and knee activation. Nineteen healthy young men were subjected to 20 min of real stimulation (2 mA) and sham stimulation (0 mA) over the primary motor cortex (M1) bilaterally on different days. The maximal voluntary contraction (MVC) of the knee extensors and flexors, and surface electromyography (sEMG) of the rectus femoris (RF) and biceps femoris (BF) were recorded before, immediately after, and 30 min after stimulation. MVC, rate of force development (RFD), and sEMG activity were analyzed before and after each condition. MVC of the non-dominant leg extensor and flexor was significantly higher immediately after real stimulation and 30 min after stimulation than before, and MVC of the non-dominant leg flexor was significantly higher 30 min after real stimulation than that after sham stimulation (P < 0.05). The RFD of the non-dominant leg extensor and flexor immediately after real stimulation was significantly higher than before stimulation, and the RFD of the non-dominant leg extensor immediately after real stimulation and 30 min after stimulation was significantly higher than that of sham stimulation (P < 0.05). EMG analysis showed the root mean square amplitude and mean power frequency (MPF) of the non-dominant BF and RF were significantly higher immediately after real stimulation and 30 min after stimulation than before stimulation, and the MPF of the non-dominant BF EMG was significantly higher 30 min after real stimulation than that after sham stimulation (P < 0.05). Bilateral tDCS of the M1 can significantly improve the muscle strength and explosive force of the non-dominant knee extensor and flexor, which might result from increased recruitment of motor units. This effect can last until 30 min after stimulation, but there is no significant effect on the dominant knee.

ObjectiveWhether transcranial direct current stimulation (tDCS) can improve upper limb muscle strength and endurance in healthy subjects is still controversial. This article reviews the relevant literature on the use of tDCS to improve upper limb muscle strength and endurance in healthy individuals.MethodsWe systematically searched the Cochrane Library, PubMed, EMBASE, and the Web of Science until September 4, 2021. Randomized parallel or crossover experimental studies on the effects of tDCS on upper limb muscle strength and endurance in healthy individuals were included. Review Manager 5.3 software was used to evaluate methodological quality and analyze the combined effect of the included literature.ResultsTwelve studies (189 participants) were included in the qualitative synthesis, and nine studies (146 participants) were included in the meta-analysis. Compared with the control group, the tDCS intervention had no significant effect on improving upper limb muscle strength [I2 = 0%, 95% CI (−0.79, 0.23), p = 0.98, MD = 0.01]. In this analysis, tDCS had a significant heterogeneity (I2 = 87%) in improving upper limb muscle endurance compared with the control group. After the subgroup analysis and the sensitivity analysis, the source of heterogeneity was excluded. The final results showed that tDCS had a significant effect on improving upper limb muscle endurance [I2 = 0%, 95% CI (1.91, 4.83), p < 0.00001, MD = 3.37].ConclusionstDCS has no significant effect on improvement of upper limb muscle strength, but has a significant effect on improving upper limb endurance performance (especially on the non-dominant side).

Objective:Previous behavioral studies have reported the potential of transcranial alternating current stimulation in analyzing the causal relationship between neural activity and behavior. However, the efficacy of tACS on motor performance and learning in healthy individuals remains unclear. This systematic reviewexamines the effectiveness of tACS on motor performance and motor learning in healthy individuals.Methods: Literature was systematically searched through the Cochrane Library, PubMed, EMBASE, and Web of Science until 16 October 2022. Studies were eligible for review if they were randomized, parallel, or crossover experimental designs and reported the efficacy of tACS on motor performance and motor learning in healthy adults. Review Manager 5.3 was used to evaluate the methodological quality and analyze the combined effect.Results: Ten studies (270 participants) met all the inclusion criteria. The results showed that motor performance was not significantly greater than that with sham tACS stimulation [I2 = 44%, 95% CI (–0.01, 0.35), p = 0.06, standardized mean difference = 0.17], whereas motor learning ability improved significantly [I2 = 33%, 95% CI (−1.03, −0.31), p = 0.0002, SMD = −0.67]. Subgroup analysis found that gamma bend tACS could affect the changes in motor performance (I2 = 6%, 95% CI (0.05, 0.51), p = 0.02, SMD = 0.28), and online tACS did as well [I2 = 54%, 95% CI (0.12, 0.56), p = 0.002, SMD = 0.34].Conclusion: The results showed that tACS effectively improves motor performance (gamma band and online mode) and motor learning in healthy individuals, which indicates that tACS may be a potential therapeutic tool to improve motor behavioral outcomes. However, further evidence is needed to support these promising results.Systematic Review Registration: PROSPERO, identifier CRD42022342884

Purpose: Brain source mechanisms of the cortical EEG brainwave at the resting state in the elderly during normal aging are rarely known.To solve the problem, we use a standard low-resolution electromagnetic tomography to explore the brain source mechanisms on the effects of healthy aging on brain function at the resting state.Methods: Eye-closed EEG signals at resting state were sampled in 13 normal elderly adults and 17 normal young adults. The EEG rhythms by frequency band, delta, theta, alpha 1, alpha 2, beta 1, and beta 2 were of interest for this analysis. Brain sources of these rhythms were estimated by standard low-resolution electromagnetic tomography.Results: Statistical results demonstrated that central, parietal, occipital, and temporal alpha 1 and theta brain sources presented the pattern normal young adults . normal elderly adults (P , 0.05), whereas the global beta 1 and beta 2 brain sources presented the pattern normal elderly adults . normal young adults (P , 0.05). Moreover, the same is true that amplitude of central, parietal, occipital, and temporal alpha 2 brain sources were lower in normal elderly adults compared with those in normal young adults (P , 0.05).Conclusions: These results imply that normal aging is linked to cortical neural desynchronization of alpha and delta rhythms and synchronization of beta rhythm in central, parietal, and frontal cortices at resting state.