The Effects Of Transcranial Direct Current Stimulation On Handgrip Endurance In Adults Over 60 Years Old

Age-related changes to the neuromuscular system can have a negative effect on motor function and performance, which gradually constrain daily activities and independent living for older adults. The prefrontal cortex manages cognitive control of behavior, by processing internal and external cues related to exercise such as perception of effort and knowledge of exercise endpoint. Anodal transcranial direct current stimulation (a-tDCS) has been linked to improvements in the neuromuscular system by increasing the rate at which neurons fire as well as strengthening synaptic connections. The effects of a-tDCS of the prefrontal cortex on muscular function are not well understood, specifically in adults over 60 years old. PURPOSE: The purpose of this study was to determine if a-tDCS on the prefrontal cortex will improve handgrip time-to-failure in adults over 60 years old. METHODS: In this randomized, single-blinded, cross-over design, 11 participants completed five maximal voluntary contractions, followed by 20 minutes of a-tDCS or SHAM (stimulation is turned off after 30-s) conditions. Next, participants completed a handgrip time-to-failure task by maximally squeezing a handgrip dynamometer until they could no longer maintain 50% of their maximal voluntary contraction. RESULTS: On average, participants tended to maintain 50% of their maximal voluntary contraction for a longer period in a-tDCS condition (Mean ± SD; 78.14 ± 44.05) compared to the SHAM condition (Mean ± SD; 57.75 ± 28.43). However, this difference (20.39, 95% CI [-8.02, 48.8]) was not statistically significant (p = 0.14), and it represented a medium-sized effect (d = 0.65). CONCLUSION: This study provides evidence that a-tDCS does not improve handgrip endurance in older adults. A larger sample size, and incorporating a true control group would improve the quality of this study. This finding adds contrasting evidence regarding the ergogenic effects of an acute session of a-tDCS. Further research is needed to confirm the performance-enhancing effects of a single session of a-tDCS. College of Graduate Research and Studies at Northern Michigan University Excellence In Education Grant