The acute effects of transcranial direct current stimulation on the performance of velocity based squat training

Abstract

Transcranial direct current stimulation (tDCS) has emerged as a promising neuromodulatory technique for improving sports performance, especially in reducing speed loss during overloaded exercise. This effect is mainly attributed to the ability of tDCS to modulate the cerebral cortex, influencing motor response and fatigue resistance. However, it is still unclear which cortical area is optimal for stimulation, as there is limited and inconclusive evidence comparing different brain regions. The primary objective of this thesis was to investigate the effects of anodal tDCS applied to two distinct cortical areas-the dorsolateral prefrontal cortex (DLPFC) and the primary motor cortex (M1)-on performance metrics during speed-based training. Specifically, we examined the impact on the number of repetitions completed, movement speed, and perception of effort during squat exercise. Fifteen healthy men (mean age 21.8 ± 2.6 years) participated in this randomized, double-blind, cross-sectional study. Each participant attended three separate experimental sessions, receiving in each 20 minutes of anodic tDCS (2.0 mA) targeted to either bilateral M1, DLPFC or sham stimulation (SHAM) as a control condition. Following stimulation, participants performed squats, continuing each set until a 15% loss in movement velocity was detected, ensuring consistent fatigue levels between sets. A total of five sets were completed, with standardized 90-second rest intervals to monitor recovery. Performance results were assessed by recording the number of repetitions completed in each set and measuring average propulsive velocities using a linear position transducer. In addition, participants reported their perception of exertion using the OMNI-RES scale immediately after each set in order to assess subjective levels of fatigue and exertion. The results indicated that thirteen of the fifteen participants showed a significant increase in the total number of repetitions across all sets when tDCS was applied to the DLPFC or M1 compared to the SHAM condition (p = 0.025). Importantly, this improvement in performance did not correspond with significant changes in mean propulsive velocities or levels of perceived exertion, suggesting that tDCS may specifically increase endurance capacity without altering subjective fatigue or movement speed. These findings suggest that anodic tDCS applied to both DLPFC and M1 can effectively improve performance in squat training, allowing athletes to perform more repetitions at a given intensity without additional perceived exertion or loss of movement speed. This has practical implications for sports training, indicating that tDCS could be a valuable tool for improving muscular endurance and overall performance in overloaded exercise at high intensity. Further research is warranted to explore the underlying neural mechanisms and determine long-term effects and potential applications in various athletic populations.