Transcutaneous Spinal Direct Current Stimulation And Dorsiflexor Muscle Performance In Humans

Transcutaneous Spinal Direct Current Stimulation and dorsiflexor muscle performance in humans Author block: Andrea Gigliotti, Blake A. Renken, Emily F. Battung, Hugo M. Pereira Previous studies suggest that Transcutaneous spinal direct current stimulation (TSDCS) can potentially modulate spinal neurons, however, any benefit of TSDCS on motor performance of the lower limbs is not fully understood. PURPOSE: To determine the effect of anodal and cathodal TSDCS on motor performance of the dorsiflexor muscles and potential physiological mechanisms involved. METHODS: 12 participants (age: 26 ± 3 years old; 4 male, 8 female) performed maximal and submaximal isometric contractions with the dorsiflexor muscles of the non-dominant leg in 3 randomized test sessions (anodal, cathodal and sham TSDCS, separated by at least 48 hours) performed after a familiarization session. For each test session, and before the muscle contractions, individuals received a different type of TSDCS at 2.5 mA for 15 min (current density: 0.071 mA/cm2) delivered at thoracic level (T10). Transcranial magnetic stimulation (TMS) and peripheral nerve stimulation were used to quantify Motor Evoked Potentials and M-waves. RESULTS: Maximal voluntary contraction (MVC) was similar for anodal, cathodal or sham TSDCS sessions (44.8 ± 15 vs. 43 ± 16 vs 45.7 ± 15 Nm, respectively; session effect: P = 0.09). The type of TSDCS stimulation did not alter the maximum rate of torque development at either 50, 100, and 200 ms (session effect: P > 0.05 for all time points). Steadiness quantified with the coefficient of variation of force was similar across anodal, cathodal and sham sessions at 5% of MVC (5 ± 2 vs. 5 ± 1 vs. 5 ± 1 %; Session effect: P = 0.33) or 10% of MVC (3 ± 1 vs. 3 ± 1 vs. 3 ± 1%, respectively; session effect: P = 0.40). M-waves (P = 0.65) and Active Motor Thresholds were similar across anodal, cathodal, and sham sessions (44.8 ± 9 vs. 43.9 ± 7 vs. 43.5 ± 9 % stimulator output, respectively; session effect: P = 0.53). Motor evoked potentials at 120% of active motor threshold were similar for anodal, cathodal and sham TSDCS (28 ± 11 vs. 37.6 ± 18 vs. 32 ± 11 % of M-max; session effect: P = 0.23). CONCLUSION: This preliminary data suggests that TSDCS did not influence dorsiflexor muscles maximal or submaximal isometric contractions in healthy young individuals.