NEUROMUSCULAR FATIGUE AFTER LOW- AND MEDIUM-FREQUENCY ELECTRICAL STIMULATION IN HEALTHY ADULTS

Introduction: In this study we investigated fatigue origins induced by low-frequency pulsed current (PC) and medium-frequency current (MF) neuromuscular electrical stimulation (NMES) after a clinical-like session. Methods: Eleven healthy men randomly underwent 2 NMES sessions, PC and MF, on quadriceps muscle (15-minute duration, 6 seconds on and 18 seconds off). Maximal voluntary contraction (MVC), central activation ratio (CAR), vastus lateralis electromyographic activity (EMG), and evoked contractile properties were determined before and after the sessions. Evoked torque and discomfort during the sessions were also measured. Results: Both currents produced decreases in MVC, EMG, and evoked contractile properties after the sessions. No difference was found between currents for all variables (P>0.05). Evoked torque during sessions decreased (P<0.05). No difference was observed in mean evoked torque and discomfort (P>0.05). Discussion: Both currents induced similar neuromuscular fatigue. Clinicians can choose either PC or MF and expect similar treatment effects when the goal is to generate gains in muscle strength.