Russian and Low-Frequency Currents Induced Similar Neuromuscular Adaptations in Soccer Players: A Randomized Controlled Trial

Context: Neuromuscular electrical stimulation is widely used to induce muscular strength increase; however, no study has compared Russian current (RC) with pulsed current (PC) effects after a training program. Objectives: We studied the effects of different neuromuscular electrical stimulation currents, RC, and PC on the neuromuscular system after a 6-week training period. Design: Blinded randomized controlled trial. Setting: Laboratory. Patients: A total of 27 male soccer players (age 22.2 [2.2] y, body mass 74.2 [10.0] kg, height 177 [0] cm, and body mass index 23.7 [2.9] kg/cm(2) for the control group; 22.1 [3.1] y, 69.7 [5.7] kg, 174 [0] cm, and 23.0 [2.5] kg/cm for the PC group; and 23.0 [3.4] y, 72.1 [10.7] kg, 175 [0] cm, and 23.5 [3.4] kg/cm for the RC group) were randomized into 3 groups: (I) control group; (2) RC (2500 Hz, burst 100 Hz, and phase duration 200 mu s); and (3) PC (100 Hz and 200 mu s). Intervention: The experimental groups trained for 6 weeks, with 3 sessions per week with neuromuscular electrical stimulation. Main Outcome Measures: Maximal voluntary isometric contraction and evoked torque, muscle architecture, sensory discomfort (visual analog scale), and electromyographic activity were evaluated before and after the 6-week period. Results: Evoked torque increased in the RC (169.5% [78.2%]. P < .01) and PC (248.7% [81.1%], P < .01) groups. Muscle thickness and pennation angle increased in the RC (8.7% [3.8%] and 16.7% [9.0%], P < .01) and PC (16.1% [8.0%] and 27.4% [11.0%], P < .01) groups. The PC demonstrated lower values for visual analog scale (38.8% [17.1%], P < .01). There was no significant time difference for maximal voluntary isometric contraction and root mean square values (P> .05). For all these variables, there was no difference between the RC and PC (P> .05). Conclusion: Despite the widespread use of RC in clinical practice, RC and PC training programs produced similar neuromuscular adaptations in soccer players. Nonetheless, as PC generated less perceived discomfort, it could be preferred after several training sessions.