Comparison of short-term training effects of two neuromuscular electrical stimulation modalities on muscle functions and mass

Purpose: The present study thus aimed to compare the effects of neuromuscular electrical stimulation (NMES) training, using alternating current (AC) and pulsed current (PC), on muscle function and muscle mass. Methods: Twenty-thee healthy male university students (age: 22.68 ± 3.7) were enrolled in this study and divided into two groups (AC = 12, PC = 11) to receive NMES training in both legs simultaneously. Each group underwent a 20-min NMES session using AC or PC, 2 days a week for 5 weeks. AC was delivered at 2.5 kHz (burst frequency: 75 Hz and pulse duration: 400 μs) for the knee extensors of both legs, and PC was delivered at 75 Hz (pulse duration: 400 μs), inducing 60 isometric contractions (on–off ratio: 5–15 s) at a knee joint angle of 100° (0° = full extension). Muscle strength, power, and mass were assessed 1 week before and 1 and 6 weeks after the training program. Results: Findings show a significant increase in vertical jump height after both NMES training, although no torque gain was detected regardless of the type of modality. A significant increase in the region fat-free mass (trained legs) in both NMES currents without a difference between them was observed in the function of the trained muscles. Conclusion: Short-term training (5 weeks) using AC or PC could be insufficient to detect an improvement in muscle functions such as torque gain. However, the short-term training using AC may improve physical performance and body composition.