Effects of M-Cube Wave Versus Low-Frequency Neuromuscular Electrical Stimulation on the Strength and Thickness of the Quadriceps Muscles: A Within-Subject Comparison in Healthy Young Adults

Background and objectives This study compared the effects of M-cube wave and conventional low-frequency neuromuscular electrical stimulation (NMES) on the strength and thickness of quadriceps muscles in healthy young men using a within-subject design. Materials and methods This study included 15 untrained, healthy young adults. Each participant received two NMES protocols: an M-cube wave protocol on the quadriceps and low-frequency stimulation on the contralateral side. Sessions were performed twice per week for six weeks. Muscle strength was assessed using isometric or concentric maximal voluntary contraction (MVC-ISO and MVC-CON) torque. Muscle thickness of the rectus femoris, vastus lateralis, and vastus intermedius, and subcutaneous fat thickness were measured using ultrasonography. Results Both protocols significantly increased the strength (MVC-ISO: 18.9% vs. 23.3%; MVC-CON: 35.1% vs. 44.8%) and thickness of the quadriceps muscles across all examined muscles. No significant differences were observed between the two NMES waveform protocols. Both groups showed reduced thickness of the subcutaneous fat in the lateral thigh. Conclusion M-cube wave and conventional low-frequency NMES protocols effectively improved the strength and muscle morphology of the quadriceps muscles in healthy young men. These findings support the use of waveforms in clinical and rehabilitative settings, with waveform selection tailored to individual needs and comfort.