The additive effect of neuromuscular electrical stimulation and resistance training on muscle mass and strength.

Purpose: To compare strength and muscle mass development between conventional resistance training (RT) and a combined resistance training with neuromuscular electrical stimulation group (RT + NMES).

Methods: Searches of EBSCO, GoogleScholar, PubMed, and ResearchGate were conducted for studies that met the inclusion criteria of being a randomized controlled trial comparing RT in isolation with NMES and RT being done simultaneously. Effect sizes were calculated as the standard mean difference (SMD) and meta-analyses were computed using random effects models. Thirteen studies were included in the analyses.

Results: When comparing strength gain, there was a favorable effect towards superimposed training (SMD: 0.31; 95% CI 0.13-0.49; p = 0.02; I² = 73.05%) with similar results seen for muscle mass (SMD: 0.26; 95% CI 0.04-0.49; p = 0.02; I² = 21.45%).

Conclusion: Use of NMES during RT results in greater gains in strength and muscle mass compared to RT performed in isolation. Incorporation of NMES into RT protocols may represent a more effective strategy to improve muscle strength and muscle mass. Future studies should explore whether use of NMES concurrently with RT may have additive effects on metabolic and/or cardiovascular health.