Discover how combining NMES with resistance training boosts muscle strength and mass. Game-changing fitness strategy.
The use of a portable, non-invasive electrical muscle stimulator during resistance training has been found to enhance muscle strength and mass more effectively than resistance training alone, as indicated by recent research.
Resistance training, which involves muscle contractions against external resistance, remains a well-established method for improving skeletal muscle mass, strength, and power. Similarly, the application of a widely accessible neuromuscular electrical stimulation (NMES) device to generate involuntary muscle contractions has demonstrated benefits in increasing strength and mass across both upper and lower body muscles.
A study led by researchers at the University of Texas at El Paso (UTEP) explored the combined impact of resistance training (RT) and NMES on muscle development.
“To our knowledge, there are no systematic review and meta-analysis studies to date that evaluate the effectiveness of using NMES with RT,” stated the research team. “To address this gap, this systematic review and meta-analysis aimed to assess the effect of superimposed NMES on resistance training-induced increases in muscle strength and muscle mass compared to conventional RT.”
An analysis of 13 randomized controlled trials and intervention studies examined the effects of NMES devices when combined with traditional resistance exercises such as bench presses and squats. A total of 374 participants, all without neurological or muscular impairments, were included in these studies.
“A meta-analysis provides more comprehensive evidence on studies that explore the same research question,” stated Sudip Bajpeyi, PhD, director of the Metabolic, Nutrition, and Exercise Research (MiNER) Laboratory at UTEP’s Department of Kinesiology and the study’s corresponding author. “This approach allows us to move beyond the limitations of individual studies and make them more informed, evidence-based conclusions.”
In a meta-analysis of 12 studies comparing muscular strength improvements between NMES plus RT groups and those engaging in conventional RT, a standardized mean difference (SMD) of 0.31 was observed. Understanding this figure requires an explanation of the SMD’s significance.
A SMD serves as a summary statistic in meta-analyses when multiple studies assess the same outcome using different measurement methods. Standardization ensures that results from various studies can be aggregated into a single value. A SMD of zero would indicate no advantage for those exposed to an intervention, while a value above or below zero signifies a positive or negative effect, depending on the outcome being measured.
In the present study, a standardized mean difference (SMD) of 0.31 suggests that participants undergoing NMES combined with RT experienced greater improvements in muscle strength compared to those engaging in conventional RT alone. A similar trend was observed for muscle mass, with a SMD of 0.26, indicating an increase in mass when NMES was incorporated into RT. Notably, the researchers found that an NMES-RT combination lasting eight to sixteen weeks led to greater muscle mass gains compared to shorter durations of two to eight weeks.
“Therefore, it may be possible that a minimum of 8 weeks of training duration is necessary to see significant improvement in muscle mass between the two modes of exercise,” stated the researchers.
To assess potential influences of NMES or RT on muscle strength and mass, a sensitivity analysis was conducted. Increased muscular strength was associated with RT variables such as the number of sets and repetitions per set. For NMES, stimulation frequencies of 85 Hz or higher were linked to strength gains. Additionally, factors such as weekly training frequency, total sessions, and overall training duration showed a positive correlation with strength improvements. However, none of these variables appeared to influence the muscle mass increases observed in the study.
“This is the first systematic review and meta-analysis that has investigated whether the additions of NMES to a [sic] RT intervention leads to greater gains in muscle strength compared to RT performed alone,” the researchers stated. “The results indicate a significantly greater increase in muscle strength when NMES is superimposed on RT compared to RT performed alone.”
Notably, none of the studies accounted for dietary intake. Adequate protein consumption plays a crucial role in increasing muscle strength and size by promoting muscle protein synthesis while reducing its breakdown, resulting in a net positive muscle protein balance. Due to this lack of dietary control, the potential influence of nutrition remains uncertain. Further research, ideally with a larger sample size, is necessary to explore this factor and produce more statistically significant findings.
Despite certain limitations, these findings hold particular relevance for individuals seeking to enhance muscle function and strength following surgery or extended periods of inactivity due to illness.
“RT has long been recommended for improving muscle strength and muscle mass,” the researchers noted. “NMES is commonly used in therapeutic and rehabilitative settings to prevent the loss of muscle strength and muscle mass during immobilization and physical inactivity. NMES is also practical and convenient to use due to the cost, portability and minimal equipment and effort required to receive the benefits associated with it.”
https://doi.org/10.1007/s00421-024-05700-2
Abstract
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.