Combining Weight Training with Electrical Stimulation Boosts Muscle Growth and Strength

New research suggests that using a standard, portable, non-invasive electrical muscle stimulator during resistance training can lead to greater improvements in both muscle strength and mass compared to resistance training alone.

Traditional resistance training, which involves exercises that make muscles contract against external resistance, enhances skeletal muscle mass, strength, and power. Similarly, using a commonly available, non-invasive neuromuscular electrical stimulation (NMES) device to trigger involuntary muscle contractions can also boost strength and mass in both upper and lower body muscles.

Researchers from the University of Texas at El Paso (UTEP) recently conducted a study to explore the combined effects of resistance training (RT) and neuromuscular electrical stimulation (NMES) on muscle mass and strength.

“To our knowledge, no systematic reviews or meta-analyses have yet evaluated the effectiveness of combining NMES with RT,” the researchers noted. “To fill this gap, our systematic review and meta-analysis aimed to assess how superimposed NMES influences the muscle strength and mass gains from resistance training, compared to conventional RT alone.”

Review of Studies on NMES and Resistance Training

The researchers reviewed 13 randomized controlled trials and intervention studies involving 374 participants who used an NMES device while performing traditional resistance exercises, such as bench presses and squats. These studies were conducted on healthy individuals without neurological or muscular impairments.

“A meta-analysis provides a more comprehensive view of studies addressing the same research question,” explained Sudip Bajpeyi, PhD, director of the Metabolic, Nutrition, and Exercise Research (MiNER) Laboratory at UTEP and the study’s lead author. “This approach allows us to overcome the limitations of individual studies and draw more informed, evidence-based conclusions.”

In their meta-analysis of 12 studies comparing muscular strength improvements between NMES-plus-RT groups and those doing conventional RT, the researchers found a standardized mean difference (SMD) of 0.31 across all studies. However, understanding the significance of this figure and the use of SMD requires further explanation.

A standardized mean difference (SMD) is used in meta-analyses when different studies assess the same outcome but measure it in various ways. To enable comparisons across studies, the results must first be standardized to a common measurement. Once standardized, the results are combined in the meta-analysis to generate a single value, the SMD.

Understanding the Standardized Mean Difference (SMD)

However, the SMD is not tied to a specific unit of measurement. If the SMD is zero, it suggests that the intervention had no effect compared to the control. A positive or negative SMD indicates a favorable or unfavorable result, depending on the outcome being measured. For a more detailed explanation of SMDs, the video below offers additional insight.

NMES and RT Combination Improves Muscle Strength and Mass

The study found that combining NMES with RT led to greater muscle strength (SMD of 0.31) and muscle mass (SMD of 0.26) compared to conventional RT. Muscle mass gains were higher with 8–16 weeks of combined training versus 2–8 weeks. The researchers suggest that at least eight weeks of training may be needed for significant muscle mass improvements.

A sensitivity analysis revealed that RT variables, such as sets and repetitions, and NMES frequencies of 85 Hz or higher were linked to increased muscle strength. Overall, factors like session frequency and duration positively influenced strength but not muscle mass.

“This is the first meta-analysis to examine if adding NMES to RT boosts muscle strength more than RT alone,” the researchers concluded, noting a significant increase in strength with the NMES-RT combination.

None of the studies controlled participants’ diets, which are crucial for muscle growth. Protein intake is key for muscle strength and size, promoting protein synthesis and preventing breakdown. Without diet control, its impact remains uncertain, and further research with a larger sample size is needed.

Despite these limitations, the researchers highlight the relevance of their findings, especially for those aiming to improve muscle function and strength after surgery or illness.

“RT is recommended for boosting muscle strength and mass,” they said. “NMES is commonly used in therapy to prevent muscle loss during inactivity and is practical due to its cost-effectiveness and ease of use.”

Read the original article on: New Atlas

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