Effects of neuromuscular electrical stimulation on energy expenditure and postprandial metabolism in healthy men

Muscle Metabolism During Multiple Muscle Stimulation Using an Affordable Equipment

Background/Objectives: Previous studies have shown that neuromuscular electrical stimulation (NMES), while expensive, can provide some of the health benefits of exercise to people who cannot exercise their legs normally. The aim of this study was to quantify the increases in muscle metabolism in four muscles of the legs of able-bodied individuals with NMES. Methods: Healthy college-aged students were tested. NMES of four muscle groups was performed with inexpensive stimulators and reusable tin foil electrodes. The biceps femoris, vastus lateralis, medial gastrocnemius, and tibialis anterior muscles on one leg were stimulated for ten minutes with twitch stimulations at the highest comfortable stimulation current. Muscle metabolism was measured using the slope of oxygen consumption measured with near-infrared spectroscopy (NIRS) during 5 s of cuff ischemia. Results: Initial studies found fold increases in muscle metabolism above rest of 8.9 ± 8.6 for the vastus lateralis, 7.9 ± 11.9 for the biceps femoris, 6.6 ± 7.8 for the medial gastrocnemius, and 4.9 ± 3.9 for the tibialis anterior. Some participants were able to obtain large increases in muscle metabolism, while other participants had lower increases. Conclusions: The ability to produce large increases in metabolism has the potential to allow NMES to replace or augment exercise to improve health in people who cannot otherwise exercise. The devices used were inexpensive and could be adapted for easy use by a wide range of individuals.

Effect of blood flow restriction and electrical muscle stimulation on human glycemic response to a glucose challenge

PURPOSE

To determine whether reduced tissue oxygen availability through blood flow restriction (BFR) alone, or in combination with electrically induced muscle contractions, can improve glucose clearance after an acute glucose challenge.

METHODS

In a randomized crossover design, 21 young participants (females: 12) were allocated to perform 1) electrical muscle stimulation (EMS), 2) BFR, 3) EMS + BFR or 4) no treatment (control). Participants completed each condition immediately preceding a 2 h oral glucose tolerance test (100 g). Primary analyses were performed on the glucose area under the curve (AUC) at time points 0-30, 30-120, and 0-120 min. Secondary analyses were performed on glycemic responses based on biological sex and estimated muscle phenotype.

RESULTS

Compared to the control (322±25 mM∙min), the 0-30 min AUC was reduced following EMS (293±22 mM∙min, p = 0.0004), and EMS + BFR (298±36 mM∙min., p = 0.006), whereas BFR in isolation did not differ (306±30 mM∙min, p = 0.1). The 30-120 and 0-120 min glucose AUCs were similar across conditions. Based on effect size from the control conditions, our secondary analysis suggests different 0-30 min glycemic responses after EMS + BFR between females (dz = 0.206) vs. males (dz = 1.461) and/or slow (dz = 0.426) vs. fast (dz = 1.075) muscle phenotype.

CONCLUSION

Reducing tissue oxygen availability with BFR did not augment the effects of EMS in the overall group; however, we provide preliminary data to suggest possible sex and/or muscle phenotypic responses in glycemic regulation with these modalities.

Effects of neuromuscular electrical stimulation on glycemic control: a systematic review and meta-analysis

Background

Physical inactivity increases the risk for metabolic diseases such as obesity and type 2 diabetes. Neuromuscular electrical stimulation (NMES) is an effective method to induce muscle contraction, particularly for populations with physical impairments and/or metabolic diseases. However, its effectiveness to improve glycemic control is unclear. This review aimed to determine the effectiveness of NMES on glycemic control.

Methods

Electronic search consisted of MEDLINE (PubMed), EMBASE, Cochrane Library, Google Scholar, and Web of Science to identify studies that investigated the effects of NMES on glycemic control for this systematic review. The meta-analysis consists of the studies designed as randomized controlled trials. Effect sizes were calculated as the standardized mean difference (SMD) and meta-analysis was conducted using a random-effects model.

Results

Thirty-five studies met the inclusion criteria for systematic review and of those, nine qualified for the meta-analysis. Existing evidence suggested that NMES effectively improves glycemic control predominantly in middle-aged and elderly population with type 2 diabetes, obesity, and spinal cord injury. The meta-analysis is comprised of 180 participants and reported that NMES intervention lowered fasting blood glucose (SMD: 0.48; 95% CI: 0.17 to 0.78; p=0.002; I²=0%). Additional analysis using the primary measures reported by each study to indicate glycemic control (i.e., OGTT, HOMA-IR, and fasting glucose) also confirmed a significant effect of NMES on improving glycemic control (SMD: 0.41; 95% CI, 0.09 to 0.72; p=0.01; I²=11%). NMES protocol varied across studies and requires standardization.

Conclusion

NMES could be considered as a therapeutic strategy to improve glycemic control in populations with physical impairments and/or metabolic disorders.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42020192491.

Blood flow restriction and stimulated muscle contractions do not improve metabolic or vascular outcomes following glucose ingestion in young, active individuals

Glucose ingestion and absorption into the blood stream can challenge glycemic regulation and vascular endothelial function. Muscular contractions in exercise promote a return to homeostasis by increasing glucose uptake and blood flow. Similarly, muscle hypoxia supports glycemic regulation by increasing glucose oxidation. Blood flow restriction (BFR) induces muscle hypoxia during occlusion and reactive hyperemia upon release. Thus, in the absence of exercise, electric muscle stimulation (EMS) and BFR may offer circulatory and glucoregulatory improvements. In 13 healthy, active participants (27±3yr, 7 female) we tracked post-glucose (oral 100g) glycemic, cardiometabolic and vascular function measures over 120min following four interventions: 1) BFR, 2) EMS, 3) BFR+EMS or 4) Control. BFR was applied at 2min intervals for 30min (70% occlusion), EMS was continuous for 30min (maximum-tolerable intensity). Glycemic and insulinemic responses did not differ between interventions (partial η2=0.11-0.15, P=0.2); however, only BFR+EMS demonstrated cyclic effects on oxygen consumption, carbohydrate oxidation, muscle oxygenation, heart rate, and blood pressure (all P<0.01). Endothelial function was reduced 60min post-glucose ingestion across interventions and recovered by 120min (5.9±2.6% vs 8.4±2.7%; P<0.001). Estimated microvascular function was not meaningfully different. Leg blood flow increased during EMS and BFR+EMS (+656±519mL•min-1, +433±510mL•min-1; P<0.001); however, only remained elevated following BFR intervention 90min post-glucose (+94±94mL•min-1; P=0.02). Superimposition of EMS onto cyclic BFR did not preferentially improve post-glucose metabolic or vascular function amongst young, active participants. Cyclic BFR increased blood flow delivery 60min beyond intervention, and BFR+EMS selectively increased carbohydrate usage and reduced muscle oxygenation warranting future clinical assessments.