Protection against muscle damage induced by electrical stimulation: efficiency of a preconditioning programme

The effect of neuromuscular electrical stimulation applied at different muscle lengths on muscle architecture and sarcomere morphology in rats

Neuromuscular electrical stimulation (NMES) is often used to increase muscle strength and functionality. Muscle architecture is important for the skeletal muscle functionality. The aim of this study was to investigate the effects of NMES applied at different muscle lengths on skeletal muscle architecture. Twenty-four rats were randomly assigned to four groups (two NMES groups and two control groups). NMES was applied on the extensor digitorum longus muscle at long muscle length, which is the longest and stretched position of the muscle at 170° plantar flexion, and at medium muscle length, which is the length of the muscle at 90° plantar flexion. A control group was created for each NMES group. NMES was applied for 8 weeks, 10 min/day, 3 days/week. After 8 weeks, muscle samples were removed at the NMES intervention lengths and examined macroscopically, and microscopically using a transmission electron microscope and streo-microscope. Muscle damage, and architectural properties of the muscle including pennation angle, fibre length, muscle length, muscle mass, physiological cross-sectional area, fibre length/muscle length, sarcomere length, sarcomere number were then evaluated. There was an increase in fibre length and sarcomere number, and a decrease in pennation angle at both lengths. In the long muscle length group, muscle length was increased, but widespread muscle damage was observed. These results suggest that the intervention of NMES at long muscle length can increase the muscle length but also causes muscle damage. In addition, the greater longitudinal increase in muscle length may be a result of the continuous degeneration-regeneration cycle.

Neuromuscular electrical stimulation and protein during bed rest increases CD11b+ skeletal muscle macrophages but does not correspond to muscle size or insulin sensitivity

With this cohort, we previously demonstrated preservation of thigh lean tissue with neuromuscular electrical stimulation combined with protein supplementation (NMES+PRO) treatment during bed rest in healthy older adults. Because macrophage polarization plays a significant role in the repair and maintenance of muscle size and insulin sensitivity, we hypothesized that muscle macrophages would be induced by NMES+PRO and would correspond to an increase in lean mass and an attenuated insulin resistance response altered by bed rest. Older adults (60-80 years old; body mass index < 30 kg/m2) underwent 5 days of bed rest and were randomized to either thrice daily treatment of NMES+PRO (n = 8) or CON (n = 8). Lean mass, insulin sensitivity, and markers of muscle macrophages, inflammation, and connective tissue were determined before and after bed rest. Glucose intolerance and insulin resistance occurred after bed rest but there was not a treatment effect (p > 0.10). Proinflammatory-like macrophages (CD11b+, CD206-) increased (p < 0.05) with NMES+PRO treatment and was different than CON. Minor changes in noncontractile tissue were observed. However, changes in muscle macrophages or extracellular matrix were not related to the preservation of thigh lean mass or insulin resistance. Daily NMES+PRO treatment during bed rest induced a muscle proinflammatory-like macrophage response and was unrelated to muscle size or metabolic function. This study is listed as clinical trial NCT02566590. Novelty Neuromuscular electrical stimulation combined with protein supplementation (NMES+PRO) increased proinflammatory-like macrophages and extracellular matrix content in older adults after bed rest. NMES+PRO changes in macrophages and noncontractile tissue macrophages were not related to muscle size preservation or insulin sensitivity.

The effect of low level laser irradiation on oxidative stress, muscle damage and function following neuromuscular electrical stimulation. A double blind, randomised, crossover trial

Background

Low level laser therapy (LLLT) is among novel methods for preventing and treating muscle damage and soreness induced by volitional exercise, but little is known about using LLLT before neuromuscular electrical stimulation. The aim of this first randomised, double blind, crossover trial addressing this issue was to evaluate effects of LLLT on muscle damage and oxidative stress, as well as recovery of muscle function after a single session of isometric neuromuscular electrical stimulation(NMES).

Methods

Twenty four moderately active, healthy men aged 21–22 years received 45 electrically evoked tetanic, isometric contractions of the quadriceps femoris, preceded by LLLT or sham-LLLT. Maximal isometric voluntary muscle torques, perceived soreness, and blood samples were analysed from baseline to 96 h post intervention. We measured plasma markers of muscle damage (the activity of creatine kinase), and inflammation (C-reactive protein), and evaluated redox state parameters.

Results

NMES-evoked contractions induced oxidative stress, demonstrated by an increase in lipid peroxidation and impairments in enzymatic antioxidant system. LLLT irradiations had a protective effect on NMES-induced decrease in enzymatic antioxidant defence and shortened the duration of inflammation. This effect of irradiations on redox state and inflammation did not affect lipid peroxidation, muscle damage, and muscle torque.

Conclusions

LLLT may protect from impairments in enzymatic antioxidant system and may shorten inflammation induced by a single NMES session in moderately active, healthy men. However, the effects of LLLT on redox state and inflammatory processes do not seem to affect muscle damage and recovery of muscle function after NMES.

Trial registration

The study was retrospectively registered in the Australian New Zealand Clinical Trials Registry (ANZCTR); The trial registration number: ACTRN12619000678190; date of registration: 6 May 2019.

Effects of whole-body ELECTROMYOSTIMULATION on health and performance: a systematic review

BACKGROUND

Whole-body electrical myostimulation (WB-EMS) is a relatively recent training methodology that has been extraordinarily used in recent years. However, there is a lack of consensus on the effectiveness of WB-EMS in the situations in which its use has been largely popularized. The objective of this systematic review was to determine the effects produced by WB-EMS.

METHODS

A search of PubMed, Web of Science, Scopus and Cochrane was performed to identify all the studies that have applied electrical stimulation in lower and upper limbs simultaneously and that have clearly presented their protocols for the training and application of the stimulation. The last search was performed on September 9, 2018. Studies written in English or German were included.

RESULTS

A total of 21 articles met the inclusion criteria and were analyzed following the guidelines of the Cochrane Guide for Systematic Reviews. Nineteen studies analyzed the chronic effects of WB-EMS, and 2 analyzed acute effects with a total of 505 subjects (310 men and 195 women). In total, 35% were moderately trained, and 65% were sedentary subjects. Different dependent variables were studied, such as anthropometric parameters, strength parameters, energy expenditure, psychophysiological parameters and blood parameters. There is a lack of randomized controlled studies, and the studies included exhibit a moderate to high level of risk of bias.

CONCLUSIONS

Given the limited number of available studies on WB-EMS, the scarce amount of scientific evidence found does not allow definitive conclusions about its effects; therefore, future studies about WB-EMS are necessary.

Can the Use of Neuromuscular Electrical Stimulation Be Improved to Optimize Quadriceps Strengthening?

CONTEXT

Neuromuscular electrical stimulation (NMES) is a common modality used to retrain muscles and improve muscular strength after injury or surgery, particularly for the quadriceps muscle. There are parameter adjustments that can be made to maximize the effectiveness of NMES. While NMES is often used in clinical practice, there are some limitations that clinicians should be aware of, including patient discomfort, muscle fatigue, and muscle damage.

EVIDENCE ACQUISITION

PubMed was searched through August 2014 and all articles cross-referenced.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 3.

RESULTS

Clinicians can optimize torque production and decrease discomfort by altering parameter selection (pulse duration, pulse frequency, duty cycle, and amplitude). Pulse duration of 400 to 600 μs and a pulse frequency of 30 to 50 Hz appear to be the most effective parameters to optimize torque output while minimizing discomfort, muscle fatigue, or muscle damage. Optimal electrode placement, conditioning programs, and stimulus pattern modulation during long-term NMES use may improve results.

CONCLUSION

Torque production can be enhanced while decreasing patient discomfort and minimizing fatigue.