Neuromuscular electrical stimulation training induces atypical adaptations of the human skeletal muscle phenotype: a functional and proteomic analysis

Neuromuscular electrical stimulation for muscle weakness in adults with advanced disease

BACKGROUND

This review is an update of a previously published review in the Cochrane Database of Systematic Reviews Issue 1, 2013 on Neuromuscular electrical stimulation for muscle weakness in adults with advanced disease.Patients with advanced progressive disease often experience muscle weakness, which can impact adversely on their ability to be independent and their quality of life. In those patients who are unable or unwilling to undertake whole-body exercise, neuromuscular electrical stimulation (NMES) may be an alternative treatment to enhance lower limb muscle strength. Programmes of NMES appear to be acceptable to patients and have led to improvements in muscle function, exercise capacity, and quality of life. However, estimates regarding the effectiveness of NMES based on individual studies lack power and precision.

OBJECTIVES

Primary objective: to evaluate the effectiveness of NMES on quadriceps muscle strength in adults with advanced disease. Secondary objectives: to examine the safety and acceptability of NMES, and its effect on peripheral muscle function (strength or endurance), muscle mass, exercise capacity, breathlessness, and health-related quality of life.

SEARCH METHODS

We identified studies from searches of the Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Systematic Reviews (CDSR), and Database of Abstracts of Reviews of Effects (DARE) (the Cochrane Library), MEDLINE (OVID), Embase (OVID), CINAHL (EBSCO), and PsycINFO (OVID) databases to January 2016; citation searches, conference proceedings, and previous systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials in adults with advanced chronic respiratory disease, chronic heart failure, cancer, or HIV/AIDS comparing a programme of NMES as a sole or adjunct intervention to no treatment, placebo NMES, or an active control. We imposed no language restriction.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data on study design, participants, interventions, and outcomes. We assessed risk of bias using the Cochrane 'Risk of bias' tool. We calculated mean differences (MD) or standardised mean differences (SMD) between intervention and control groups for outcomes with sufficient data; for other outcomes we described findings from individual studies. We assessed the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

Eighteen studies (20 reports) involving a total of 933 participants with COPD, chronic respiratory disease, chronic heart failure, and/or thoracic cancer met the inclusion criteria for this update, an additional seven studies since the previous version of this review. All but one study that compared NMES to resistance training compared a programme of NMES to no treatment or placebo NMES. Most studies were conducted in a single centre and had a risk of bias arising from a lack of participant or assessor blinding and small study size. The quality of the evidence using GRADE comparing NMES to control was low for quadriceps muscle strength, moderate for occurrence of adverse events, and very low to low for all other secondary outcomes. We downgraded the quality of evidence ratings predominantly due to inconsistency among study findings and imprecision regarding estimates of effect. The included studies reported no serious adverse events and a low incidence of muscle soreness following NMES.NMES led to a statistically significant improvement in quadriceps muscle strength as compared to the control (12 studies; 781 participants; SMD 0.53, 95% confidence interval (CI) 0.19 to 0.87), equating to a difference of approximately 1.1 kg. An increase in muscle mass was also observed following NMES, though the observable effect appeared dependent on the assessment modality used (eight studies, 314 participants). Across tests of exercise performance, mean differences compared to control were statistically significant for the 6-minute walk test (seven studies; 317 participants; 35 m, 95% CI 14 to 56), but not for the incremental shuttle walk test (three studies; 434 participants; 9 m, 95% CI -35 to 52), endurance shuttle walk test (four studies; 452 participants; 64 m, 95% CI -18 to 146), or for cardiopulmonary exercise testing with cycle ergometry (six studies; 141 participants; 45 mL/minute, 95% CI -7 to 97). Limited data were available for other secondary outcomes, and we could not determine the most beneficial type of NMES programme.

AUTHORS' CONCLUSIONS

The overall conclusions have not changed from the last publication of this review, although we have included more data, new analyses, and an assessment of the quality of the evidence using the GRADE approach. NMES may be an effective treatment for muscle weakness in adults with advanced progressive disease, and could be considered as an exercise treatment for use within rehabilitation programmes. Further research is very likely to have an important impact on our confidence in the estimate of effect and may change the estimate. We recommend further research to understand the role of NMES as a component of, and in relation to, existing rehabilitation approaches. For example, studies may consider examining NMES as an adjuvant treatment to enhance the strengthening effect of programmes, or support patients with muscle weakness who have difficulty engaging with existing services.

Local Muscle Metabolic Demand Induced by Neuromuscular Electrical Stimulation and Voluntary Contractions at Different Force Levels: A NIRS Study

Functional Muscle metabolic demand during contractions evoked by neuromuscular electrical stimulation (NMES) has been consistently documented to be greater than voluntary contractions (VOL) at the same force level (10-50% maximal voluntary contraction-MVC). However, we have shown using a near-infrared spectroscopy (NIRS) technique that local muscle metabolic demand is similar between NMES and VOL performed at MVC levels, thus controversy exists. This study therefore compared biceps brachii muscle metabolic demand (tissue oxygenation index-TOI and total hemoglobin volume-tHb) during a 10s isometric contraction of the elbow flexors between NMES (stimulation frequency of 30Hz and current level to evoke 30% MVC) and VOL at 30% MVC (VOL-30%MVC) and MVC (VOL-MVC) level in 8 healthy men (23-33-y). Greater changes in TOI and tHb induced by NMES than VOL-30%MVC confirm previous studies of a greater local metabolic demand for NMES than VOL at the same force level. The same TOI and tHb changes for NMES and VOL-MVC suggest that local muscle metabolic demand and intramuscular pressure were similar between conditions. In conclusion, these findings indicate that NMES induce a similar local muscle metabolic demand as that of maximal VOL.

Electrical stimulation influences chronic intermittent hypoxia-hypercapnia induction of muscle fibre transformation by regulating the microRNA/Sox6 pathway

Chronic obstructive pulmonary disease can cause muscle fibre transformation due to chronic intermittent hypoxia-hypercapnia (CIHH). Studies have shown that high expression of Sox6 in muscle could suppress type-I fibres through downregulating the PPARβ (peroxisome proliferator-activated receptor β)/ERRγ (oestrogen-related receptor γ)/microRNA pathway. However, whether this pathway is involved in CIHH-induced muscle fibre transformation is unknown. Electrical stimulation (ES) is an effective approach to ameliorate muscle dysfunction. Here, we explored the effects of ES on CIHH-induced muscle fibre transformation and the microRNA/Sox6 pathway. After CIHH exposure, both the soleus (SOL) and gastrocnemius (GC) muscles showed decreased type-I fibres. The PPARβ/ERRγ/mir-499&208b (PEM, for GC) and PPARβ/mir-499&208b (PM, for SOL) signalling cascades were suppressed, followed by elevated Sox6 expression. Low frequency electrical stimulation (LFES) activated the PEM/PM pathway and enhanced type-I fibre numbers through suppressing Sox6 in SOL and GC. High frequency electrical stimulation (HFES) promoted type-I fibre expression through activating the PEM pathway in GC. Although PPARβ expression and type-I fibres were suppressed in SOL after HFES, no significant change was found in mir-499&208b/Sox6 expression. These results suggest that the microRNA/Sox6 pathway is disturbed after CIHH. Both low and high frequency electrical stimulations induce muscle fibre transformation partly through regulating the microRNA/Sox6 pathway.

Effects of Constant and Doublet Frequency Electrical Stimulation Patterns on Force Production of Knee Extensor Muscles

This study compared knee extensors’ neuromuscular fatigue in response to two 30-minute stimulation patterns: constant frequency train (CFT) and doublet frequency train (DFT). Fifteen men underwent two separate sessions corresponding to each pattern. Measurements included torque evoked by each contraction and maximal voluntary contractions (MVC) measured before and immediately after the stimulation sessions. In addition, activation level and torque evoked during doublets (Pd) and tetanic contractions at 80-Hz (P80) and 20-Hz (P20) were determined in six subjects. Results indicated greater mean torque during the DFT stimulation session as compared with CFT. But, no difference was obtained between the two stimulation patterns for MVC and evoked torque decreases. Measurements conducted in the subgroup depicted a significant reduction of Pd, P20 and P80. Statistical analyses also revealed bigger P20 immediate reductions after CFT than after DFT. We concluded that DFT could be a useful stimulation pattern to produce and maintain greater force with quite similar fatigue than CFT.

Changes in structural and metabolic muscle characteristics following exercise-based interventions in patients with COPD: a systematic review

Patients with COPD suffer from lower-limb muscle dysfunction characterized by lower muscle oxidative capacity and muscle mass. Exercise-based training is expected to attenuate lower-limb intramuscular characteristics, but a detailed systematic approach to review the available evidence has not been performed yet. PUBMED and PEDro databases were searched. Twenty-five studies that implemented an exercise-based training program (aerobic and/or resistance training, high intensity interval training, electrical or magnetic stimulation) and reported muscle biopsy data of patients with COPD were critically appraised. The coverage of results includes changes in muscle structure, muscle protein turnover regulation, mitochondrial enzyme activity, oxidative and nitrosative stress, and inflammation after exercise-based training interventions. Study design and training modalities varied among studies, which partly explains the observed heterogeneous response in muscle characteristics. Gaps in the current knowledge are identified and recommendations for future research are made to enhance our knowledge on exercise training effects in patients with COPD.

Electrical Stimulation Improves Rat Muscle Dysfunction Caused by Chronic Intermittent Hypoxia-Hypercapnia via Regulation of miRNA-Related Signaling Pathways

Skeletal muscle dysfunction in chronic obstructive pulmonary disease (COPD) patients is common. Neuromuscular Electrical Stimulation (NMES) is a powerful exercise training that may relieve muscle dysfunction in COPD. This study investigated whether electrical stimulation may have atypical adaptations via activation of miRNA related pathways in counteracting COPD muscle dysfunction. Forty-eight male Sprague-Dawley rats were randomly assigned to 3 groups. With the exception of the rats in the control group, the experimental rats were exposed to chronic intermittent hypoxia-hypercapnia (CIHH) (9∼11%O₂,5.5∼6.5%CO₂) for 2 or 4 weeks. Electrical stimulation was performed immediately after each CIHH session. Following assessment of the running capacity, biopsy samples were obtained from the gastrocnemius of the rats. The miR-1, miR-133a and miR-133b levels were measured, as well as their related proteins: phosphorylation of Akt (p-AKT), PGC-1alpha (PGC-1α), histone deacetylase 4 (HDAC4) and serum response factor (SRF). Myosin heavy chainⅡa (MHCⅡa) and myosin heavy chainⅡb (MHCⅡb) were also measured to assess fiber type changes. After 2 weeks, compared with the controls, only miR-1 and miR-133a were significantly increased (p<0.05) in the exposure group. After 4 weeks, the exposure group exhibited a decreased running distance (p = 0.054) and MHCⅡa-to-MHCⅡb shift (p<0.05). PGC-1α (p = 0.051), nuclear HDAC4 (p = 0.058), HDAC4, p-AKT, PGC-1α and SRF was also significantly decreased (p<0.05). In contrast, miR-1 and miR-133a were significantly increased (p<0.05). Four weeks of electrical stimulation can partly reversed those changes, and miR-133b exhibited a transient increase after 2 weeks electrical stimulation. Our study indicate miRNAs may have roles in the response of CIHH-impaired muscle to changes during electrical stimulation.

Reproducibility of electromyographic and mechanical parameters of the triceps surae during submaximal and maximal plantar flexions

INTRODUCTION

Neuromuscular parameters must be reproducible to examine neuromuscular adaptations in interventional and clinical studies. The reproducibility of neuromuscular parameters for the soleus (SOL), lateral gastrocnemius (LG), and medial gastrocnemius (MG) was assessed over a period of 2 weeks.

METHODS

Thirteen subjects (27.4 years, 69.5 kg) were tested for numerous electromyographic (e.g., voluntary and electrical evoked EMG) and mechanical (e.g., voluntary activation level) parameters in 3 test sessions.

RESULTS

The majority of the data (28 of 34) revealed moderate and substantial reproducibility. Hmax20% /Mmax20% and Vsup /Msup were less reproducible in LG than in MG and SOL. Muscle activity and M-waves did not differ between muscles. The ICC for the mechanical data was >0.79.

CONCLUSIONS

The H-reflex during voluntary contraction of the LG should be considered with caution. Mechanical data on muscle activation level are reproducible. The reproducibility of neuromuscular parameters is sufficient for interventional studies.

Neuromuscular Electrical Stimulation for Motor Restoration in Hemiplegia

This article reviews the most common therapeutic and neuroprosthetic applications of neuromuscular electrical stimulation (NMES) for upper and lower extremity stroke rehabilitation. Fundamental NMES principles and purposes in stroke rehabilitation are explained. NMES modalities used for upper and lower limb rehabilitation are described, and efficacy studies are summarized. The evidence for peripheral and central mechanisms of action is also summarized.

Neuromuscular electrical stimulation leads to physiological gains enhancing postural balance in the pre-frail elderly

Physiological aging leads to a progressive weakening of muscles and tendons, thereby disturbing the ability to control postural balance and consequently increasing exposure to the risks of falls. Here, we introduce a simple and easy-to-use neuromuscular electrical stimulation (NMES) training paradigm designed to alleviate the postural control deficit in the elderly, the first hallmarks of which present as functional impairment. Nine pre-frail older women living in a long-term care facility performed 4 weeks of NMES training on their plantarflexor muscles, and seven nontrained, non-frail older women living at home participated in this study as controls. Participants were asked to perform maximal voluntary contractions (MVC) during isometric plantarflexion in a lying position. Musculo-tendinous (MT) stiffness was assessed before and after the NMES training by measuring the displacement of the MT junction and related tendon force during MVC. In a standing position, the limit of stability (LoS) performance was determined through the maximal forward displacement of the center of foot pressure, and related postural sway parameters were computed around the LoS time gap, a high force requiring task. The NMES training induced an increase in MVC, MT stiffness, and LoS. It significantly changed the dynamics of postural balance as a function of the tendon property changes. The study outcomes, together with a multivariate analysis of investigated variables, highlighted the benefits of NMES as a potential tool in combating neuromuscular weakening in the elderly. The presented training-based strategy is valuable in alleviating some of the adverse functional consequences of aging by directly acting on intrinsic biomechanical and muscular properties whose improvements are immediately transferable into a functional context.

Effects of Increasing Neuromuscular Electrical Stimulation Current Intensity on Cortical Sensorimotor Network Activation: A Time Domain fNIRS Study

Neuroimaging studies have shown neuromuscular electrical stimulation (NMES)-evoked movements activate regions of the cortical sensorimotor network, including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), and secondary somatosensory area (S2), as well as regions of the prefrontal cortex (PFC) known to be involved in pain processing. The aim of this study, on nine healthy subjects, was to compare the cortical network activation profile and pain ratings during NMES of the right forearm wrist extensor muscles at increasing current intensities up to and slightly over the individual maximal tolerated intensity (MTI), and with reference to voluntary (VOL) wrist extension movements. By exploiting the capability of the multi-channel time domain functional near-infrared spectroscopy technique to relate depth information to the photon time-of-flight, the cortical and superficial oxygenated (O₂Hb) and deoxygenated (HHb) hemoglobin concentrations were estimated. The O₂Hb and HHb maps obtained using the General Linear Model (NIRS-SPM) analysis method, showed that the VOL and NMES-evoked movements significantly increased activation (i.e., increase in O₂Hb and corresponding decrease in HHb) in the cortical layer of the contralateral sensorimotor network (SMC, PMC/SMA, and S2). However, the level and area of contralateral sensorimotor network (including PFC) activation was significantly greater for NMES than VOL. Furthermore, there was greater bilateral sensorimotor network activation with the high NMES current intensities which corresponded with increased pain ratings. In conclusion, our findings suggest that greater bilateral sensorimotor network activation profile with high NMES current intensities could be in part attributable to increased attentional/pain processing and to increased bilateral sensorimotor integration in these cortical regions.

The role of alterations in mitochondrial dynamics and PGC-1α over-expression in fast muscle atrophy following hindlimb unloading

KEY POINTS

Skeletal muscle atrophy occurs as a result of disuse. Although several studies have established that a decrease in protein synthesis and increase in protein degradation lead to muscle atrophy, little is known about the triggers underlying such processes. A growing body of evidence challenges oxidative stress as a trigger of disuse atrophy; furthermore, it is also becoming evident that mitochondrial dysfunction may play a causative role in determining muscle atrophy. Mitochondrial fusion and fission have emerged as important processes that govern mitochondrial function and PGC-1α may regulate fusion/fission events. Although most studies on mice have focused on the anti-gravitary slow soleus muscle as it is preferentially affected by disuse atrophy, several fast muscles (including gastrocnemius) go through a significant loss of mass following unloading. Here we found that in fast muscles an early down-regulation of pro-fusion proteins, through concomitant AMP-activated protein kinase (AMPK) activation, can activate catabolic systems, and ultimately cause muscle mass loss in disuse. Elevated muscle PGC-1α completely preserves muscle mass by preventing the fall in pro-fusion protein expression, AMPK and catabolic system activation, suggesting that compounds inducing PGC-1α expression could be useful to treat and prevent muscle atrophy.

ABSTRACT

The mechanisms triggering disuse muscle atrophy remain of debate. It is becoming evident that mitochondrial dysfunction may regulate pathways controlling muscle mass. We have recently shown that mitochondrial dysfunction plays a major role in disuse atrophy of soleus, a slow, oxidative muscle. Here we tested the hypothesis that hindlimb unloading-induced atrophy could be due to mitochondrial dysfunction in fast muscles too, notwithstanding their much lower mitochondrial content. Gastrocnemius displayed atrophy following both 3 and 7 days of unloading. SOD1 and catalase up-regulation, no H2 O2 accumulation and no increase of protein carbonylation suggest the antioxidant defence system efficiently reacted to redox imbalance in the early phases of disuse. A defective mitochondrial fusion (Mfn1, Mfn2 and OPA1 down-regulation) occurred together with an impairment of OXPHOS capacity. Furthermore, at 3 days of unloading higher acetyl-CoA carboxylase (ACC) phosphorylation was found, suggesting AMP-activated protein kinase (AMPK) pathway activation. To test the role of mitochondrial alterations we used Tg-mice overexpressing PGC-1α because of the known effect of PGC-1α on stimulation of Mfn2 expression. PGC-α overexpression was sufficient to prevent (i) the decrease of pro-fusion proteins (Mfn1, Mfn2 and OPA1), (ii) activation of the AMPK pathway, (iii) the inducible expression of MuRF1 and atrogin1 and of authopagic factors, and (iv) any muscle mass loss in response to disuse. As the effects of increased PGC-1α activity were sustained throughout disuse, compounds inducing PGC-1α expression could be useful to treat and prevent muscle atrophy also in fast muscles.

Metabolic load during strength training or NMES in individuals with COPD: results from the DICES trial

Background

Strength training and neuromuscular electrical stimulation (NMES) are effective training modalities for improving muscle function, exercise performance and health status in individuals with COPD. The aim of the present study was to analyze the metabolic load of these training modalities at baseline, half-way, and at the end of an eight-week interdisciplinary pulmonary rehabilitation program in a subgroup of individuals with COPD of the DICES trial.

Methods

Of 24 individuals with COPD (FEV₁: 34 ± 2% predicted, men: 58%, age: 66 (61–68) years), peak oxygen uptake (VO₂), peak minute ventilation (V_E), heart rate, oxygen saturation and symptom scores were assessed during HF-NMES (75 Hz), LF-NMES (15 Hz) and strength training at three moments during their pulmonary rehabilitation program.

Results

Intervention-related peak VO₂ did not change over time during HF-NMES, LF-NMES or strength training. Intervention-related peak V_E did not change over time during strength training or LF-NMES and increased slightly, but significantly over time during HF-NMES. Peak VO₂ and V_E were significantly higher during strength training compared to HF-NMES or LF-NMES. Oxygen saturation significantly decreased after the first measurements during HF-NMES and strength training group to baseline, while no significant changes in oxygen saturation were observed during the other measurements. Heart rate significantly increased compared to baseline in all groups at all moments and was significantly higher after strength training compared to HF-NMES or LF-NMES. Median end scores (points) for dyspnea, fatigue and muscle pain ranged from 1 to 3, from 0.5 to 2 and from 0 to 6 after HF-NMES, from 2 to 3, from 2 to 5 and from 0 to 9 after LF-NMES and from 2 to 5, from 1.5 to 4 and from 0 to 28 after strength training respectively.

Conclusions

To conclude, the metabolic load and symptom scores remain acceptable low over time with increasing training loads during HF-NMES, LF-NMES or strength training.

Trial registration

Trial registration:NTR2322

PGC1-α over-expression prevents metabolic alterations and soleus muscle atrophy in hindlimb unloaded mice

Prolonged skeletal muscle inactivity causes muscle fibre atrophy. Redox imbalance has been considered one of the major triggers of skeletal muscle disuse atrophy, but whether redox imbalance is actually the major cause or simply a consequence of muscle disuse remains of debate. Here we hypothesized that a metabolic stress mediated by PGC-1α down-regulation plays a major role in disuse atrophy. First we studied the adaptations of soleus to mice hindlimb unloading (HU) in the early phase of disuse (3 and 7 days of HU) with and without antioxidant treatment (trolox). HU caused a reduction in cross-sectional area, redox status alteration (NRF2, SOD1 and catalase up-regulation), and induction of the ubiquitin proteasome system (MuRF-1 and atrogin-1 mRNA up-regulation) and autophagy (Beclin1 and p62 mRNA up-regulation). Trolox completely prevented the induction of NRF2, SOD1 and catalase mRNAs, but not atrophy or induction of catabolic systems in unloaded muscles, suggesting that oxidative stress is not a major cause of disuse atrophy. HU mice showed a marked alteration of oxidative metabolism. PGC-1α and mitochondrial complexes were down-regulated and DRP1 was up-regulated. To define the link between mitochondrial dysfunction and disuse muscle atrophy we unloaded mice overexpressing PGC-1α. Transgenic PGC-1α animals did not show metabolic alteration during unloading, preserving muscle size through the reduction of autophagy and proteasome degradation. Our results indicate that mitochondrial dysfunction plays a major role in disuse atrophy and that compounds inducing PGC-1α expression could be useful to treat/prevent muscle atrophy.

Changes in contractile and elastic properties of the triceps surae muscle induced by neuromuscular electrical stimulation training

PURPOSE

Neuromuscular electrical stimulation (NMES) training is known to induce improvement in force production capacities and fibre-type transition. The aim of this study was to determine whether NMES training also leads to changes in the mechanical properties of the human triceps surae (TS) muscle.

METHODS

Fifteen young male subjects performed a training protocol (4 weeks, 18 sessions, 4-5 sessions per week) based on a high-frequency isometric NMES programme of TS muscle. Quick-release test was used to evaluate Musculo-Tendinous (MT) stiffness index (SIMT) as the slope of the linear MT stiffness-torque relationships under submaximal contraction. Sinusoidal perturbations allowed the assessment of musculo-articular stiffness index (SIMA) as well as the calculation of the maximal angular velocity ([Formula: see text]) of TS muscle using an adaptation of Hill's equation.

RESULTS

After NMES training, Maximal Voluntary Contraction under isometric conditions and [Formula: see text] increased significantly by 17.5 and 20.6 %, respectively, while SIMT and SIMA decreased significantly (-12.7 and -9.3 %, respectively).

CONCLUSIONS

These changes in contractile and elastic properties may lead to functional changes of particular interest in sport-related activities as well as in the elderly.

Neuromuscular electrical stimulation prevents muscle disuse atrophy during leg immobilization in humans

AIM

Short periods of muscle disuse, due to illness or injury, result in substantial skeletal muscle atrophy. Recently, we have shown that a single session of neuromuscular electrical stimulation (NMES) increases muscle protein synthesis rates. The aim was to investigate the capacity for daily NMES to attenuate muscle atrophy during short-term muscle disuse.

METHODS

Twenty-four healthy, young (23 ± 1 year) males participated in the present study. Volunteers were subjected to 5 days of one-legged knee immobilization with (NMES; n = 12) or without (CON; n = 12) supervised NMES sessions (40-min sessions, twice daily). Two days prior to and immediately after the immobilization period, CT scans and single-leg one-repetition maximum (1RM) strength tests were performed to assess quadriceps muscle cross-sectional area (CSA) and leg muscle strength respectively. Furthermore, muscle biopsies were taken to assess muscle fibre CSA, satellite cell content and mRNA and protein expression of selected genes.

RESULTS

In CON, immobilization reduced quadriceps CSA by 3.5 ± 0.5% (P < 0.0001) and muscle strength by 9 ± 2% (P < 0.05). In contrast, no significant muscle loss was detected following immobilization in NMES although strength declined by 7 ± 3% (P < 0.05). Muscle MAFbx and MuRF1 mRNA expression increased following immobilization in CON (P < 0.001 and P = 0.07 respectively), whereas levels either declined (P < 0.01) or did not change in NMES, respectively. Immobilization led to an increase in muscle myostatin mRNA expression in CON (P < 0.05), but remained unchanged in NMES.

CONCLUSION

During short-term disuse, NMES represents an effective interventional strategy to prevent the loss of muscle mass, but it does not allow preservation of muscle strength. NMES during disuse may be of important clinical relevance in both health and disease.

Eletroestimulação neuromuscular, exercícios contrarresistência, força muscular, dor e função motora em pacientes com osteoartrite primária de joelho

INTRODUÇÃO: A osteoartrite (OA) do joelho é um processo degenerativo e os sintomas são dor mecânica e períodos de dor inflamatória, rigidez articular e fraqueza muscular. Ela não tem cura. O objetivo do tratamento é aliviar os sinais e sintomas e, quando possível, retardar sua evolução. O fortalecimento muscular é indicado como tratamento da OA. OBJETIVO: Comparar a eficácia da eletroestimulação neuromuscular (EENM) e de exercícios contrarresistência (ECR) no ganho de força extensora de joelho, na diminuição da dor e na recuperação da função motora em pacientes com OA primária do joelho. MATERIAIS E MÉTODOS: Participaram da pesquisa 23 pacientes com diagnóstico de OA primária do joelho, segundo os critérios clínicos e radiológicos do American College of Rheumatology. Eles foram alocados aleatoriamente para um grupo de ECR (n = 9), um grupo de EENM (n = 8) e um grupo controle (n = 6), e foram submetidos aos procedimentos característicos de seu grupo três vezes por semana até completar 24 sessões. Foram avaliadas de forma cega a força extensora de joelho, a dor e a função motora. Foi utilizado o teste MANOVA 3 x 2 com medidas repetidas para P < 0,05. RESULTADOS: Foi encontrada diferença significativa (P < 0.05) somente nas comparações intragrupos para força extensora de joelho no grupo EENM e para dor nos grupos EENM e ECR. CONCLUSÃO: O fortalecimento da musculatura extensora de joelho pode auxiliar na diminuição da dor de pacientes com OA. A EENM, quando aplicada de acordo com o protocolo utilizado neste estudo, pode ser uma terapia interessante para o tratamento da OA do joelho.

Effects of pulse current on endurance exercise and its anti-fatigue properties in the hepatic tissue of trained rats

Fatigue is synonymous with a wide spectrum of familiar physiological conditions, from pathology and general health, to sport and physical exercise. Strenuous, prolonged exercise training causes fatigue. Although several studies have investigated the effects of electrical stimulation frequency on muscle fatigue, the effects of percutaneous pulse current stimulation on fatigue in the hepatic tissue of trained rats is still unclear. In order to find an effective strategy to prevent fatigue or enhance recovery, the effects of pulse current on endurance exercise and its anti-fatigue properties in exercised rats were studied. Rats were subjected to one, three or five weeks of swimming exercise training. After exercise training, rats in the treated group received daily applications of pulse current. All rats were sacrificed after one, three or five weeks of swimming exercise, and the major biochemical indexes were measured in serum and liver. The results demonstrate that pulse current could prolong the exhaustion swimming time, as well as decrease serum ALT, AST and LD levels and liver MDA content. It also elevated serum LDH activity, liver SOD activity and glycogen content. Furthermore, pulse current increased the expression of Bcl-2 and decreased the expression of Bax. Taken together, these results show that pulse current can elevate endurance capacity and facilitate recovery from fatigue.

Metabolic and structural changes in lower-limb skeletal muscle following neuromuscular electrical stimulation: a systematic review

Background

Transcutaneous neuromuscular electrical stimulation (NMES) can be applied as a complementary intervention to regular exercise training programs. A distinction can be made between high-frequency (HF) NMES and low-frequency (LF) NMES. In order to increase understanding of the mechanisms of functional improvements following NMES, the purpose of this study was to systematically review changes in enzyme activity, muscle fiber type composition and muscle fiber size in human lower-limb skeletal muscles following only NMES.

Methods

Trials were collected up to march 2012 and were identified by searching the Medline/PubMed, EMBASE, Cochrane Central Register of Controlled Trials, CINAHL and The Physical Therapy Evidence Database (PEDro) databases and reference lists. 18 trials were reviewed in detail: 8 trials studied changes in enzyme activities, 7 trials studied changes in muscle fiber type composition and 14 trials studied changes in muscle fiber size following NMES.

Results

The methodological quality generally was poor, and the heterogeneity in study design, study population, NMES features and outcome parameters prohibited the use of meta-analysis. Most of the LF-NMES studies reported significant increases in oxidative enzyme activity, while the results concerning changes in muscle fiber composition and muscle size were conflicting. HF-NMES significantly increased muscle size in 50% of the studies.

Conclusion

NMES seems to be a training modality resulting in changes in oxidative enzyme activity, skeletal muscle fiber type and skeletal muscle fiber size. However, considering the small sample sizes, the variance in study populations, the non-randomized controlled study designs, the variance in primary outcomes, and the large heterogeneity in NMES protocols, it is difficult to draw definitive conclusions about the effects of stimulation frequencies on muscular changes.

Proteomic identification of biomarkers of skeletal muscle disorders

Disease-specific biomarkers play a central diagnostic and therapeutic role in muscle pathology. Serum levels of a variety of muscle-derived enzymes are routinely used for the detection of muscle damage in diagnostic procedures, as well as for the monitoring of physical training status in sports medicine. Over the last few years, the systematic application of mass spectrometry-based proteomics for studying skeletal muscle degeneration has greatly expanded the range of muscle biomarkers, including new fiber-associated proteins involved in muscle transformation, muscular atrophy, muscular dystrophy, motor neuron disease, inclusion body myositis, myotonia, hypoxia, diabetes, obesity and sarcopenia of old age. These mass spectrometric studies have clearly established skeletal muscle proteomics as a reliable method for the identification of novel indicators of neuromuscular diseases.

The effect of electrical stimulation on corticospinal excitability is dependent on application duration: a same subject pre-post test design

BACKGROUND

In humans, corticospinal excitability is known to increase following motor electrical stimulation (ES) designed to mimic a voluntary contraction. However, whether the effect is equivalent with different application durations and whether similar effects are apparent for short and long applications is unknown. The aim of this study was to investigate whether the duration of peripheral motor ES influenced its effect on corticospinal excitability.

METHODS

The excitability of the corticomotor pathway to abductor pollicis brevis (APB) was measured in fourteen health subjects using transcranial magnetic stimulation before, immediately after and 10 minutes after three different durations (20-, 40-, 60-min) of motor ES (30Hz, ramped). This intervention was designed to mimic a voluntary contraction in APB. To control for effects of motor ES on the peripheral elements (muscle fibre, membrane, neuromuscular junction), maximum compound muscle actions potentials (M-waves) were also recorded at each time point. Results were analysed using a repeated measures analysis of variance.

RESULTS

Peripheral excitability was reduced following all three motor ES interventions. Conversely, corticospinal excitability was increased immediately following 20- and 40-min applications of motor ES and this increase was maintained at least 20-min following the intervention. A 60-min application of motor ES did not alter corticospinal excitability.

CONCLUSIONS

A 20-min application of motor ES that is designed to mimic voluntary muscle contraction is as effective as that applied for 40-min when the aim of the intervention is to increase corticospinal excitability. Longer motor ES durations of 60-min do not influence corticospinal excitability, possibly as a result of homeostatic plasticity mechanisms.

Sternohyoid and diaphragm muscle form and function during postnatal development in the rat

NEW FINDINGS

What is the central question of this study? Co-ordinated activity of the thoracic pump and pharyngeal dilator muscles is critical for maintaining airway calibre and respiratory homeostasis. Whilst postnatal maturation of the diaphragm has been well characterized, surprisingly little is known about the developmental programme in the airway dilator muscles. What is the main finding and its importance? Developmental increases in force-generating capacity and fatigue in the sternohyoid and diaphragm muscles are attributed to a maturational shift in muscle myosin heavy chain phenotype. This maturation is accelerated in the sternohyoid muscle relative to the diaphragm and may have implications for the control of airway calibre in vivo. The striated muscles of breathing, including the thoracic pump and pharyngeal dilator muscles, play a critical role in maintaining respiratory homeostasis. Whilst postnatal maturation of the diaphragm has been well characterized, surprisingly little is known about the developmental programme in airway dilator muscles given that co-ordinated activity of both sets of muscles is needed for the maintenance of airway calibre and effective pulmonary ventilation. The form and function of sternohyoid and diaphragm muscles from Wistar rat pups [postnatal day (PD) 10, 20 and 30] was determined. Isometric contractile and endurance properties were examined in tissue baths containing Krebs solution at 35°C. Myosin heavy chain (MHC) isoform composition was determined using immunofluorescence. Muscle oxidative and glycolytic capacity was assessed by measuring the activities of succinate dehydrogenase and glycerol-3-phosphate dehydrogenase using semi-quantitative histochemistry. Sternohyoid and diaphragm peak isometric force and fatigue increased significantly with postnatal maturation. Developmental myosin disappeared by PD20, whereas MHC2B areal density increased significantly from PD10 to PD30, emerging earlier and to a much greater extent in the sternohyoid muscle. The numerical density of fibres expressing MHC2X and MHC2B increased significantly during development in the sternohyoid. Diaphragm succinate dehydrogenase activity and sternohyoid glycerol-3-phosphate dehydrogenase activity increased significantly with age. Developmental increases in force-generating capacity and fatigue in the sternohyoid and diaphragm muscles are attributed to a postnatal shift in muscle MHC phenotype. The accelerated maturation of the sternohyoid muscle relative to the diaphragm may have implications for the control of airway calibre in vivo.

Neuromuscular electrical stimulation for muscle weakness in adults with advanced disease

BACKGROUND

Patients with progressive diseases often experience muscle weakness, which impacts adversely on levels of independence and quality of life. In those who are unable or unwilling to undertake traditional forms of exercise, neuromuscular electrical stimulation (NMES) may provide an alternative method of enhancing leg muscle strength. Programmes appear to be well tolerated and have led to improvements in muscle function, exercise capacity and quality of life. However, estimates regarding the effectiveness of NMES from individual studies lack power and precision.

PRIMARY OBJECTIVE

to evaluate the effectiveness of NMES for improving muscle strength in adults with advanced disease.

SECONDARY OBJECTIVE

to examine the acceptability and safety of NMES, and changes in muscle function (strength or endurance), muscle mass, exercise capacity, breathlessness and health-related quality of life.

SEARCH METHODS

Studies were identified from searches of The Cochrane Library, MEDLINE, EMBASE, CINAHL and PsycINFO databases to July 2012, citation searches, conference proceedings and previous systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in adults with advanced chronic obstructive pulmonary disease (COPD), chronic heart failure, cancer or human immunodeficiency virus/acquired immunodeficency syndrome (HIV/AIDS) comparing a programme of NMES as a sole or adjunct intervention to no treatment, placebo NMES or an active control. We imposed no language restriction.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data on study design, participants, interventions and outcomes. We assessed risk of bias using the Cochrane Collaboration's tool. We calculated mean differences (MD) or standardised mean differences (SMD) between intervention and control groups for outcomes with sufficient data; for other outcomes we described findings from individual studies.

MAIN RESULTS

Eleven studies involving a total of 218 participants met the inclusion criteria across COPD, chronic heart failure and thoracic cancer. NMES significantly improved quadriceps strength by a SMD of 0.9 (95% confidence interval (CI) 0.33 to 1.46), equating to approximately 25 Newton metres (Nm) (95% CI 9 to 41). Mean differences across various walking tests, favouring NMES, were 40 m (95% CI -4 to 84) for the six-minute walk test, 69 m (95% CI 19 to 119) for the incremental shuttle walk test and 160 m (95% CI 34 to 287) for the endurance shuttle walk test. Limited evidence was available for the assessment of other secondary outcomes.

AUTHORS' CONCLUSIONS

NMES appears an effective means of improving muscle weakness in adults with progressive diseases such as COPD, chronic heart failure and cancer. Further research is required to clarify its place in clinical practice, by determining the optimal parameters for a NMES programme, the patients most likely to benefit, and its impact on morbidity and service use.

Neuromuscular stimulation of quadriceps in patients hospitalised during an exacerbation of COPD: a comparison of low (35 Hz) and high (50 Hz) frequencies

BACKGROUND

Neuromuscular electrical stimulation (NMES) has shown to improve skeletal muscle strength and exercise capacity in stable patients with chronic obstructive pulmonary disease (COPD). Variations in NMES protocols are considerable. We aimed to compare changes in muscle strength after high-frequency and low-frequency NMES in patients admitted to hospital with an acute exacerbation of COPD.

METHODS

Patients were referred for inpatient (IP) rehabilitation during hospitalisation for an acute worsening of their COPD. They received 30-minute daily NMES to both quadriceps at a frequency of 35 or 50 Hz. NMES intensity was titrated to patients' tolerance. Isometric quadriceps muscle strength and endurance walking (ESWT) time were measured at baseline and on hospital discharge.

RESULTS

A total of 10 patients in each treatment group underwent NMES during hospitalisation (mean [SD] age 68.0 [±7.4] years, FEV1 0.99 L [±0.58], FEV1/FVC 47% [± 27%], MRC 5 [IQR ±1]). There were no significant differences in baseline characteristics between groups. Muscle strength (legs combined) increased in both groups regardless of the NMES frequency used (35 Hz--3.8 ± 4.9; 50 Hz--3.4 ± 5.5 kg). This was only significant within the 35 Hz group. The change in ESWT also showed a trend to increase in both groups (35 Hz--109 ± 92.7; 50 Hz--145.6 ± 94.7). There was no significant difference between groups for either outcome.

CONCLUSION

NMES is a feasible intervention to improve muscle strength in a cohort of patients admitted with an exacerbation of COPD. The response appears to be independent of the frequency used and both were well-tolerated.

Lack of functional effects of neuromuscular electrical stimulation on skeletal muscle oxidative metabolism in healthy humans

A recent study has demonstrated that neuromuscular electrical stimulation (NMES) determines, in vitro, a fast-to-slow shift in the metabolic profile of muscle fibers. The aim of the present study was to evaluate if, in the same subjects, these changes would translate, in vivo, into an enhanced skeletal muscle oxidative metabolism. Seven young men were tested (cycle ergometer) during incremental exercises up to voluntary exhaustion and moderate and heavy constant-load exercises (CLE). Measurements were carried out before and after an 8-wk training program by isometric bilateral NMES (quadriceps muscles), which induced an ∼25% increase in maximal isometric force. Breath-by-breath pulmonary O2 uptake (V̇o2) and vastus lateralis oxygenation indexes (by near-infrared spectroscopy) were determined. Skeletal muscle fractional O2 extraction was estimated by near-infrared spectroscopy on the basis of changes in concentration of deoxygenated hemoglobin + myoglobin. Values obtained at exhaustion were considered “peak” values. The following functional evaluation variables were unaffected by NMES: peak V̇o2; gas exchange threshold; the V̇o2 vs. work rate relationship (O2 cost of cycling); changes in concentration of deoxygenated hemoglobin + myoglobin vs. work rate relationship (related to the matching between O2 delivery and V̇o2); peak fractional O2 extraction; V̇o2 kinetics (during moderate and heavy CLE) and the amplitude of its slow component (during heavy CLE). Thus NMES did not affect several variables of functional evaluation of skeletal muscle oxidative metabolism. Muscle hypertrophy induced by NMES could impair peripheral O2 diffusion, possibly counterbalancing, in vivo, the fast-to-slow phenotypic changes that were observed in vitro, in a previous work, in the same subjects of the present study.

Tongue anatomy and physiology, the scientific basis for a novel targeted neurostimulation system designed for the treatment of obstructive sleep apnea

INTRODUCTION

 Obstructive sleep apnea (OSA) is a chronic condition that affects millions adults. The effective standard treatment is positive airway pressure (PAP). However, approximately half of the patients that are prescribed PAP are unable or unwilling to comply with this therapy. Untreated OSA ultimately leads to very serious comorbidities. An alternative therapy for this patient population, therefore, is desirable. Hypoglossal nerve (HGN) stimulation is under investigation by multiple groups as a possible alternative therapy for OSA.

OBJECTIVE

To understand the underlying mechanisms of actions related to HGN stimulation, and the implication of this knowledge for specifying and designing a neurostimulation system for the treatment of OSA.

RESULTS

 Loss of lingual and pharyngeal tone within a narrow airway is the primary mechanism for OSA. Posterior and anterior tongues are different in their anatomy and physiology. Muscle fibers in the posterior tongue are predominantly fatigue resistant that are responsible for the long sustained tonic activities required for maintaining the tongue's position and preventing its mass from falling into the retroglossal airway. The human tongue is a muscular hydrostat and hence would benefit from a sophisticated HGN stimulation system that is capable of achieving a concerted spatio-temporal interplay of multiple lingual muscles, including retrusors.

CONCLUSION

 Targeted neurostimulation of the proximal HGN presents as a viable system approach that is far more versatile and physiologic and quite different than prior systems.

The time course of the adaptations of human muscle proteome to bed rest and the underlying mechanisms

In order to get a comprehensive picture of the complex adaptations of human skeletal muscle to disuse and further the understanding of the underlying mechanisms, we participated in two bed rest campaigns, one lasting 35 days and one 24 days. In the first bed rest (BR) campaign, myofibrillar proteins, metabolic enzymes and antioxidant defence systems were found to be down-regulated both post-8 days and post-35 days BR by proteomic analysis of vastus lateralis muscle samples from nine subjects. Such profound alterations occurred early (post-8 days BR), before disuse atrophy developed, and persisted through BR (post-35 days BR). To understand the mechanisms underlying the protein adaptations observed, muscle biopsies from the second bed rest campaign (nine subjects) were used to evaluate the adaptations of master controllers of the balance between muscle protein breakdown and muscle protein synthesis (MuRF-1 and atrogin-1; Akt and p70S6K), of autophagy (Beclin-1, p62, LC3, bnip3, cathepsin-L), of expression of antioxidant defence systems (NRF2) and of energy metabolism (PGC-1α, SREBP-1, AMPK). The results indicate that: (i) redox imbalance and remodelling of muscle proteome occur early and persist through BR; (ii) impaired energy metabolism is an early and persistent phenomenon comprising both the oxidative and glycolytic one; (iii) although both major catabolic systems, ubiquitin proteasome and autophagy, could contribute to the progression of atrophy late into BR, a decreased protein synthesis cannot be ruled out; (iv) a decreased PGC-1α, with the concurrence of SREBP-1 up-regulation, is a likely trigger of metabolic impairment, whereas the AMPK pathway is unaltered.

Motor unit recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly: quadriceps femoris

Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and both can generate contractions through peripheral and central pathways. Generating contractions through peripheral pathways is associated with a nonphysiological motor unit recruitment order, which may limit the efficacy of NMES rehabilitation. Presently, we compared recruitment through peripheral and central pathways for contractions of the knee extensors evoked by NMES applied over the femoral nerve vs. the quadriceps muscle. NMES was delivered to evoke 10 and 20% of maximum voluntary isometric contraction torque 2–3 s into the NMES (time1) in two patterns: 1) constant frequency (15 Hz for 8 s); and 2) step frequency (15–100-15 Hz and 25–100-25 Hz for 3–2-3 s, respectively). Torque and electromyographic activity recorded from vastus lateralis and medialis were quantified at the beginning (time1) and end (time2; 6–7 s into the NMES) of each pattern. M-waves (peripheral pathway), H-reflexes, and asynchronous activity (central pathways) during NMES were quantified. Torque did not differ regardless of NMES location, pattern, or time. For both muscles, M-waves were ∼7–10 times smaller and H-reflexes ∼8–9 times larger during NMES over the nerve compared with over the muscle. However, unlike muscles studied previously, neither torque nor activity through central pathways were augmented following 100 Hz NMES, nor was any asynchronous activity evoked during NMES at either location. The coefficient of variation was also quantified at time2to determine the consistency of each dependent measure between three consecutive contractions. Torque, M-waves, and H-reflexes were most variable during NMES over the nerve. In summary, NMES over the nerve produced contractions with the greatest recruitment through central pathways; however, considering some of the limitations of NMES over the femoral nerve, it may be considered a good complement to, as opposed to a replacement for, NMES over the quadriceps muscle for maintaining muscle quality and reducing contraction fatigue during NMES rehabilitation.

Aerobic neuromuscular electrical stimulation--an emerging technology to improve haemoglobin A1c in type 2 diabetes mellitus: results of a pilot study

OBJECTIVES

A new generation of neuromuscular electrical stimulation (NMES) devices can exercise aerobically at equivalent rates to voluntary exercise. Many with type 2 diabetes cannot or will not exercise sufficiently. The objective of this pilot investigation was to see (1) if it was an acceptable training modality for men with type 2 diabetes mellitus and (2) to assess effects on haemoglobin A1c levels.

DESIGN, SETTING, PARTICIPANTS AND INTERVENTION

A case series of eight men with type 2 diabetes mellitus (aged 53±8; body mass index 32±5 5 kg/m(2)) trained with the NMES system for 1 h 6 times weekly for 8 weeks, unsupervised, at home. There were no other medication or lifestyle interventions. The aerobic NMES exercise system delivers a repeating set of four complex staggered pulses at high intensities (typically 100 mA+) through an array of eight thigh electrodes.

OUTCOME MEASURES

The primary outcome measures were changes in haemoglobin A1c and the responses in a questionnaire on participants' perceptions of the system. Body mass and composition were also measured before and after the NMES intervention period.

RESULTS

All participants could use the system at a level that left them breathless and sweaty and with a heart rate over 120 beats per minute. Haemoglobin A1c levels improved by 0.8±0.7% from 7.4±1.3% (mean ± SD) to 6.6±1.0% (p=0.01). All participants considered the system suitable for people with diabetes, would recommend it and would continue to use it twice a week 'to maintain improvements'.

CONCLUSIONS

These results suggest that aerobic NMES may be acceptable and have a beneficial effect on haemoglobin A1c of some men with diabetes. The treatment may be of particular benefit in those who will not or cannot do adequate amounts of voluntary exercise. A randomised control trial is required for conclusive efficacy data.

Comparison of single- and two-channel neuromuscular electrical stimulation sites for enhancing venous return

Neuromuscular electrical stimulation (NMES) has previously been used to activate the musculature of the lower leg and increase venous return to the heart. However, there is little evidence to suggest the superiority of one particular stimulation site over another. In this paper, we aim to reveal the optimal stimulation site on the lower leg in a group of healthy adults. Doppler ultrasound measurements of venous blood volume expelled and peak venous velocity in response to various single and two-channel applications of NMES were taken for each subject. We found that soleus NMES is the most effective single-channel stimulation method, capable of expelling 58.3% of the blood achieved during a voluntary contraction, alternatively soleus plus tibialis posterior stimulation is capable of expelling 76.5%. Based on these and other factors we suggest that the soleus and soleus plus tibialis posterior are the most effective NMES sites for improving venous return.

Electrical muscle stimulation: an effective form of exercise and early mobilization to preserve muscle strength in critically ill patients

Purpose. This is a secondary analysis of previously published data to investigate the effects of electrical muscle stimulation (EMS) on strength of various muscle groups in critically ill patients. Methods. One hundred forty-two consecutive patients, with APACHE II score ≥ 13, were randomly assigned to the EMS or the control group. EMS sessions were applied daily on vastus lateralis, vastus medialis, and peroneus longus of both lower extremities. Various muscle groups were evaluated with the Medical Research Council (MRC) scale for muscle strength. Handgrip strength assessment was also employed. Results. Twenty four patients in the EMS group and 28 patients in the control group were finally evaluated. EMS patients achieved higher MRC scores than controls (P ≤ 0.05) in wrist flexion, hip flexion, knee extension, and ankle dorsiflexion. Collectively, the EMS group performed higher (P < 0.01) in the legs and overall. Handgrip strength correlated (P ≤ 0.01) with the upper and lower extremities' muscle strength and the overall MRC scores. Conclusions. EMS has beneficial effects on the strength of critically ill patients mainly affecting muscle groups stimulated, while it may also affect muscle groups not involved presenting itself as a potential effective means of muscle strength preservation and early mobilization in this patient population.

Therapeutic modalities--an updated review for the hand surgeon

The number of therapeutic modalities available to the hand surgeon has greatly increased over the past several decades. A field once predicated only on heat, massage, and cold therapy now uses electrical stimulators, ultrasound, biofeedback, iontophoresis, phonophoresis, mirror therapy, lasers, and a number of other modalities. With this expansion in choices, there has been a concurrent effort to better define which modalities are truly effective. In this review, we aim to characterize the commonly used modalities and provide the evidence available that supports their continued use.

Functional and muscular effects of neuromuscular electrical stimulation in patients with severe COPD: a randomized clinical trial

BACKGROUND

The mechanisms through which neuromuscular electrical stimulation (NMES) training may improve limb muscle function and exercise tolerance in COPD are poorly understood. We investigated the functional and muscular effects of NMES in advanced COPD.

METHODS

Twenty of 22 patients with COPD were randomly assigned to NMES (n = 12) or sham (n = 8) training in a double-blind controlled study. NMES was performed on quadriceps and calf muscles, at home, 5 days per week for 6 weeks. Quadriceps and calf muscle cross-sectional area (CSA), quadriceps force and endurance, and the shuttle-walking distance with cardiorespiratory measurements were assessed before and after training. Quadriceps biopsy specimens were obtained to explore the insulin-like growth factor-1/AKT signaling pathway (70-kDa ribosomal S6 kinase [p70S6K] , atrogin-1).

RESULTS

NMES training improved muscle CSA (P < .05), force, and endurance (P < .03) when compared with sham training. Phosphorylated p70S6K levels (anabolism) were increased after NMES as compared with sham (P = .03), whereas atrogin-1 levels (catabolism) were reduced (P = .01). Changes in quadriceps strength and ventilation during walking contributed independently to variations in walking distance after training (r = 0.77, P < .001). Gains in walking distance were related to the ability to tolerate increasing current intensities during training (r = 0.95, P < .001).

CONCLUSIONS

In patients with severe COPD, NMES improved muscle CSA. This was associated with a more favorable muscle anabolic to catabolic balance. Improvement in walking distance after NMES training was associated with gains in muscle strength, reduced ventilation during walking, and the ability to tolerate higher stimulation intensity.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00874965; URL: www.clinicaltrials.gov.

Neural adaptations to electrical stimulation strength training

This review provides evidence for the hypothesis that electrostimulation strength training (EST) increases the force of a maximal voluntary contraction (MVC) through neural adaptations in healthy skeletal muscle. Although electrical stimulation and voluntary effort activate muscle differently, there is substantial evidence to suggest that EST modifies the excitability of specific neural paths and such adaptations contribute to the increases in MVC force. Similar to strength training with voluntary contractions, EST increases MVC force after only a few sessions with some changes in muscle biochemistry but without overt muscle hypertrophy. There is some mixed evidence for spinal neural adaptations in the form of an increase in the amplitude of the interpolated twitch and in the amplitude of the volitional wave, with less evidence for changes in spinal excitability. Cross-sectional and exercise studies also suggest that the barrage of sensory and nociceptive inputs acts at the cortical level and can modify the motor cortical output and interhemispheric paths. The data suggest that neural adaptations mediate initial increases in MVC force after short-term EST.