Background
Individual studies suggest that neuromuscular electrical stimulation, or NMES, may help improve the muscle weakness that people often experience as a consequence of a progressive disease. NMES uses a lightweight stimulator unit and skin electrodes to produce a controlled and comfortable muscle contraction. Being a passive form of exercise, NMES allows patients to exercise their leg muscles at home whilst seated. This may be particularly helpful for people who are unable to take part in more strenuous forms of exercise, for example because of shortness of breath or fatigue.
Key results
In this review update we considered 18 clinical studies comparing NMES to either no exercise, placebo NMES, or weight training in groups of people with advanced chronic respiratory disease, chronic heart failure, and/or cancer of the lungs. NMES appeared to be more effective than the control conditions at improving thigh muscle strength. We also observed a positive effect on this outcome when precise measures were used to assess muscle bulk. The evidence for an effect of NMES on ability to exercise was inconclusive. Further research is required to understand how NMES can be used within broader rehabilitation approaches that combine exercise with education and behaviours to reduce the impact of muscle weakness on daily life, for example becoming more physically active.
Quality of the evidence
We rated the quality of the evidence from studies using four levels: very low, low, moderate, or high. Very low-quality evidence means that we are very uncertain about the results. High-quality evidence means that we are very confident in the results. Overall, the quality of the evidence was low for the effect on thigh muscle strength and very low to moderate for the effects on other outcomes. There were problems with the design of some studies; often people taking part or assessors knew if they were receiving or testing NMES. In addition, the results for many outcomes were inconsistent or imprecise.
Implications for practice and research
This review suggests that NMES is a potentially effective treatment for muscle weakness in people with progressive diseases such as cancer, advanced chronic respiratory disease, and chronic heart failure, though the quality of the evidence is low. NMES might be considered for use within rehabilitation programmes. It was not possible to compare the effects of NMES to other forms of exercise, for example weight training, because the majority of studies compared NMES to a control group that received no treatment or a sham treatment. Further research is needed to understand the effect of NMES on the ability to exercise and quality of life.
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.
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.
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.
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.
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.
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.
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.