Abstract
ObjectiveThis study aimed to determine whether kilohertz-frequency alternating current (KFAC) is superior to low-frequency pulsed current (PC) in increasing muscle-evoked torque and lessening discomfort.Data sourcesThe electronic databases PubMed, PEDro, CINAHL, and CENTRAL were searched for related articles, published before August 2017. Furthermore, citation search was performed on the original record using Web of Science.Review methodsRandomized controlled trials, quasi-experimental studies, and within-subject repeated studies evaluating and comparing KFAC and PC treatments were included. The pooled standardized mean differences (SMDs) of KFAC and PC treatments, with 95% confidence intervals (CIs), were calculated using the random effects model.ResultsIn total, 1148 potentially relevant articles were selected, of which 14 articles with within-subject repeated designs (271 participants, mean age: 26.4 years) met the inclusion criteria. KFAC did not significantly increase muscle-evoked torque, compared to PC (pooled SMD: -0.25; 95% CI: -0.53, 0.06; P = 0.120). KFAC had comparable discomfort compared to that experienced using PC (pooled SMD: -0.06; 95% CI: -0.50, 0.38; P = 0.800). These estimates of the effects had a high risk of bias, as assessed using the Downs and Black scale, and were highly heterogeneous studies.ConclusionsThis meta-analysis does not establish that KFAC is superior to PC in increasing muscle-evoked torque and lessening discomfort level. However, no strong conclusion could be drawn because of a high risk of bias and a large amount of heterogeneity. High quality studies comparing the efficacy between PC and KFAC treatments with consideration of potential confounders is warranted to facilitate the development of effective treatment.
Highlights
Neuromuscular electrical stimulation (NMES) is used in the clinical setting of rehabilitation, primarily to enhance muscle strength, in subjects who are unable to perform conventional exercise.[1]
kilohertz-frequency alternating current (KFAC) had comparable discomfort compared to that experienced using pulsed current (PC)
High quality studies comparing the efficacy between PC and KFAC treatments with consideration of potential confounders is warranted to facilitate the development of effective treatment
Summary
Neuromuscular electrical stimulation (NMES) is used in the clinical setting of rehabilitation, primarily to enhance muscle strength, in subjects who are unable to perform conventional exercise.[1]. A large heterogeneity existed among included subjects, approaches to explore the cause of heterogeneity, such as subgroup and meta-regression analyses, were not performed These points are important, because confidence in the effects estimate from meta-analysis depends on the quality of the included studies and analytic process of the meta-analysis,[10] as the former can be evaluated by the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach.[11] It is important to emphasize that the effects estimate comparing KFAC and PC treatments in the previous meta-analysis had wide 95% confidence intervals (CIs),[8] which could change the clinical decision if the true effects estimates are in the upper or lower boundary.[12] Recently, additional relevant articles were reported [13, 14]; precision of effects estimate would be increased by synthesizing all these articles. These updated information would be helpful for clinicians and physical therapists in making and improving evidence-based treatment regimen using NMES for muscle strength
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