Association between Disability and Psychological Factors and Dose of Neuromuscular Electrical Stimulation in Subjects with Rheumatoid Arthritis

Dose-Response Relationship Between Neuromuscular Electrical Stimulation and Muscle Function in People With Rheumatoid Arthritis

BACKGROUND

Neuromuscular electrical stimulation (NMES) is a viable intervention for improving impaired muscle function in individuals with rheumatoid arthritis (RA). However, there is limited evidence about the dose-response relationship between NMES and muscle function in these individuals.

OBJECTIVE

The objectives of this study were to investigate the dose-response relationship between NMES and muscle function in individuals with RA and to establish the minimal NMES training intensity for promoting improvements.

DESIGN

This study was a secondary analysis of data obtained before and after an NMES intervention in a randomized study.

METHODS

The study took place at a research clinic. Only adults diagnosed with RA were included. The intervention consisted of 36 NMES treatment sessions for the quadriceps muscles over 16 weeks. Muscle function was measured before and after the intervention; quadriceps cross-sectional area and muscle quality were assessed using computed tomography, and strength was measured with an isokinetic dynamometer. NMES training intensity was calculated as a percentage by dividing NMES-elicited quadriceps muscle torque by the maximum voluntary isometric contraction. Improvements in muscle function were calculated using paired-sample t tests. The dose-response relationship was determined using curve estimation regression statistics. The minimum NMES training intensity was defined as that sufficient to significantly improve all muscle function measures.

RESULTS

Twenty-four people (48 legs) participated (75% women; mean [SD] age = 58 [8] years; mean body mass index = 32 [7] kg/m2). Quadriceps cross-sectional area, muscle quality, and strength improved after the intervention. Associations between NMES training intensity and muscle quality (r2 = 0.20) and strength (r2 = 0.23) were statistically significant, but that between NMES training intensity and muscle cross-sectional area was not (r2 = 0.02). The minimum NMES training intensity necessary to improve all measures of muscle function ranged from 11% to 20% of the maximum voluntary isometric contraction.

LIMITATIONS

The relatively small sample size was a limitation.

CONCLUSIONS

The minimum NMES training intensity for significant gains in muscle function was ∼15%. Higher NMES intensities may promote better muscle quality and strength in individuals with RA.

Transcutaneous Electrical Stimulation on the Submental Area: The Relations of Biopsychological Factors with Maximum Amplitude Tolerance and Perceived Discomfort Level

Transcutaneous electrical stimulation (TES) is a frequently used adjunctive modality in dysphagia rehabilitation. Stimulating deeper swallowing muscles requires higher TES amplitude. However, TES amplitude is limited by maximum amplitude tolerance (MAT). Previous studies have reported high interindividual variability regarding MAT and perceived discomfort. This variability might be one of the potential reasons of conflicting outcomes in TES-based swallowing studies. MAT and perceived discomfort are influenced by a variety of biopsychological factors. The influence of these factors related to swallow applications is poorly understood. This study explored the relation of biopsychological factors with MAT and perceived discomfort related to TES in the submental area. A convenience sample of thirty community-dwelling older adults between 60 and 70 years of age provided data for this study. Gender, submental adipose tissue thickness, perceptual pain sensitivity, and pain-coping strategies were evaluated for each subject. Subsequently, MAT and perceived discomfort level were determined using TES on the submental area. Relation of different biopsychological variables with MAT and discomfort level was examined using Pearson and Spearman correlation, and Mann-Whitney U test. Results indicated that neither gender nor adipose thickness was related to MAT and perceived discomfort. Among studied pain-coping strategies, catastrophizing was significantly related to MAT(r = - 0.552, p < .002). Distraction was significantly related to perceived discomfort level (r = - 0.561, p < 0.002). Given the negative impact of pain catastrophizing on MAT and the positive impact of distraction on perceiving discomfort, these coping strategies should be considered as amplitude-limiting and discomfort-moderating factors in TES-based dysphagia rehabilitation.

Neuromuscular Electrical Stimulation Compared to Volitional Exercise for Improving Muscle Function in Rheumatoid Arthritis: A Randomized Pilot Study

OBJECTIVE

The aim of this study was to compare the feasibility and effectiveness of neuromuscular electrical stimulation (NMES) with that of high-intensity volitional resistance training for improving muscle structure and function and physical function in patients with rheumatoid arthritis (RA). We also compared pre-intervention and post-intervention values of myocyte characteristics.

METHODS

In this 2-group, single-blind, randomized pilot study, adult patients with RA were assigned to 36 sessions of NMES (n = 31 patients) or volitional training (n = 28 patients) over 16 weeks. Outcome measures included muscle structure and function (quadriceps muscle area, density, and strength), physical function (performance-based and patient-reported), feasibility (increased pain, increased disease activity, attrition, and adherence), and myocyte characteristics (area, proportion of type I or II muscle fibers, and intramyocellular lipid content). Analysis of covariance was used to compare groups.

RESULTS

The intervention intensity in the NMES group was less than half that in the volitional exercise group (31% versus 77% of maximum effort). Both groups experienced significant improvements in muscle structure and function (P < 0.001 to 0.019). Improvements in muscle characteristics and physical function were not different between groups. Exercise did not result in serious adverse events or increases in pain and disease activity. Attrition was 29% in the NMES group and 7% in the volitional exercise group.

CONCLUSION

Both NMES and high-intensity volitional resistance training can be used as effective approaches to improving muscle structure and function in patients with RA. NMES may be a viable alternative for improving muscle function in patients in whom high-intensity resistance exercise may not be tolerated or is contraindicated, but attrition must be considered when using this approach.