Transcutaneous Electrical Nerve Stimulation Reduces Movement-Evoked Pain and Fatigue: A Randomized, Controlled Trial

Abstract

Objective: Fibromyalgia (FM) is characterized by pain and fatigue, particularly during physical activity. Transcutaneous electrical nerve stimulation (TENS) activates endogenous pain inhibitory mechanisms. This study was undertaken to investigate if using TENS during activity would improve movement-evoked pain and other patient-reported outcomes in women with FM.

Methods: Participants were randomly assigned to receive active TENS (n = 103), placebo TENS (n = 99), or no TENS (n = 99) and instructed to use it at home during activity 2 hours each day for 4 weeks. TENS was applied to the lumbar and cervicothoracic regions using a modulated frequency (2-125 Hz) at the highest tolerable intensity. Participants rated movement-evoked pain (primary outcome measure) and fatigue on an 11-point scale before and during application of TENS. The primary outcome measure and secondary patient-reported outcomes were assessed at baseline (time of randomization) and at 4 weeks.

Results: After 4 weeks, a greater reduction in movement-evoked pain was reported in the active TENS group versus the placebo TENS group (group mean difference -1.0 [95% confidence interval -1.8, -0.2]; P = 0.008) and versus the no TENS group (group mean difference -1.8 [95% confidence interval -2.6, -1.0]; P < 0.0001). A reduction in movement-evoked fatigue was also reported in the active TENS group versus the placebo TENS group (group mean difference -1.4 [95% confidence interval -2.4, -0.4]; P = 0.001) and versus the no TENS group (group mean difference -1.9 [95% confidence interval -2.9, -0.9]; P = <0.0001). A greater percentage of the patients in the active TENS group reported improvement on the global impression of change compared to the placebo TENS group (70% versus 31%; P < 0.0001) and the no TENS group (9%; P < 0.0001). There were no TENS-related serious adverse events, and <5% of participants experienced minor adverse events from TENS.

Conclusion: Among women who had FM and were on a stable medication regimen, 4 weeks of active TENS use compared to placebo TENS or no TENS resulted in a significant improvement in movement-evoked pain and other clinical outcomes. Further research is needed to examine effectiveness in a real-world setting to establish the clinical importance of these findings.

Trial registration: ClinicalTrials.gov NCT01888640.

Figure 1

Study design and Consolidated Standards of Reporting Trials (CONSORT) diagram. A, Study design for all 4 visits. At visit 1, participants were screened for pain and fibromyalgia (FM) according to the American College of Rheumatology 1990 criteria 32. At visit 2, subjects were re‐screened for pain and randomized into treatment (Tx) groups. Baseline questionnaires were assigned, and subjects were assessed for pain and fatigue at rest and during functional tasks. Transcutaneous electrical nerve stimulation (TENS) was applied during visit 2 and remained turned on for 30 minutes prior to reassessment of pain, fatigue, and function. Participants were given the TENS unit for home use over a 4‐week period before returning for visit 3. Visit 3 followed the same protocol as visit 2. After visit 3, all subjects received active TENS for 4 weeks and were reassessed with the same protocol as visits 2 and 3. All assessments were the same across treatment arms. B, CONSORT diagram. We assessed 1,046 participants for eligibility, with 468 excluded prior to enrollment. The main reasons for exclusion were previous TENS use and a pain level of <4 on a 10‐point numerical rating scale. Following enrollment at visit 1, 5 subjects did not meet the criteria for FM, and 1 week later at visit 2, 14 subjects were excluded for having a pain level of <4. After enrollment on visit 1, 17 subjects withdrew from the study due to personal reasons. Thus, the remaining 301 participants were then randomly assigned to receive active TENS (n = 103), placebo TENS (n = 99), or no TENS (n = 99). Color figure can be viewed in the online issue, which is available at http://onlinelibrary.wiley.com/doi/10.1002/art.41170/abstract.

Figure 2

Active transcutaneous electrical nerve stimulation (TENS) use significantly decreased pain and fatigue in women with fibromyalgia during activity and at rest compared to placebo TENS or no TENS use, per intent‐to‐treat analysis. Graphs show movement‐evoked and resting pain and fatigue before and during treatment at visits 2 and 3. Between visits 2 and 3, participants used TENS at home for 4 weeks (dotted lines). A, Movement‐evoked pain during the 6‐minute walk test (6MWT). B, Movement‐evoked pain during a 5‐time sit‐to‐stand test (5TSTS). C, Resting pain. D, Movement‐evoked fatigue during the 6MWT. E, Movement‐evoked fatigue during the 5TSTS. F, Resting fatigue. * = P < 0.05 versus placebo TENS and no TENS. Data are the mean ± SEM.

Figure 3

The active TENS group had an improved perception of change and a greater number of responders with regard to the degree of change in movement‐evoked pain or fatigue during a 6MWT compared to the placebo TENS or no TENS groups. A, The percentage of participants who reported feeling better or much better (blue), no change (green), and worse or extremely worse (red) after 4 weeks of active TENS, placebo TENS, or no TENS treatment. The majority of individuals reported a significant overall improvement after using active TENS compared to those who used placebo TENS or no TENS (P < 0.0001). There were no differences between the placebo TENS and no TENS groups (P = 0.175). B, Percentages (with 95% confidence intervals [95% CIs]) of subjects in each treatment group who had a clinically meaningful response to TENS (as described by Arnold and colleagues 43, i.e., ≥30% reduction [pain], ≥20% reduction [fatigue, function]). There was a significantly greater number of responders for pain, fatigue, and both pain and fatigue in the active TENS group compared to the placebo TENS and no TENS groups. Function was measured according to the Revised Fibromyalgia Impact Questionnaire 39. See Figure 2 for other definitions. Color figure can be viewed in the online issue, which is available at http://onlinelibrary.wiley.com/doi/10.1002/art.41170/abstract.