Immediate Effect of Acupuncture on Electromyographic Activity of the Upper Trapezius Muscle and Pain in Patients With Nonspecific Neck Pain: A Randomized, Single-Blinded, Sham-Controlled, Crossover Study

Objective: The objective of this study was to assess changes in upper trapezius myoelectric activity and pain in patients with nonspecific neck pain after a single session of acupuncture (ACP). Methods: A blinded randomized clinical trial was conducted. Fifteen patients with nonspecific neck pain and 15 healthy participants were enrolled in a randomized, single-blinded, crossover study. Each participant was subjected to a single session of ACP and sham acupuncture (SACP). The electromyography (EMG) signal of the upper trapezius muscle was recorded during different step contractions of shoulder elevation force (15%-30% maximal voluntary contraction) before and after ACP treatment. Results: Significant effects were confirmed after the treatment (ACP and SACP) for Numeric Rating Scale scores (F-1,F-28 = 51.61; P < .0001) and pain area (F-1,F-2 = 32.03; P < .0001). Significant decreases in the EMG amplitude were identified for the nonspecific neck pain group (NPG) (F-1,F-112 = 26.82; P < .0001) and the healthy participant group (HPG) (F-1,F-112 = 21.69; P < .0001) after ACP treatment. No differences were identified between the ACP and SACP treatment protocols for Numeric Rating Scale score (NPG: F-1,F-28 = 0.95; P = .33), pain area (NPG: F-1,F-28 = 1.97; P = .17), or EMG amplitude (NPG: F-1,F-112 = 0.47; P = .49; HPG: F-1,F-112 = 0.75; P = .38). Conclusion: The effect of ACP at acupoints triple energizer 5 and large intestine 11 triple energizer 5, or in close proximity, contributes to pain relief among patients with nonspecific neck pain. The electromyographic analysis indicated a greater resistance to muscle fatigue and decrease of activity of the upper trapezius muscle among healthy participants and patients with nonspecific neck pain.