Acute Pain Reduction Effects of Electrical Muscle Stimulation in Myofascial Pain Syndrome: Comparison with Standard Treatments.

Introduction: Over half of working adults experience upper back pain, often due to myofascial trigger points (MTPs) in the trapezius muscle (TM). These sensitive knots form from muscle overload, leading to pain, which contributes to myofascial pain syndrome (MPS). Standard treatments such as passive stretching (PS) and trigger point pressure release (TPR) offer long-term relief [1]. This study compared these methods to a new approach: electrical muscle stimulation with active stretching (EMS+AS), for acute effects on MPS. EMS+AS targets the muscle opposite the MTP, creating resistance during a stretch, potentially enhancing its effectiveness.
Methods: We investigated whether EMS+AS reduces pain intensity (PI) and increases pressure pain threshold (PPT) – a measure of MTP sensitivity – compared to standard treatments, including PS, TPR, TPR+AS, and the combination of EMS, AS, and TPR (EMS+AS+TPR). Five tasks were administered in random order to all participants with MTPs in the upper or middle TM. All treatments consisted of 3 sets of 10-second applications with 10-second rest periods (one minute). There was a 2-minute rest between tasks. The EMS used square pulses with adjustable intensity, delivered at a constant current of 20 Hz and a pulse width of 100 μs. Two electrodes were placed across the muscle line on the opposite end of the MTP location to stimulate muscle contraction, generating active resistance during active stretching (AS) of the TM. Participants performed shoulder depression or scapular retraction for 10 seconds after releasing the electri-cal stimulation for 3 seconds. PI and PPT were measured before and after each treatment, and a paired t-test was ana-lysed. The results of all the treatment groups were compared by ANOVA.
Results: The study included 65 participants (24 males, 41 females) with a mean age of 37.47 ± 12.51 years old. EMS+AS significantly reduced PI and increased PPT (p < .001) (Tab 1). PI did not differ significantly between treatments, but there was a significant difference in PPT among the five treatments (F (4,320) = 2.948, p = < .001). Combination therapy (EMS+AS+TPR) showed the greatest improvement in PPT, however, EMS+AS showed the greatest improvement in PI.
Discussion and conclusion: These results suggest that combination therapy shows promise in reducing MTPs. The effectiveness of EMS application within the combination therapy might be due to synergistic effects that decrease muscle tension. This is likely because dedicated EMS devices can provide more immediate and effective results, similar to the principles behind the proprioceptive neuromuscular facilitation (PNF) technique [2]. Therefore, applying EMS with stretching can effectively manage acute pain reduction in MPS compared to standard treatments. Future studies com-paring EMS+AS to sham stimulation and transcutaneous electrical nerve stimulation (TENS) are needed. Additionally, using electromyography (EMG) and ultrasound imaging could provide further insights into MTPs and pain mechanisms. Ultimately, this EMS design would be developed for a programmable shoulder pad device used in rehabilitation care.