EFFECTS OF ELECTRICAL MUSCLE STIMULATION ON MYOFASCIALS PAIN SYNDROME: A PRELIMINARY STUDY

Introduction: Many working adults suffer from upper back pain, especially in the trapezius muscle (TM). The myofascial trigger point (MTP) is formed by muscle overload, leading to cell ischemia and contributing to myofascial pain syndrome (MPS). MTPs cause discomfort and reduce muscle function. Current treatments reverse MTPs through com-bination therapy of passive stretching, and trigger point pressure release (TPR), which addresses the long-term effects [1]. However, electrical muscle stimulation (EMS) has the potential to show immediate effects on improving pain by facilitating greater stretch in the affected TM. This study aimed to evaluate the acute effects of EMS on MPS and compare changes in pain intensity (PI), pressure pain threshold (PPT) (both indicators of the MTP sensitivity), and EMG activity in response to different MPS treatments.

Methods: Twelve healthy volunteers (4 males and 8 females; age 36.67 ± 12.02 years old), with an MTP in the TM were treated by 5 treatments (T1-T5) applied in a random order: (T1) passive stretching in the upper or middle TM sections, (T2) TPR, (T3) TPR combined with active TM stretching, (T4) active TM stretching with shoulder depression or scapular protraction combined with EMS, and (T5) a combination therapy of TPR and T4 (Fig. 1). The EMS consist-ed of a biphasic, stimulation frequency of 20 Hz with pulse width of 100 µs, and constant current amplitude adjusted for comfort level. The electrodes were applied at the opposite end of the MTP location to stimulate muscle contraction in the region. In doing so, this region would produce active resistance to the applied stretch, encouraging a greater stretch of the TM. The treatment was provided for 10s repeated 3 times with a 10s interval in between. After each treatment the participant rested for 2 minutes. sEMG recording of the MTP region of TM were taken during TM stretching and TM contraction (shoulder elevation or scapular retraction) to evaluate difference in magnitude and frequency of EMG. Differences in PI, PPT and EMG as a result of each treatment were evaluated using ANOVA.

Results: Post T4, significant differences were observed in PI (t (11) = -4.022, p = .002) and PPT (t (11) = 4.492, p < .001). Median frequency (MDF) significantly increased during TM action after treatments, but there was no difference amplitude (RMS) (Tab. 1). Combination therapy showed a significant decrease in RMS during TM stretching (F (4, 52) = 15.456, p < .001).

Discussion and conclusion: The results indicated that EMS applied during stretching has a significant acute effect on MPS, as evidenced by a reduction in pain (decreased PI and increased PPT) and an increase in EMG frequency during TM action which suggests improved muscle performance, and cell perfusion. Combination therapy showed promise in reducing MTP, which was possibly due to synergistic effects in optimizing muscle contraction which can break energy crisis [2]. However, it is important to note that the data was not segmented by TM sections, limiting the precision of the findings. Future investigations should consider sham stimulation and electrical nerve stimulation.