The effect of action potential simulation on post dry-needling soreness in the treatment of active trapezius myofascitis
Introduction: Myofascial Pain Syndrome (MPS) is a painful and prevalent muscular condition. It is characterized by the development of Myofascial trigger points (TrPs) that are locally tender when active and which can refer pain through specific patterns to other areas of the body distal from the trigger point. There exist many types of treatments for MPS of which dry needling is one of the most effective forms. However, a very common side-effect experienced is postneedling soreness, which when compared to trigger point injections are more painful, with respect to both intensity and duration. Studies have shown that the exact cause of post-needling soreness has not been clearly documented. Action Potential Simulation (APS) Therapy operates using a direct electric current (DC) on muscles. It stimulates action potentials that are stronger than the natural nerve impulses. It operates on a similar principle to the gate control theory of Melzack and Wall (1988) which results in the inhibition of nociceptive signals. Stimulation by the APS unit creates a normal action potential that restores the inherent biochemical processes in the region. This low to medium frequency current (below 150 Hz) has been reported to alleviate pain, decrease inflammation, enhance blood circulation and aid in wound and bone fracture healing. Methodology: This study was designed as a prospective, randomised, controlled experimental investigation. Sixty subjects were randomly allocated into three equal groups of 20 subjects each. Group One received the fanning dry needling technique; Group Two received a combination of fanning dry needling plus APS Therapy. Group Three was the control group in which the subjects were treated with fanning dry needling with „Sham‟ APS Therapy. Algometer and Numerical Pain Rating Scale 101 (NRS 101) readings were taken immediately before and after the dry needling procedure and again at the follow-up visit 24 hours later. Subjects used a 24-hour pain diary and the NRS 101 scale which was filled out at 3 hour intervals, to record any post-needling soreness. Results: An intra-group analysis revealed that, objectively and subjectively, all groups experienced some degree of post-needling soreness, which deceased significantly over time. This decrease of pain was not significantly related to the treatment group, and there is no evidence of the differential time effect with the treatment. An inter-group analysis yielded no statistically significant results regarding the effectiveness of the treatments received by the patients. This could be because of the small sample size or because „„Sham‟‟ APS is not a useful intervention. Conclusion: The results from this study revealed that all three treatment groups responded equally in the alleviation of pain. However, the dry-needling treatment group alone (Group One) revealed a much more significant decrease in pain compared to the other two. It can thus be concluded that APS Therapy had no significant beneficial effects on post-needling soreness.