Physiological rationales of physical therapy interventions in the management of primary dysmenorrhea: a critical review

Background: The mechanisms underlying the physical therapy interventions for obtaining relief from primary dysmenorrhea (PD) symptoms are not fully understood. Objective: To provide an overview of the physiological rationales from randomized controlled trials (RCTs) on how physical therapy interventions in the management of PD might work. Methods: Databases CINAHL, PEDro, Embase, Web of Science, Ovid Medline, and AMED were searched from database inception to October 2014 using related terms for dysmenorrhea and physical therapy interventions. Trials were independently selected and data extracted by two reviewers. Results: The search yielded 287 citations; 26 RCTs met the inclusion criteria and were included for review. Among the 26 included trials, eight trials on acupressure, seven on acupuncture, and five on TENS, two on spinal manipulation, one on low-level light therapy (LLLT), one on heat, one on far-infrared ray, and one on yoga were identified. The predominant physiological rationales identified in the RCTs are endogenous opioid mechanisms (n = 12), gate-control theory (n = 8), and traditional Chinese medicine (TCM) theory (n = 6). A few trials reported up to four different rationales. Conclusions: The analgesic effect of acupuncture is primarily through the release of endogenous opioids and hormones. In addition, practitioners of TCM believe that acupuncture alleviates pain of PD by regulating the prostaglandin levels. Acupressure, heat, high frequency transcutaneous electrical nerve stimulation (TENS), and yoga are proposed to work by segmental inhibition of pain pathway.