Surface Electromyography Characteristics of Pelvic Floor Muscles in Healthy Women, Pelvic Floor Dyssynergia, and Urinary Incontinence: A Retrospective Comparative Study

BACKGROUND Surface electromyography (sEMG) of pelvic floor muscles (PFM) offers insights into neuromuscular control but lacks standardized normative values. This study aimed to evaluate baseline and contractile sEMG signal characteristics - including root mean square (RMS) amplitude in microvolts and normalized to maximum voluntary contraction (%MVC) - in a healthy control (H) group, pelvic floor dyssynergia (DS) group, and urinary incontinence (UI) group. MATERIAL AND METHODS A retrospective analysis included 68 women (H=28, UI=22, DS=18). UI was confirmed by the International Consultation on Incontinence Questionnaire-Short Form, and DS diagnosed via anorectal manometry. sEMG was recorded with a intravaginal probe using the Glazer protocol. RMS and %MVC were analyzed using Bayesian multivariate regression adjusted for age and BMI. RESULTS No significant differences were found at baseline rest or rapid contractions (P>0.05). The DS group showed higher RMS during tonic contractions vs H group (Δ=4.20, 95% BCI [0.99, 7.29], P<0.05) and UI (Δ=3.44, 95% BCI [0.48, 6.20], P<0.05), and impaired post-tonic relaxation vs H group (Δ=1.13, 95% BCI [0.10, 2.15], P<0.05). Normalized to %MVC, DS group showed lower rapid contraction activity than H group (Δ=-10.49, 95% BCI [-19.46, -1.86], P<0.05). H group outperformed UI group in tonic contraction (P<0.05). CONCLUSIONS DS showed higher RMS amplitudes during tonic contractions, impaired relaxation, and reduced %MVC efficiency, indicating paradoxical activity. UI patterns were heterogeneous, highlighting its multifactorial nature. Reliance on raw RMS alone may misclassify dysfunctions; multiparametric assessment and validation in larger cohorts are needed.