Muscle mechanical properties of pelvic floor and paravertebral muscles in women with and without urge urinary incontinence: a case-control study

Abstract

Background: Muscle mechanical properties (MMPs) are relevant in the pathophysiology of lumbopelvic disorders. However, they have not been described in the pelvic floor muscles (PFM) and lumbar paravertebral muscles (LPM) of women with urge urinary incontinence (UUI). Objective: To identify differences between MMPs of PFM and LPM in patients with UUI and healthy controls. Secondarily also aimed to observe the relationship between sociodemographic and clinical variables with the PFM and LPM MMPs. Methods: The participants of this case-control study comprised 34 women with UUI (UUI group) and 34 continent women (control group). Sociodemographic variables were obtained together with data on the clinical status of the pelvic floor. The MMPs, i.e., frequency (tone), stiffness, decrement (inverse of elasticity), and viscoelastic properties (VP), such as relaxation time and creep, of PFM and LPM were assessed with a hand-held tonometer. Between-group differences and intra-group correlations were identified. Results: The UUI group presented higher frequency and stiffness, as well as lower relaxation time in PFM, whereas the LPM had lower tone and stiffness, and higher VP, compared to the control group (p < 0.05). The UUI group showed a pattern of moderate correlations (|0.403|<r<|0.600|) among all MMPs of PFM and tone, stiffness, and VP of LPM, which did not appear in the control group. Conclusión: The presence of UUI may influence MMPs at PFM and LPM levels, increasing the tone and stiffness of PFM, whereas these properties are reduced in LPM. These findings emphasize the clinical interest of the lumbopelvic determination of MMPs, obtained through externally applied hand-held instruments, in the pathophysiology of UUI.