Normative myotonometric values of pelvic floor and lumbar paraspinal muscles in women

Muscle mechanical properties (MMPs) of pelvic floor (PFM) and lumbar paraspinal muscles (LPM) are used to characterize musculoskeletal behavior in women. However, side‑specific normative data and their associations with female‑specific factors remain limited. This study aimed to establish side‑specific normative values, and examine the effects of age, body mass index (BMI), vaginal delivery, menopausal status and physical activity. The MMPs (frequency, stiffness, logarithmic decrement, relaxation and creep) of 116 healthy women (18–65 years) were obtained for PFM and LPM on the right and left sides using a handheld myotonometric device. Overall, bilateral symmetry was observed for most MMPs, although small asymmetries emerged mainly in PFM viscoelastic parameters within specific subgroups. Age and BMI showed negligible relations with PFM (Spearman’s correlation (r s ) < 0.20), whereas age was positively associated with frequency (r s = 0.25–0.40), stiffness (r s = 0.45–0.53) and decrement (r s = 0.59–0.60), and negatively associated with relaxation in LPM. Vaginal delivery was associated with modest changes in PFM viscoelastic properties (creep: 0.28 < rank-biserial correlation (r rb ) < 0.32) and greater increases in LPM tone and stiffness (0.30 < r rb < 0.51). Menopausal status was associated with increased stiffness (> 150 N/m) and reduced viscoelasticity at LPM level. Physical activity showed minimal associations. These findings indicate region‑dependent lumbopelvic muscle behavior shaped by female‑specific biological factors, supporting bilateral and region‑specific assessment when using myotonometry.