Characterizing core muscle morphometry in postpartum women with pelvic girdle pain and asymptomatic subjects: a comparative cross-sectional study.

Background: This study aimed to examine the differences in core muscle morphometry and contraction changes between postpartum individuals with and without pelvic girdle pain (PGP). Understanding the observed changes in muscle thickness and contraction characteristics is crucial for tailoring effective core muscle rehabilitation strategies that promote optimal postpartum recovery. Methods: A cross-sectional study was conducted involving 150 postpartum women with PGP and 50 asymptomatic individuals as matched controls. Real-time musculoskeletal ultrasound was used to measure core muscle morphometry and assess changes in muscle thickness and percentage change during various tasks. Results: Compared with asymptomatic women, individuals with PGP exhibited substantially reduced diaphragm excursion and thinner muscle thickness of the transverse abdominal muscle (TrA) during active straight leg raise (ASLR) tests with abdominal muscle contractions (P < 0.05). The TrA respiratory contraction rate and preferential activation ratio during abdominal breathing were also lower in the PGP group (PGP = 0.46 (0.13 to 1.41); asymptomatic women = 0.98 (0.05 to 2.05), P = 0.01). In addition, postpartum women with PGP showed increased activation of the internal oblique muscle during ASLR tests with abdominal muscle contractions compared to controls (PGP: 47%; asymptomatic women: 45%, P < 0.05). Furthermore, the bilateral lumbar multifidus muscle was smaller and thinner on the right side in the PGP group than the asymptomatic group (P < 0.001). Conclusion: Postpartum women with PGP exhibited thinner muscle thickness on core muscle morphometry and less muscle change during abdominal breathing and the ASLR test.