Are transversus abdominis/oblique internal and pelvic floor muscles coactivated during pregnancy and postpartum?

AIM: The aim of this study was to simultaneously evaluate both transversus abdominis/internal oblique (Tra/IO) and pelvic floor muscles (PFM) during isometric exercises in nulliparous, pregnant, and postpartum women. METHODS: The study included 81 women divided into four groups: (G1) nulliparous women without urinary symptoms (n = 20); (G2) primigravid pregnant women with gestational age ≥24 weeks (n = 25); (G3) primiparous postpartum women after vaginal delivery with right mediolateral episiotomy (n = 19); (G4) primiparous postpartum women after cesarean section delivery, with 40 to 60 days of postpartum (n = 17). The assessment consisted of simultaneous surface electromyography (EMGs) of the PFM and Tra/IO, during three isometric maximum voluntary contractions. RESULTS: Only nulliparous women presented significant simultaneous Tra/IO and PFM co-activation when asked to contract PFM (P = 0.0007) or Tra/IO (P = 0.00001). CONCLUSIONS: There is co-activation of the transversus abdominis/internal oblique and the pelvic floor muscles in young, asymptomatic nulliparous women. This pattern was modified in primigravid pregnant and primiparous postpartum women regardless of the delivery mode.