Are Transversus Abdominus/Oblique Internal and Pelvic Floor Muscles Coactivated During Pregnancy and Postpartum?

Pereira L, et al.  Neurourol. Urodynam. 2012 Oct 15. Doi: 10.1002/nau.22315.
Michelle Spicka, DPT Pelvic PT Distance Journal Club Dec 5, 2012

Primary 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.

Subjects: 81 women divided into 4 groups:

1.       Nulliparous women without urinary symptoms
2.       Primigravid pregnant women at least 24 weeks gestational age
3.       Primiparous postpartum women after vaginal delivery with right mediolateral episiotomy
4.       Primiparous postpartum women after cesarean delivery with 40-60 days of postpartum

Study Design:  A clinical, controlled, prospective study was conducted.

Methods:  PFM and Tra/IO contractility was registered using surface EMG equipment (surface electrodes on abdominal wall and vaginal probe).  EMG protocol consisted of three maximal voluntary PFM contractions, recorded by the vaginal probe.  Each requested contraction was performed with a rest period of twise the time of the performed contraction in order to avoid muscle fatigue.  Later, three maximum voluntary Tra/IO contractions were requested.  PFM and Tra/IO electrical activities were simultaneously registered. 

Results: Only nulliparous women presented significant simultaneous Tra/IO and PFM co-activation when asked to contract PFM or Tra/IO. 

Discussion:

1.       Co-activation between Tra/IO and PFM occurs in normal physiological conditions  (Hodges, et al  in 2001)

2.       Several other authors have concluded that one cannot perform an effective pelvic floor contraction while relaxing the deep abdominal muscles which suggests that abdominal muscles have a strong influence on the pelvic floor performance

3.       The author’s findings from this paper are consistent with those of BØ, et al (Neurourol Urodyn 2009) showing that co-activation of the Tra/IO muscles typically occurs during the contraction of the PFM.

4.       Although there have been other studies in which a relationship between the co-activation of the Tra/IO and PFM in asymptomatic young women is demonstrated, there have not been studies concerning the behavior  of these muscles in the pregnancy and postpartum stages until now.

5.       Because EMG did not show simultaneous recording of the Tra/IO and PFM activity in primiparous women, one can infer that maternal adaptations can trigger changes in the motor behavior of those muscles.

6.       Also, the study did not find any significant co-activation in the postpartum women’s group, regardless of delivery mode which infers that pregnancy and postpartum influences muscle physiology, altering the abdominal-pelvic muscle synergy.

Conclusion: There is co-activation of the transversus abdominis/internal oblique and the pelvic floor muscles in young, asymptomatic nulliparous women and this pattern is modified in the primigravid pregnant and primiparous postpartum women.

Points from similar research:

1.       Hung et al (Man Ther 2010 Jun) found coordinated retraining diaphragmatic, deep abdominal and PFM function could improve symptoms and quality of life (cure/improvement rate was above 90% for patients who performed the exercise program).

2.       Talasz et al (Arch Gynecol Obstet 2012 Mar) found PFM dysfunction in healthy young women but were able to improve PFM function by using a training program that included co-contraction of the PFM and abdominal muscles.

3.       Neumann et al (In Urogynecol J Pelvic Floor Dysfunct 2002) found the TA and the IO were recruited during all pelvic floor muscle contractions and they concluded advice to keep the abdominal wall relaxed when performing PFM exercises is inappropriate and may adversely affect the performance of such exercises. 

4.       Sapsford et al (Int Urogynecol J 2012 Jan 26) found that specific abdominal muscle contractions can influence urethral closure in continent women which is probably mediated by concurrent activation of the PFM during the abdominal contraction.

5.       Arab et al (Neurourol Urodyn Jan 2011) used ultrasound imaging to determine the Tra/IO and PFM are co-activated.

Other thoughts:
1.       Should Tra/IO strengthening have a larger focus in the postpartum population (whether they have incontinence or not)?
2.       With all the evidence using accessory muscles or facilitory muscles with pelvic floor strengthening, is there ever a need to train an isolated pelvic floor contraction anymore?