Recently published scientific research confirms that the inter-rectus distance widens when the pelvic floor muscles and/or the pelvic floor muscles contract.

A diastasis rectus abdominis post-partum is quite common. The diastasis is measured with the inter-rectus distance. This is the distance between the two muscle bellies of the rectus abdominis muscle. There is no consensus as to what is a clinically significant inter-rectus distance. In literature this varies between 1.0 and 2.2 cm.

When a diastasis rectus abdominis is diagnosed, therapy mainly consists of exercises to close the inter-rectus distance by training the transverse abdominis muscles. However, if you take a closer look at the anatomical position it is interesting to see if the transverse abdominis muscles can actually close the gap.

It is also known that when you contract the pelvic floor muscles properly there is a co-contraction of the transverse abdominal muscles and visa versa. Hypothetically you could think that when you contract the pelvic floor muscles the diastasis rectus abdominis would close as well.

The objective of the research I will discuss is:

To identify the effect of a contraction of the pelvic floor muscles and transverse abdominis muscles on the inter-rectus distance.

Inclusion criteria:

• Healthy, primi- and multiparous women
• Single and multiple births
• Diastasis rectus abdominis ≥ 2 fingers widths at level of umbilicus, and/or 2 cm below and above the umbilicus

Exclusion criteria:

• Inability to perform correct pelvic floor muscle and/or transverse abdominis contraction
• Pregnancy
• Inadequate comprehension of Scandinavian language
• Chronic physical or mental illness

The primary outcome measure was the change in inter-rectus distance measured with ultrasonography 2 cm above and 2 cm below the umbilicus.

The pelvic floor muscles were assessed by:

• An experienced women’s health physiotherapist by inspection and vaginal palpation
• Ultra-sonography

The transverse abdominal muscles were assessed with ultrasound. Before the inter-rectus distance was measured a correct contraction of the muscles was checked.

Inter-rectus distance was measured in the following order:

At rest

1. During pelvic floor muscle contraction
2. During transverse abdominis muscle contraction
3. During combined pelvic floor muscle (start) and transverse abdominis contraction (after contraction of pelvic floor muscles)

Results:

In total 38 women with a mean age of 34.6 (SD 4.0) and a mean of 15.1 (SD 5.9) weeks post-partum were included.

There was a significant increase in inter-rectus distance with a:

• Contraction of the pelvic floor muscles
• Contraction of the transverse abdominis muscles
• Combined contraction of the pelvic floor and transverse abdominis muscles

At 2 cm above and 2 cm below the umbilicus.

Contraction of the pelvic floor muscles alone resulted in the smallest increase.  A contraction of the transverse abdominis muscle showed a larger increase and the largest increase was when both muscles where combined (pelvic floor + transverse abdominis muscle).

There is an indication that a contraction of the pelvic floor muscles and the transverse abdominis muscles increase the inter-rectus distance. The increase of the inter-rectus distance due to pelvic floor muscle contraction is small.

However: the increases found in this research were within the limits of the measurement error. This means that it is not sure that the increase is due to the contracting muscles.

Clinical implications (personal opinion):

So a contraction of the pelvic floor muscles and transverse abdominis muscles increase the inter-rectus distance. We know from other research that a contraction of the rectus abdominis muscle (a crunch) narrows the inter-rectus distance.

So with this in mind is an abdominal crunch (without a contraction of the transverse abdominis musle) the best exercise for women with a diastasis rectus abdominis?

Well I don’t think so and my opinion is based on the research of Lee and Hodges and my clinical observations:

Previous research by Lee, Hodges and Mota has already shown that a contraction of the rectus abdominis muscle (curl-up) without a preactivation of the transverse abdominis reduced the inter-rectus distance. With preactivation of the transverse abdominis muscle the inter-rectus distance was the same or wider during a curl-up.

Lee and Hodges hypothesise that if you solely focus on narrowing the inter-rectus distance, you forget that support of the abdominal content is compromised. This might result in less mechanical function and above all in a less cosmetic appearance. However, as the above is a hypothesis more research is needed.

Women who visit us in the clinic often have the aim to decrease the diastasis rectus abdominis.  I think that it is more important to explain the biomechanics of the muscles of the abdominal wall.

‘So, that not a decrease of the inter-rectus distance but improvement of the abdominal wall should be the main objective of training’.

References:

N.M. Theodorssen, L.I. Strand, K. Bø. Effect of pelvic floor and transversus abdominis muscle contraction on inter-rectus distance in postpartum women: a cross-sectional experimental study. Physiotherapy: 105(2019) 315-322

D. Lee, P.W. Hodges. Behavior of the linea alba during a curl-up task in diastasis rectus abdominis: an observational study. Journal of orthopaedic & sports physical therapy. Volume 46 (2016), number 7 580-587