The Immediate Effects on Inter-rectus Distance of Abdominal Crunch and Drawing-in Exercises During Pregnancy and the Postpartum Period

J Orthop Sports Phys Ther. 2015 Oct;45(10):781-8. doi: 10.2519/jospt.2015.5459. Epub 2015 Aug 24.


Study design: Longitudinal descriptive exploratory study.

Objectives: To evaluate in primigravid women the immediate effect of drawing-in and abdominal crunch exercises on inter-rectus distance (IRD), measured at 4 time points during pregnancy and in the postpartum period.

Background: There is scant knowledge of the effect of different abdominal exercises on IRD in pregnant and postpartum women.

Methods: The study included 84 primiparous participants. Ultrasound images were recorded with a 12-MHz linear transducer, at rest and during abdominal drawing-in and abdominal crunch exercises, at 3 locations on the linea alba. The IRD was measured at 4 time points: gestational weeks 35 to 41, 6 to 8 weeks postpartum, 12 to 14 weeks postpartum, and 24 to 26 weeks postpartum. Separate 2-way, repeated-measures analyses of variance (ANOVAs) were performed for each exercise (drawing-in and abdominal crunch) and each measurement location to evaluate the immediate effects of exercises on IRD at each of the 4 time points. Similarly, 2-way ANOVAs were used to contrast the effects of the 2 exercises on IRD.

Results: Performing the drawing-in exercise caused a significant change in width of the IRD at 2 cm below the umbilicus, narrowing the IRD by a mean of 3.8 mm (95% confidence interval [CI]: 1.2, 6.4 mm) at gestational weeks 35 to 41, and widening the IRD by 3.0 mm (95% CI: 1.4, 4.6 mm) at 6 to 8 weeks postpartum, by 1.8 mm (95% CI: 0.6, 3.1 mm) at 12 to 14 weeks postpartum, and by 2.5 mm (95% CI: 1.4, 3.6 mm) at 24 to 26 weeks postpartum (P<.01). Performing the abdominal crunch exercise led to a significant narrowing of the IRD (P<.01) in all 3 locations at all 4 time points, with the exception of 2 cm below the umbilicus at postpartum weeks 24 to 26. The average amount of narrowing varied from 1.6 to 20.9 mm, based on time and location.

Conclusion: Overall, there was a contrasting effect of the 2 exercises, with the abdominal crunch exercise consistently producing a significant narrowing of the IRD. In contrast, the drawing-in exercise generally led to a small widening of the IRD.

Keywords: abdominals; diastasis recti; ultrasound imaging.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdominal Muscles / anatomy & histology*
  • Abdominal Muscles / diagnostic imaging
  • Abdominal Muscles / physiology*
  • Adult
  • Exercise / physiology*
  • Female
  • Gestational Age
  • Humans
  • Longitudinal Studies
  • Postpartum Period / physiology*
  • Pregnancy
  • Ultrasonography