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

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

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Faculty of Human Kinetics, University of Lisbon, Lisbon, Portugal.



Longitudinal descriptive exploratory study.


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.


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


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.


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.


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.


abdominals; diastasis recti; ultrasound imaging

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