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

Mota PGF, Pascoal AGBA, Carita AIAD, Bø K.  JOSPT October 2015, volume 45, number 10

Pelvic Distance Journal Club November 2015     

Trisha Jenkyns PT, DPT, WCS            

Study Objective/Purpose

Primary goal

·         To look at 2 abdominal-strengthening exercises,

o   Drawing-in and the abdominal crunch

·         The effect of these 2 exercises on the Inter Rectus Distance (IRD) at certain time points:

o   Gestational weeks 35 to 41

o   Postpartum at 6-8, 12-14, and 24-26 weeks

Secondary goal:

·         Contrast the effects of the 2 exercises

Brief Background: 30 -70% women may experience DRA in pregnancy and it may remain in 60% of postpartum women.  DRA has also been found in 52% of gynecological menopausal patients.

The reported prevalence of DRA varies in the literature and may be inaccurate because there are different definitions in the literature and different ways it is measured (palpation, calipers and US-gold standard). There are not many studies that define the normal inter-rectus distance or what the risk factors are for DRA.  The definition varies in the literature and as of yet, there is no international consensus on the best measurement location. 

·         Risk factors: multiparity, maternal age, childcare responsibilities and weight gain have been associated with DRA

·         DRA has also been defined as an IRD of greater than 25 mm at 1 or more locations. 

·         In another study, commonly referenced, Beer et al (2009) used US imaging and state that in nulliparous women the linea alba should be considered normal when the IRD is less than 15 mm at the xiphoid level, 22 mm at 3 cm above the umbilicus, and 16 mm at 2 cm below the umbilicus.  A DRA is commonly diagnosed when the width exceeds these amounts.

·         Mota et al. make the point that the drawing-in exercise is being recommended for pregnant/postpartum women and also for the general population and that it is being used to ostensibly help prevent and or reduce DRA…without data to support this recommendation.

·         Mota et al. state there are no high quality clinical studies to support theories about DRA causing long term sequelae  like lumbo-pelvic pain and abnormal posture.

Methods

Study Design      Longitudinal descriptive exploratory study

Target Population  

Participants: Various professionals in the community referred women attending prenatal courses in the Lisbon, Portugal area to the study 

·   Inclusion criteria: Primaparas, had to agree to participate in 4 testing sessions and have ability to perform the 2 different abdominal exercises

·   Exclusion criteria: Any conditions affecting the ability to perform ADL, any symptoms that required medical attention (i.e., high-risk pregnancy, delivery before gestational week 37, previous spinal or abdominal surgery, and neuromuscular diseases) and if any of the 4 testing sessions were missed

123 women agreed to participate in this study, and 84 completed all 4 testing sessions

Instrumentation & Procedures

Participant was in hook-lying position

·         Before measurement, participants were verbally instructed in exercises

o   Ab crunch: participants were instructed to raise shoulders blades were off surface

o   Drawing-in exercise: first it was determined with US that the TrA was activated; if necessary participants were shown US biofeedback to help activate TrA

·         Images were collected at the end of exhalation

·         Investigator was careful not to apply too much pressure with probe in order to avoid reflex response

US images were recorded with a 12-MHz linear transducer

·         At rest, during abdominal drawing-in and abdominal crunch

·         Measured at 3 locations

o   2 cm below umbilicus

o   2 cm above

o   5 cm above

·         The IRD was measured at 4 time points:

o   Gestational weeks 35-41

o   6-8 weeks postpartum

o   12-14 weeks postpartum

o   24 -26 weeks postpartum

Physical therapist performed all measurements.  PT had 10 years experience, special US training, 3 years of experience assessing IRD and was blinded to the identification of women and to previous IRD measurements.

·         Prior to study, reliability was established for test/retest measurements and demonstrated good to very good reliability (Intraclass correlation coefficients ICC’s between 0.74-0.90) except for the measurement 2 cm below … ICC was 0.50

·         Testing order: rest, drawing-in, contraction was maintained for 3-5 sec and there was a 6-10 sec interval between measurements

·         At each location 3 measurements were made (rest, drawing-in and crunch)

·         Participants were requested not to “practice abdominal crunch or drawing in between testing sessions during study

Statistical Analysis

For each exercise and each measurement location, a separate 2-way ANOVA was performed to evaluate the effect.  When a significant interaction was found, t-tests were used to indicate if difference was significant

Results

·         Demographic data

o   Table 1: Age, gestational week of birth, birth weight of baby, university education, vaginal or cesarean delivery

o    Table 2: Weight of women and whether or not they were participating in regular exercise classes 2 or more times/week

o   Table 3 & 4: Descriptive statistics for the IRD changes during the exercises at each locations and for each time point.  Important to first define ‘Effect of Exercise’

§  EFFECT OF EXERCISE  = IRD during exercise – IRD at rest

·         THEREFORE a positive value represents a widening and negative represents a narrowing

Summary

Drawing-in:

·         2 cm below the umbilicus: drawing-in exercise caused a significant (p<.001) narrowing during pregnancy (35-41 weeks gestation) AND during postpartum there was a significant (p<.0125) widening at this level for all 3 postpartum measurements

o   IRD significantly increased during postpartum below the umbilicus with minimal changes above the umbilicus

·         2 & 5 cm above the umbilicus, there were significant differences between the resting and abdominal drawing-in exercise conditions at all 4 measurement times (pregnancy & postpartum)

·         When the individual time points were considered…the changes were considered small and mostly not significant

Abdominal Crunch:

·         Narrowing of IRD was statistically significant (P<.0125) at each measurement time, but of varied magnitude at all points for all 3 locations, EXCEPT during 24-25 postpartum at 2 cm below

COMPARING THE 2 EXERCISES:

·         Performing the abdominal crunch exercise generally led to a significant narrowing of the IRD, and the drawing-in exercise generally led to a small widening of the IRD.

o   Meanwhile, it is commonly thought and is found in the literature that activation of the transversus abdominis muscle could be protective of the linea alba and may help to prevent or reduce DRA

Authors’ Discussion and Conclusions

Strengths: First study to follow a cohort of women from pregnancy to 6 months postpartum, number of participants, checking DRA at 3 different locations, use of US which is reliable measurement method, and blinding of the investigator

Limitation:  lack of pre-pregnancy assessment, the order of testing should have been randomized

Often when measurements are made, it is common and even advised to measure 3 times and use the mean of the three, but the authors chose to take 1 measurement, because of the effort required doing the exercises, especially for the pregnant measurement.

Only the immediate effect was studied, so the authors make it clear that these data cannot be used to suggest effectiveness of treatment as an intervention of exercise.

Applicability: What is the best approach for treatment of DRA?