Immediate Effect of Active Abdominal Contraction on Inter-recti Distance.

STUDY DESIGN: Controlled laboratory study. BACKGROUND: Inter-recti distance (IRD) is the measurement of the linear distance between the medial aspects of the rectus abdominis muscle. Inter-recti distance has been reported to decrease in postpartum women during a curl-up maneuver. OBJECTIVE: To determine if IRD decreases with active abdominal contraction in men and in nulliparous and parous women. METHODS: Fifty-six subjects (male, 11; nulliparous female, 22; parous female, 23) participated. Inter-recti distance was measured with the abdominal muscles at rest and during active contraction (curl-up), at 2 locations (above and below the umbilicus), using ultrasound imaging. A mixed-model, repeated-measures analysis of covariance was used for each of the 2 locations, to determine whether IRD differed between contraction states among the 3 groups, with age and umbilicus circumference as covariates. When significant differences were found, planned t test comparisons were made. RESULTS: The parous group's IRD significantly decreased from rest to contraction at both locations, whereas the nulliparous and male groups' IRD did not significantly change from rest to contraction. The nulliparous group's IRD was significantly narrower than the other groups at rest at both locations, and narrower than the parous group during active contraction. CONCLUSION: Parous women had a narrower IRD in the curl-up condition than at rest, as hypothesized. However, an unexpected finding of a lack of significant within-group change in IRD in nulliparous women and men occurred. Findings suggest that the IRD in men may only differ from that of nulliparous women.

Concurrent validity of calipers and ultrasound imaging to measure interrecti distance.

STUDY DESIGN: Clinical measurement, concurrent validity criterion standard. OBJECTIVE: To determine the concurrent validity of digital nylon calipers in comparison to ultrasound imaging (USI) for the measurement of interrecti distance (IRD). BACKGROUND: Diastasis rectus abdominis is the abnormal increase in the width of the linea alba, measured as IRD. A diastasis rectus abdominis can compromise mechanical trunk function in both genders. IRD has been accurately measured with USI but requires costly equipment and extensive examiner training. Digital nylon calipers are inexpensive and easy to use, but their use to measure IRD has not been validated. METHODS: A sample of convenience of 56 individuals (11 men, 45 women) was measured. A single examiner was assigned to each tool (calipers or USI), and IRD was measured at 2 locations (above and below the umbilicus) under 2 conditions (abdominal muscles at rest and abdominal muscles contracted). All measurements were made during a single session, and examiners were blinded to measurements with the other tool. RESULTS: Above the umbilicus, the measurements of IRD with calipers were similar to those made with USI, with intraclass correlation coefficients (model 3,2) of 0.79 with abdominal muscles at rest and 0.71 with abdominal muscles contracted. The absolute mean difference between the caliper and USI measurements of IRD above the umbilicus was 0.03 cm larger with the calipers when the abdominal muscles were at rest and 0.03 cm smaller when the abdominal muscles were contracted. The values of IRD obtained with the caliper and USI techniques were not comparable when obtained below the umbilicus. CONCLUSION: The calipers are a valid tool for measuring IRD above the umbilicus in males and females. Measuring IRD with calipers below the umbilicus should not be considered valid, using USI as the criterion standard. This may reflect anatomical variation of the linea alba or a limitation of the calipers to assess IRD at the same depth as USI.