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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. The LA is a complex meshwork of connective tissue that comprises the tendinous insertions of the abdominal muscles, as well as the anterior and posterior rectus sheaths.1 As an anterior anchor for all the abdominal muscles, deformation 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. [ABSTRACT FROM AUTHOR]

STUDY DESIGN: Clinimetrics. OBJECTIVES: To investigate the intrarater between-session reliability of inter-rectus distance (IRD) measurement using ultrasound imaging in postpartum women with diastasis recti. BACKGROUND: Diastasis recti, a separation of the rectus abdominis muscles at the linea alba, occurs as a result of pregnancy and is characterized by increased IRD. The measurement of IRD in this population is of interest to determine changes in diastasis recti severity over time, or in response to treatment. Ultrasound imaging has been proposed as a useful tool to measure IRD in women with diastasis recti; however, the consistency of IRD measurement in this population using ultrasound imaging has, to our knowledge, never been investigated. METHODS: Ultrasound imaging was used to measure IRD in 20 women with diastasis recti on 2 different occasions. On each testing occasion, images were acquired at 4 locations along the linea alba while participants remained relaxed and while they performed a head lift to activate the rectus abdominis muscles. Reliability statistics included intraclass correlation coefficients, Bland-Altman analyses, minimum clinically important difference, and standard error of the measurement. RESULTS: Between-session reliability of IRD measurement was high, particularly when measuring IRD at or above the umbilicus, as indicated by intraclass correlation coefficients greater than 0.90 and low standard error of the measurement and minimum clinically important difference values (below 0.17 cm and 0.46 cm, respectively). Reliability coefficients were poorer when measuring IRD below the umbilicus. CONCLUSION: When performed by an experienced investigator, ultrasound imaging is a reliable tool by which to measure IRD in postpartum women who have diastasis recti. [ABSTRACT FROM AUTHOR]

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. J Orthop Sports Phys Ther 2013;43(7):495-503. Epub 30 April 2013. doi:10.2519/jospt.2013.4449 [ABSTRACT FROM AUTHOR]

STUDY DESIGN: Validation study. OBJECTIVES: To investigate the association between changes in electromyographic (EMG) signal amplitude and sonographic measures of muscle thickness of 4 abdominal muscles, during 2 clinical tests, in adults with and without lumbopelvic pain. BACKGROUND: There is a trend in rehabilitation to use ultrasound imaging (USI) to determine the extent of abdominal muscle contraction. However, the literature investigating the relationship between abdominal muscle thickness change and level of activation is inconclusive and has not included clinically relevant tasks.METHODS: Simultaneous recording from fine- wire EMG and USI was performed for 4 abdominal muscles, in 7 adults with lumbopelvic pain (mean ± SD age, 29.7 ± 12.0 years) and 7 adults without lumbopelvic pain (32.0 ± 10.6 years), during an active straight leg raise (ASLR) test and an abdominal drawing-in maneuver (ADIM). Cross-correlation functions and linear regression analyses were used to describe the relationship between the 2 measures. Analyses of variance were used to compare individuals with and without lumbopelvi pain, with an alpha set at .05. RESULTS: Across all muscles, peak cross- correlation values were low (ASLR, r = 0.28 ± 0.09; ADIM, r = 0.35 ± 0.11), and there was large variability in associated time lags (ASLR, τ = 0.69 ± 2.56 seconds; ADIM, τ = 0.53 ± 3.75 seconds) Regression analyses did not detect a systematic pattern of association between EMG signal amplitude and USI measurements, and analyses i variance revealed no differences between cohorts CONCLUSION: These results suggest a weak relationship between EMG amplitude and abdominal muscle thickness change measured with USI during the ADIM and ASLR, and raise questions about thickness change derived from USI as a measure of muscular activity for the abdominal musculature. J Orthop Sports Phys Ther 2013;43(7):466-477. Epub 30 April 2013. doi:10.2519/jospt.2013.4440 [ABSTRACT FROM AUTHOR]

The article presents a study to measure resting thickness of abdominal wall muscles and the perimuscular connective tissue (PMCT) that control spine. It includes a study conducted on patients with and without lumbopelvic pain (LPP) and included procedures using ultrasound imaging (USI). The article discusses results of the study that compare changes in linea alba, oblique abdominals and rectus abdominis.

The article explores the relationship between inter-recti distance (IRD) and the abdominal muscle performance in postpartum women. For this six-month follow-up study, 40 postpartum females participated where the trunk flexion, rotation strength, and endurance were measured. An improvement in the abdominal muscle performance and IRD of postpartum women was found, but those values did not reach the normal level after childbirth at six months.

The article explores the anatomy of the abdominal muscles as it related to imaging and summarizes the application of rehabilitative ultrasound imaging (RUSI) for assessment and training of the muscles. It discusses the effect of gender and body mass index on muscle thickness. It also highlights specific considerations regarding patient positioning, transducer selection and measurement options for imaging abdominal muscles.