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STUDY DESIGN: Test-retest intrarater reliablity study. OBJECTIVE: To examine reliability of abdominal musculature measurements across a broad range of conditions for a physical therapist newly trained in assessment using rehabilitative ultrasound imaging (RUSI).BACKGROUND: RUSI has previously been used to assess abdominal muscle function during a drawing-in maneuver of the anterior abdominal wall, and measurements conducted by an experienced assessor have been validated by comparison with magnetic resonance imaging. Few studies have examined the reliability of less experienced operators, and only in isolated measurement conditions.METHODS AND MEASURES: Nineteen subjects (11 female, 8 male) without a history of low back pain performed the abdominal drawing-in maneuver in a supine hook-lying position. RUSI was used bilaterally to assess the thickness of the internal oblique (10) and transversus abdominis (TrA) muscles at rest and on contraction, as well as changes in the length of the TrA muscle (indicated by slide of the anterior abdominal fascia). The reliability of a novice rater who received 8 hours of training was examined (a) across 3 measurements of the same ultrasound image, (b) across 3 separate ultrasound images (averaged for days and sides of abdomen), and (c) across 2 days (aver-aged for images and sides).RESULTS: Reliability of assessing muscle thickness was very high across 3 measurements of the same image (intrarater correlation coefficients [ICC(3.1)] were all greater than 0.97), fair to high across 3 images (ICC[3.4] = 0.62-0.82), and fair to high across 2 days (ICC[3.6] = 0.63-0.85). Reliability of measuring the slide of the anterior abdominal fascia was very high across measurements from the same image (ICC[3.1]= 0.98) but very low across images (ICC[3.4] = 0.44) and across 2 days (ICC[3.6] = 0.36).CONCLUSIONS: High reliability of a novice rater was demonstrated for some measurement conditions. Measures of reliability for recapturing the image and repetition across days ranged from low to high. Inconsistencies in the pattern of results suggest that for a novice assessor using RUSI, training should be performed and reliability assessed for each abdominal muscle and measurement condition intended to be used for research and clinical practice. [ABSTRACT FROM AUTHOR]

STUDY DESIGN: Cross-sectional study. OBJECTIVE: To investigate the function of the transversus abdominis (TrA) and internal oblique (10) muscles bilaterally during a simulated weight-bearing task using ultrasound imaging.BACKGROUND: An important aspect of neuromuscular control at the lumbopelvic region is stabilization. Biomechanical models have predicted that activation of transversely oriented muscles, such as the TrA and 10 muscles, can stiffen the sacroiliac joints and actively stabilize the pelvis for weight bearing.METHODS AND MEASURES: Nineteen healthy subjects were positioned in supine lying with their right heel against a footplate linked to a force transducer. Each subject performed a static simulated weight-bearing task of the right lower extremity. Ultrasound imaging was used to assess resultant changes in thickness of the 10 and TrA muscles, as well as the lateral slide of the anterior abdominal fascia on each side of the abdomen alternately. Muscle thickness and slide of the fascia were assessed at standardized force levels (0% and 25% of body weight).RESULTS: Substantial increases (P<.0001) in mean (±SD) thickness of the 10 (18.5% ± 9.7%) and TrA (24.7% ± 17.5%) muscles during the weight-bearing task were measured. Lateral movement (slide) of the anterior abdominal fascia of the TrA muscle also occurred (mean ± SD, 1.3 ± 2.0 mm; P = .014) with weight bearing. Changes in muscle thickness and amount of slide were similar for the left and right side of the abdomen (P>/=.11).CONCLUSION: The findings are consistent with biomechanical models that predicted symmetrical activation of the deep transversely oriented lumbopelvic muscles in healthy subjects in response to a unilateral functional weight-bearing task. Ultrasound imaging as a measurement tool represents a noninvasive method for measuring abdominal muscle function in functional axial loading. [ABSTRACT FROM AUTHOR]