M-mode ultrasound: a reliable measure of transversus abdominis thickness?

Objective. The purpose of this study was to establish a reliable method for measuring transversus abdominis thickness in asymptomatic human subjects in supine lying, standing and walking. Design and methods. This was a single operator reliability study using ultrasound imaging to measure 22 subjects on three separate occasions. A purpose built high-density foam reinforced belt was used to house and position the transducer over the mid-point of the transversus abdominis. Each subject was imaged in supine, standing, and treadmill walking at 3 kph. Intraclass correlation coefficients and standard error of measurement analysis were used to measure the data. Results. The correlation coefficient data analysis resulted in intraclass correlation coefficients of 0.94 (standard error of measurement 0.35) in supine lying, 0.88 (0.66) in standing and 0.88 (0.56) in walking. Conclusion. The method described is a reliable tool for measuring changes in thickness of transversus abdominis in supine lying, standing and walking. Relevance. This procedure has the potential to detect dysfunctional changes in abdominal muscle activity for patients with low back pain in a functional setting.