ABSTRACT
This study investigated the changes in muscle thickness of transversus abdominis (TrA) during trunk muscle training. The subjects comprised 30 young men (average age 20.1 SD1.6 years) without low back pain. The muscle thickness of the upper region of TrA, middle region of TrA and lower region of TrA were measured by B-mode ultrasound. Muscle thickness were measured at rest and during the following 5 exercises; abdominal drawing, curl up, trunk ipsilateral rotation, trunk contralateral rotation and both straight leg raise in supine. There were no significant differences in the muscle thickness of the upper region of TrA between resting condition and all exercises. Muscle thickness during drawing, curl up and ipsilateral rotation were significantly greater than that at rest in middle region of TrA, and the rate of change in muscle thickness was the largest for drawing. Muscle thickness during drawing, curl up and ipsilateral rotation were significantly greater than that at rest in the lower region of TrA, and the rate of change in muscle thickness was the largest for ipsilateral rotation. These results suggested that the changes in muscle thickness of TrA during trunk muscle training showed different patterns depending on the region of TrA.