Changes in Activation of Abdominal Muscles at Selected Angles During Trunk Exercise by Using Ultrasonography

To investigate the changes of activation of the abdominal muscles depending on exercise angles and whether the activation of rectus abdominis differs according to the location, during curl up and leg raise exercises, by measuring the thickness ratio of abdominal muscles using ultrasonography. We examined 30 normal adults without musculoskeletal problems. Muscle thickness was measured in the upper rectus abdominis (URA), lower rectus abdominis (LRA), obliquus externus (EO), obliquus internus (IO), and transversus abdominis (TrA), at pre-determined angles (30°, 60°, 90°) and additionally at the resting angle (0°). Muscle thickness ratio was calculated by dividing the resting (0°) thickness for each angle, and was used as reflection of muscle activity. The muscle thickness ratio was significantly different depending on the angles in URA and LRA. For curl up-URA p=0 (30°90°), p=0.44 (30°90°), respectively, by one-way ANOVA test-and for leg raise-URA p=0 (30°