title: Changes in Activation of Abdominal Muscles at Selected Angles During Trunk Exercise by Using Ultrasonography.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  The muscle thickness ratio was significantly different depending on the angles in URA and LRA. For curl up-URA p=0 (30°<60°), p=0 (60°>90°), p=0.44 (30°<90°) and LRA p=0.01 (30°<60°), p=0 (60°>90°), p=0.44 (30°>90°), respectively, by one-way ANOVA test-and for leg raise-URA p=0 (30°<60°), p=0 (60°<90°), p=0 (30°<90°) and LRA p=0.01 (30°<60°), p=0 (60°<90°), p=0 (30°<90°), respectively, by one-way ANOVA test-exercises, but not in the lateral abdominal muscles (EO, IO, and TrA). Also, there was no significant difference in the muscle thickness ratio of URA and LRA during both exercises. In the aspect of muscle activity, there was significant difference in the activation of RA muscle by selected angles, but not according to location during both exercises.
  
  
  CONCLUSIONS
  According to this study, exercise angle is thought to be an important contributing factor for strengthening of RA muscle; however, both the exercises are thought to have no property of strengthening RA muscle selectively based on the location.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Hyun-Dong
authors.initials: HD
authors.lastname: Kim
authors.affiliation: Department of Physical Medicine and Rehabilitation, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Dong-Min
authors.initials: DM
authors.lastname: Jeon
authors.affiliation: Department of Physical Medicine and Rehabilitation, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Bae
authors.affiliation: Department of Physical Medicine and Rehabilitation, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Jong-Gil
authors.initials: JG
authors.lastname: Kim
authors.affiliation: Department of Physical Medicine and Rehabilitation, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Nami
authors.initials: N
authors.lastname: Han
authors.affiliation: Department of Physical Medicine and Rehabilitation, Inje University Busan Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Mi-Ja
authors.initials: MJ
authors.lastname: Eom
keywords: Abdominal muscles; Exercise; Ultrasonography