title: Postural control strategies related to anticipatory perturbation and quick perturbation in adolescent idiopathic scoliosis.
abstract: METHODS
  Cross-sectional study.
  
  
  OBJECTIVE
  To investigate the automatic balance correction related to anticipatory perturbation (AP) and quick backward perturbation in adolescent idiopathic scoliosis (AIS).
  
  
  BACKGROUND
  Most previous studies on AIS patients focused on posture sway and lacked analysis of muscle activated patterns in dynamic standing control.
  
  
  METHODS
  Thirty-two AIS patients and 23 age-matched normal subjects received perturbation balance tests on an unstable platform. The tilting angle of the platform and the muscle activity of the bilateral lumbar multifidi, gluteus medii, and gastrocnemii muscles were recorded. Electromyographic (EMG) amplitude, onset latencies, and duration were calculated with software accompanied with machine.
  
  
  RESULTS
  The AIS group had less posture tilting but higher muscle activities than normal subjects under both perturbation conditions (P < 0.05). Under the AP test, AIS showed earlier onset and prolonged activation of left multifidus and right gastrocnemius compared with normal subjects (P < 0.05). The latency of the multifidus on the lumbar convex side occurred earlier than on the concave side. However, the asymmetric onset timing of the gastrocnemius was the opposite of the multifidi in the AIS group (P < 0.05). In contrast to the AP condition, bilateral leg and trunk muscles activated at similar latencies and durations in the AIS group (P < 0.05). Under the quick backward perturbation test, the control group had longer active duration of right multifidus and bilateral gastrocnemii than AIS to cope with larger platform tilting. In addition, asymmetric onset of gluteus medii and duration of multifidi was observed in the control group (P < 0.05).
  
  
  CONCLUSIONS
  There were significant differences in posture control patterns between AIS and normal subjects. AIS subjects have asymmetric habitual muscle activities for AP, whereas when coping with sudden balance threats, they react with synchronized recruitment of bilateral postural muscles.
authors.affiliation: Department of Physical Therapy, Medicine, and Nursing College, Hungkuang University, Taichung, Taiwan. kfc@sunrise.hk.edu.tw
authors.forename: Fang-Chuan
authors.initials: FC
authors.lastname: Kuo
authors.forename: Chang-Zern
authors.initials: CZ
authors.lastname: Hong
authors.forename: Chung-Liang
authors.initials: CL
authors.lastname: Lai
authors.forename: Shih-Hsin
authors.initials: SH
authors.lastname: Tan
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D002648:Child; D003430:Cross-Sectional Studies; D004576:Electromyography; D005684:Gait / Q000502:physiology*; D006801:Humans; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D012600:Scoliosis / Q000503:physiopathology*