title: Relationship Between the Kinematics of the Trunk and Lower Extremity and Performance on the Y-Balance Test.
abstract: BACKGROUND
  The lower quarter Y-balance test (YBT-LQ) has been recommended as a measure of dynamic postural control in the clinical setting; however, information about the relationship between performance on the YBT-LQ and joint kinematics is limited. Thus, the kinematic predictors responsible for performance on the YBT-LQ need to be identified for accurate evaluation of dynamic postural control.
  
  
  OBJECTIVE
  To identify the kinematic predictors that best explain variance in performance on the YBT-LQ.
  
  
  METHODS
  Cross-sectional design.
  
  
  METHODS
  University motion analysis laboratory.
  
  
  METHODS
  Thirty physically active participants.
  
  
  METHODS
  All participants performed the YBT-LQ. The kinematics of the trunk and lower extremity at maximal reach in each direction of the YBT-LQ were monitored using a 3-dimensional motion analysis system.
  
  
  METHODS
  The correlations between reach distance and joint kinematics were assessed using Pearson's correlation coefficient, and the best predictors of performance on the YBT-LQ were determined using a stepwise multiple regression analysis.
  
  
  RESULTS
  Ankle dorsiflexion was the best single predictor of normalized reach in the anterior direction of the YBT-LQ (r(2) = 0.50), and the combination of ankle dorsiflexion and trunk extension explained 65% of the variance in the anterior normalized reach. Hip flexion was the best single predictor of posteromedial (r(2) = 0.60) and posterolateral (r(2) = 0.71) normalized reaches of the YBT-LQ. The combination of hip flexion and ipsilateral trunk bending and the combination of hip flexion and contralateral trunk bending accounted for 69% and 80% of the variance in the posteromedial and posterolateral normalized reaches of the YBT-LQ, respectively.
  
  
  CONCLUSIONS
  These findings provide useful information on the relative contribution of joint kinematics to performance on the YBT-LQ when evaluating dynamic postural control.
authors.affiliation: Department of Physical Therapy, Graduate School, INJE University, Gimhae, South Korea.
authors.forename: Min-Hyeok
authors.initials: MH
authors.lastname: Kang
authors.affiliation: Department of Physical Therapy, BAEKSEOK University, Cheonan, South Korea.
authors.forename: Gyoung-Mo
authors.initials: GM
authors.lastname: Kim
authors.affiliation: Laboratory of Kinetic Ergocise Based on Movement Analysis, Department of Physical Therapy, YONSEI University, Wonju, Gangwon-do, South Korea.
authors.forename: Oh-Yun
authors.initials: OY
authors.lastname: Kwon
authors.affiliation: Department of Physical Therapy, JOONGBU University, Chubu-myeon, Geumsan-gun, Chungcheongnam-do, South Korea.
authors.forename: Jong-Hyuk
authors.initials: JH
authors.lastname: Weon
authors.affiliation: Department of Physical Therapy, College of Biomedical Science and Engineering, INJE University 607 Obang-dong, Gimhae-si, Gyeongsangnam-do, South Korea, 621-749.
authors.forename: Jae-Seop
authors.initials: JS
authors.lastname: Oh
authors.affiliation: Department of Physical Therapy, INJE University, Gimhae, South Korea.
authors.forename: Duk-Hyun
authors.initials: DH
authors.lastname: An
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D060726:Torso / Q000502:physiology*; D055815:Young Adult