title: Lower-limb kinematics of single-leg squat performance in young adults.
abstract: OBJECTIVE
  To determine the kinematic parameters that characterize good and poor single-leg squat (SLS) performance.
  
  
  METHODS
  A total of 22 healthy young adults free from musculoskeletal impairment were recruited for testing. For each SLS, both two-dimensional video and three-dimensional motion analysis data were collected. Pelvis, hip, and knee angles were calculated using a reliable and validated lower-limb (LL) biomechanical model. Two-dimensional video clips of SLSs were blindly assessed in random order by eight musculoskeletal physiotherapists using a 10-point ordinal scale. To facilitate between-group comparisons, SLS performances were stratified by tertiles corresponding to poor, intermediate, and good SLS performance.
  
  
  RESULTS
  Mean ratings of SLS performance assessed by physiotherapists were 8.3 (SD 0.5), 6.8 (SD 0.7), and 4.0 (SD 0.8) for good, intermediate, and poor squats, respectively. Three-dimensional analysis revealed that people whose SLS performance was assessed as poor exhibited increased hip adduction, reduced knee flexion, and increased medio-lateral displacement of the knee joint centre compared to those whose SLS performance was assessed as good (p≤0.05).
  
  
  CONCLUSIONS
  Overall, poor SLS performance is characterized by inadequate knee flexion and excessive frontal plane motion of the knee and hip. Future investigations of SLS performance should consider standardizing knee flexion angle to illuminate other influential kinematic parameters.
authors.affiliation: Centre for Musculoskeletal Research and School of Rehabilitation Sciences, Griffith Health Institute, Griffith University.
authors.forename: Sean A
authors.initials: SA
authors.lastname: Horan
authors.affiliation: Centre for Musculoskeletal Research and School of Rehabilitation Sciences, Griffith Health Institute, Griffith University.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Watson
authors.affiliation: Centre for Musculoskeletal Research and School of Rehabilitation Sciences, Griffith Health Institute, Griffith University ; Queensland Children's Gait Laboratory, Royal Children's Hospital, Queensland Health, Australia.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Carty
authors.affiliation: Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology, University Medical Centre Göttingen, Georg-August University, Göttingen, Germany.
authors.forename: Massimo
authors.initials: M
authors.lastname: Sartori
authors.affiliation: Centre for Musculoskeletal Research and School of Rehabilitation Sciences, Griffith Health Institute, Griffith University.
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Weeks
keywords: kinematics; knee joint; leg injuries; musculoskeletal physiological phonomena