title: Squat test performance and execution in children with and without cerebral palsy.
abstract: BACKGROUND
  Knowledge on lower extremity strength is imperative to informed decision making for children with cerebral palsy (CP) with mobility problems. However, a functional and clinically feasible test is not available. We aimed to determine whether the squat test is suitable for this purpose by investigating test performance and execution in children with cerebral palsy and typically developing (TD) peers.
  
  
  METHODS
  Squat test performance, defined by the number of two-legged squats until fatigue (max 20), was assessed in twenty children with bilateral CP (6-19years; gross motor function classification system I-III) and sixteen TD children (7-16years). Muscle fatigue was assessed from changes in electromyography (EMG). Joint range-of-motion and net torque were calculated for each single squat, to investigate differences between groups and between the 2nd and last squat.
  
  
  RESULTS
  Fifteen children with CP performed <20 squats (median=13, IQR=7-19), while all TD children performed the maximum of 20 squats. Median EMG frequency decreased and amplitude increased in mm. quadriceps of both groups. Ankle and knee range-of-motion were reduced in children with CP during a single squat by 10 to 15°. No differences between 2nd and last squat were observed, except for knee range-of-motion which increased in TD children and decreased in children with CP.
  
  
  CONCLUSIONS
  Squat test performance was reduced in children with CP, especially in those with more severe CP. Muscle fatigue was present in both children with CP and TD peers, confirming that endurance of the lower extremity was tested. Minor execution differences between groups suggest that standardized execution is important to avoid compensation strategies. It is concluded that the squat test is feasible to test lower extremity strength in children with CP in a clinically meaningful way. Further clinimetric evaluation is needed before clinical implementation.
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands; Heliomare Rehabilitation, Research and Development, Wijk aan Zee, The Netherlands. Electronic address: m.eken@vumc.nl.
authors.forename: M M
authors.initials: MM
authors.lastname: Eken
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Harlaar
authors.affiliation: Department of Rehabilitation Medicine, MOVE Research Institute Amsterdam, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Dallmeijer
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: de Waard
authors.affiliation: Heliomare Rehabilitation, Research and Development, Wijk aan Zee, The Netherlands; Coronel Institute of Occupational Health, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: C A M
authors.initials: CA
authors.lastname: van Bennekom
authors.affiliation: Heliomare Rehabilitation, Research and Development, Wijk aan Zee, The Netherlands; Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Houdijk
mesh_terms: D000293:Adolescent; D000843:Ankle Joint / Q000502:physiology / Q000503:physiopathology; D016022:Case-Control Studies; D002547:Cerebral Palsy / Q000503:physiopathology*; D002648:Child; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology / Q000503:physiopathology; D035002:Lower Extremity / Q000502:physiology / Q000503:physiopathology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000502:physiology / Q000503:physiopathology; D016059:Range of Motion, Articular / Q000502:physiology; D019415:Torque; D055815:Young Adult