title: Ball catching in children with developmental coordination disorder: control of degrees of freedom.
abstract: This study investigated two-handed catching in eight children (four males, four females) aged 7 to 8 years (mean 7y 4mo [SD 3mo]) with developmental coordination disorder (DCD) and their age-matched controls (AMCs). Kinematic data were collected to examine Bernstein's (1967) notion of freezing and releasing degrees of freedom (DF). Participants were asked to catch a ball 30 times, delivered in three blocks of 10 trials. Video analysis showed that children with DCD caught significantly fewer balls than their AMCs (p< or =0.001) counterparts. Kinematic analyses showed that children with DCD exhibited smaller ranges of motion and less variable angular excursions of the elbow joints than their AMCs, and that their elbows are more rigidly coupled (p< or =0.001). These data suggest that children with DCD rigidly fix and couple their limbs to reduce the number of DF actively involved in the task.
authors.affiliation: Centre for Sport and Exercise Sciences, University of Leeds, UK. a.utley@leeds.ac.uk
authors.forename: Andrea
authors.initials: A
authors.lastname: Utley
authors.forename: Bert
authors.initials: B
authors.lastname: Steenbergen
authors.forename: Sarah Louise
authors.initials: SL
authors.lastname: Astill
mesh_terms: D001696:Biomechanical Phenomena; D002648:Child; D005260:Female; D018737:Hand Strength; D006801:Humans; D008297:Male; D019957:Motor Skills Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology; D013177:Sports; D014743:Videotape Recording