title: Arm-trunk coordination for beyond-the-reach movements in adults with stroke.
abstract: BACKGROUND
  By involving additional degrees of freedom, the nervous system may preserve hand trajectories when making pointing movements with or without trunk displacement. Previous studies indicate that the potential contribution of trunk movement to hand displacement for movements made within arm reach is neutralized by appropriate compensatory shoulder and elbow rotations. For beyond-the-reach movements, compensatory coordination is attenuated after the hand peak velocity, allowing trunk movement to contribute to hand displacement.
  
  
  OBJECTIVE
  To investigate if the timing and spatial coordination of arm and trunk movements during beyond-the-reach movements is preserved in stroke.
  
  
  METHODS
  Eleven healthy control subjects and 11 individuals with mild-to-moderate chronic unilateral hemiparesis participated. Arm and trunk kinematics during 60 target reaches to an ipsilaterally placed target were recorded. In 30% of randomly chosen trials, trunk movement was unexpectedly prevented (blocked-trunk trials) by an electromagnetic device, resulting in divergence of the hand trajectory from that in free-trunk trials. Hand trajectories and elbow-shoulder interjoint coordination were compared between trials.
  
  
  RESULTS
  In stroke participants, hand trajectory divergence occurred at a shorter movement extent and interjoint coordination patterns diverged at a relatively greater distance compared to controls. Thus, arm movements in stroke participants only partially compensated trunk displacement resulting in the trunk movement contributing to arm movement earlier and to a larger extent during reaching.
  
  
  CONCLUSIONS
  Individuals with mild-to-moderate stroke have deficits in timing and spatial coordination of arm and trunk movements during different parts of a reaching movement. This deficit may be targeted in therapy to improve upper limb function.
authors.affiliation: 1McGill University, Montreal, Quebec, Canada.
authors.forename: Tahir
authors.initials: T
authors.lastname: Shaikh
authors.forename: Valerie
authors.initials: V
authors.lastname: Goussev
authors.forename: Anatol G
authors.initials: AG
authors.lastname: Feldman
authors.forename: Mindy F
authors.initials: MF
authors.lastname: Levin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001132:Arm / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D002908:Chronic Disease; D004550:Elbow / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010291:Paresis / Q000209:etiology / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000502:physiology*; D012782:Shoulder / Q000503:physiopathology; D020521:Stroke / Q000150:complications / Q000503:physiopathology*; D013997:Time Factors; D060726:Torso / Q000503:physiopathology*
keywords: arm movement; hemiplegia; interjoint coordination; motor control; referent configuration hypothesis