title: Primary and submovement control of aiming in C6 tetraplegics following posterior deltoid transfer.
abstract: BACKGROUND
  Upper limb motor control in fast, goal-directed aiming is altered in tetraplegics following posterior-deltoid musculotendinous transfer. Specifically, movements have similar end-point accuracy but longer duration and lower peak velocity than those of age-matched, neurotypical controls. Here, we examine in detail the interplay between primary movement and submovement phases in five C6 tetraplegic and five control participants.
  
  
  METHODS
  Aiming movements were performed in two directions (20 cm away or toward), with or without vision. Trials that contained a submovement phase (i.e., discontinuity in velocity, acceleration or jerk) were identified. Discrete kinematic variables were then extracted on the primary and submovements phases.
  
  
  RESULTS
  The presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities. Tetraplegics tended to make a smaller amplitude primary movement, which had lower peak velocity and greater spatial variability at peak velocity. This was followed by a larger amplitude and longer duration secondary submovement. Peak velocity of primary movement was not related to submovement incidence. Together, the primary and submovement phases of both groups were equally effective in reducing end-point error.
  
  
  CONCLUSIONS
  C6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming.
authors: Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Tom Reilly Building, Byrom Street, Liverpool L3 3AF, UK. m.a.robinson@ljmu.ac.uk.
authors: Mark A
authors: MA
authors: Robinson
authors: Digby
authors: D
authors: Elliott
authors: Spencer J
authors: SJ
authors: Hayes
authors: Gabor J
authors: GJ
authors: Barton
authors: Simon J
authors: SJ
authors: Bennett
mesh_terms: D000328:Adult; D002574:Cervical Vertebrae; D057645:Deltoid Muscle / Q000637:transplantation*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D011782:Quadriplegia / Q000503:physiopathology* / Q000601:surgery*