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Postural adjustments to support surface perturbations during reaching depend upon body–target reference frame

Journal Article


Abstract


  • We investigated whether target position relative to the body modifies the postural adjustments produced when reaching movements are perturbed by unexpected displacements of the support surface. Eleven healthy participants reached to a target located at their midline, acromion height and at 130 % their outstretched arm length. They stood on two force plates mounted on a moveable platform, capable of delivering horizontal forward ramp-and-hold perturbations. Three types of trial were given: reach only (R), perturbations only (P) and reaching movements during which a perturbation was given at a random delay after reach onset (RP). The target could be mounted either on a frame suspended from the ceiling such that it remained world-fixed (exocentric target, RP/X) or at an equivalent position on the moving platform so that it moved with the body (egocentric target, RP/E). Arm and body 3D kinematics and muscle activity from the right tibialis anterior (rTA) and soleus (rSOL) muscles were recorded. Normalised rTA activity was significantly lower in RP than in P trials. Furthermore, long-latency rTA muscle activity was lower in RP/E than in RP/X conditions when perturbations were given during either the arm deceleration phase of reaching. The rSOL muscle activity was lowest for the RP/E (arm deceleration) condition. When balance is perturbed during reaching, the manner in which the target moves relative to the body determines the muscle activity produced in the lower-limb muscles. Furthermore, a target that moves with the body requires a different regulation of muscle activity compared with one that moves independently of the body.

Authors


  •   Hilderley, Alicia J. (external author)
  •   Leonard, Julia A. (external author)
  •   Green, Andrea (external author)
  •   Ouckama, Ryan (external author)
  •   Stapley, Paul J.

Publication Date


  • 2015

Citation


  • Hilderley, A. J., Leonard, J. A., Green, A., Ouckama, R. & Stapley, P. J. (2015). Postural adjustments to support surface perturbations during reaching depend upon body–target reference frame. Experimental Brain Research, 233 (1), 303-316.

Scopus Eid


  • 2-s2.0-84922091811

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/2596

Number Of Pages


  • 13

Start Page


  • 303

End Page


  • 316

Volume


  • 233

Issue


  • 1

Abstract


  • We investigated whether target position relative to the body modifies the postural adjustments produced when reaching movements are perturbed by unexpected displacements of the support surface. Eleven healthy participants reached to a target located at their midline, acromion height and at 130 % their outstretched arm length. They stood on two force plates mounted on a moveable platform, capable of delivering horizontal forward ramp-and-hold perturbations. Three types of trial were given: reach only (R), perturbations only (P) and reaching movements during which a perturbation was given at a random delay after reach onset (RP). The target could be mounted either on a frame suspended from the ceiling such that it remained world-fixed (exocentric target, RP/X) or at an equivalent position on the moving platform so that it moved with the body (egocentric target, RP/E). Arm and body 3D kinematics and muscle activity from the right tibialis anterior (rTA) and soleus (rSOL) muscles were recorded. Normalised rTA activity was significantly lower in RP than in P trials. Furthermore, long-latency rTA muscle activity was lower in RP/E than in RP/X conditions when perturbations were given during either the arm deceleration phase of reaching. The rSOL muscle activity was lowest for the RP/E (arm deceleration) condition. When balance is perturbed during reaching, the manner in which the target moves relative to the body determines the muscle activity produced in the lower-limb muscles. Furthermore, a target that moves with the body requires a different regulation of muscle activity compared with one that moves independently of the body.

Authors


  •   Hilderley, Alicia J. (external author)
  •   Leonard, Julia A. (external author)
  •   Green, Andrea (external author)
  •   Ouckama, Ryan (external author)
  •   Stapley, Paul J.

Publication Date


  • 2015

Citation


  • Hilderley, A. J., Leonard, J. A., Green, A., Ouckama, R. & Stapley, P. J. (2015). Postural adjustments to support surface perturbations during reaching depend upon body–target reference frame. Experimental Brain Research, 233 (1), 303-316.

Scopus Eid


  • 2-s2.0-84922091811

Ro Metadata Url


  • http://ro.uow.edu.au/smhpapers/2596

Number Of Pages


  • 13

Start Page


  • 303

End Page


  • 316

Volume


  • 233

Issue


  • 1