Postural inflexibility in parkinsonian subjects

F. B. Horak, J. G. Nutt, L. M. Nashner

Research output: Contribution to journalArticlepeer-review

379 Scopus citations


In order to identify the types of postural deficits seen in parkinsonian patients with postural instability, we compared the performance of parkinsonian subjects with young and old control subjects in 3 aspects of postural control: (1) the use of sensory information for postural orientation, (2) the coordination of postural movement patterns in response to surface displacements, and (3) the flexible modification of postural response patterns to changes in support conditions. Parkinsonian subjects had very small sway, even under altered sensory conditions. Postural response latencies to displacements were also normal. Postural instability was associated with abnormal patterns of postural responses including excessive antagonist activity and inflexibility in adapting to changing support conditions. Some parkinsonian subjects appeared to have difficulty sequencing motor programs for postural correction. The parkinsonian subjects appeared stiffer since the rate-of-change of sway in response to displacements was reduced. Levodopa improved postural coordination but not the flexible adaptation to changing support conditions.

Original languageEnglish (US)
Pages (from-to)46-58
Number of pages13
JournalJournal of the neurological sciences
Issue number1
StatePublished - Aug 1992


  • EMG
  • Levodopa
  • Parkinsonism
  • Posture
  • Sensory information

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology


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