The relationship between intermittent limit cycles and postural instability associated with Parkinson's disease

James R. Chagdes, Jessica E. Huber, Meredith Saletta, Meghan Darling-White, Arvind Raman, Shirley Rietdyk, Howard N. Zelaznik, Jeffrey M. Haddad

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Background: Many disease-specific factors such as muscular weakness, increased muscle stiffness, varying postural strategies, and changes in postural reflexes have been shown to lead to postural instability and fall risk in people with Parkinson's disease (PD). Recently, analytical techniques, inspired by the dynamical systems perspective on movement control and coordination, have been used to examine the mechanisms underlying the dynamics of postural declines and the emergence of postural instabilities in people with PD. Methods: A wavelet-based technique was used to identify limit cycle oscillations (LCOs) in the anterior-posterior (AP) postural sway of people with mild PD (n = 10) compared to age-matched controls (n = 10). Participants stood on a foam and on a rigid surface while completing a dual task (speaking). Results: There was no significant difference in the root mean square of center of pressure between groups. Three out of 10 participants with PD demonstrated LCOs on the foam surface, while none in the control group demonstrated LCOs. An inverted pendulum model of bipedal stance was used to demonstrate that LCOs occur due to disease-specific changes associated with PD: time-delay and neuromuscular feedback gain. Conclusion: Overall, the LCO analysis and mathematical model appear to capture the subtle postural instabilities associated with mild PD. In addition, these findings provide insights into the mechanisms that lead to the emergence of unstable posture in patients with PD.

Original languageEnglish (US)
Pages (from-to)14-24
Number of pages11
JournalJournal of Sport and Health Science
Issue number1
StatePublished - Mar 1 2016


  • Balance
  • Limit cycle
  • Parkinson's disease
  • Posture
  • Wavelets

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


Dive into the research topics of 'The relationship between intermittent limit cycles and postural instability associated with Parkinson's disease'. Together they form a unique fingerprint.

Cite this