Analysis of postural perturbation responses.
People with cerebellar ataxia lack lower limb coordination and dissipate sway motion slowly and inefficiently after a posture perturbation. We report a practical and low-cost "human resonance frequency test" for both laboratory and clinical use to quantify progress in balance and cerebellar rehabilitation. We assumed that the center-of-pressure (COP) oscillation rate of decay following a standing posture perturbation is directly related to resonance frequency; a more rapidly dissipating COP oscillation about the position of equilibrium indicates, by definition, more efficient postural control. We hypothesized that following successful physical rehabilitation, people with cerebellar degeneration will have a faster rate of decay of the COP response to an external perturbation. Because the COP is modulated by a synergy of trunk and lower limb motion strategies, COP decay rate may be a useful measure of lower limb coordination in people with cerebellar ataxia. The method was applied to three subjects with cerebellar ataxia before and after rehabilitation; there was good agreement between the calculated COP decay rate and conventionally used gait stability parameters providing pilot data for this simple approach.
Krebs
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Massachusetts General Hospital, Biomotion Laboratory, MGH Institute of Health Professions and Harvard Medical School, Boston 02114-4719, USA. krebs@helix.mgh.harvard.edu
McGibbon
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CA
Goldvasser
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D000222:Adaptation, Physiological / Q000502:physiology; D002524:Cerebellar Ataxia / Q000503:physiopathology* / Q000534:rehabilitation*; D005684:Gait / Q000502:physiology; D006801:Humans; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010812:Physical Stimulation; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted