title: Postural strategies assessed with inertial sensors in healthy and parkinsonian subjects.
abstract: The present study introduces a novel instrumented method to characterize postural movement strategies to maintain balance during stance (ankle and hip strategy), by means of inertial sensors, positioned on the legs and on the trunk. We evaluated postural strategies in subjects with 2 types of Parkinsonism: idiopathic Parkinson's disease (PD) and Progressive Supranuclear Palsy (PSP), and in age-matched control subjects standing under perturbed conditions implemented by the Sensory Organization Test (SOT). Coordination between the upper and lower segments of the body during postural sway was measured using a covariance index over time, by a sliding-window algorithm. Afterwards, a postural strategy index was computed. We also measured the amount of postural sway, as adjunctive information to characterize balance, by the root mean square of the horizontal trunk acceleration signal (RMS).
  
  
  RESULTS
  showed that control subjects were able to change their postural strategy, whilst PSP and PD subjects persisted in use of an ankle strategy in all conditions. PD subjects had RMS values similar to control subjects even without changing postural strategy appropriately, whereas PSP subjects showed much larger RMS values than controls, resulting in several falls during the most challenging SOT conditions (5 and 6). Results are in accordance with the corresponding clinical literature describing postural behavior in the same kind of subjects. The proposed strategy index, based on the use of inertial sensors on the upper and lower body segments, is a promising and unobtrusive tool to characterize postural strategies performed to attain balance.
authors.affiliation: Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy. Electronic address: chiara.baston@unibo.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Baston
authors.affiliation: Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, USA(1).
authors.forename: Martina
authors.initials: M
authors.lastname: Mancini
authors.affiliation: Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, USA(1).
authors.forename: Bernadette
authors.initials: B
authors.lastname: Schoneburg
authors.affiliation: Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 Sam Jackson Park Road, Portland, OR 97239-3098, USA(1).
authors.forename: Fay
authors.initials: F
authors.lastname: Horak
authors.affiliation: Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Rocchi
mesh_terms: D000054:Acceleration; D061725:Accelerometry / Q000295:instrumentation; D000368:Aged; D000842:Ankle / Q000503:physiopathology; D001259:Ataxia / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D056228:Feedback, Sensory / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D008991:Monitoring, Physiologic / Q000295:instrumentation; D009068:Movement / Q000502:physiology; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D012678:Sensation Disorders / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D013494:Supranuclear Palsy, Progressive / Q000150:complications / Q000503:physiopathology*; D060726:Torso / Q000503:physiopathology
keywords: Covariance analysis; Dynamic posture; Parkinson's disease; Progressive Supranuclear Palsy; Sensory Organization Test