title: Validity and reliability of an IMU-based method to detect APAs prior to gait initiation.
abstract: Anticipatory postural adjustments (APAs) prior to gait initiation have been largely studied in traditional, laboratory settings using force plates under the feet to characterize the displacement of the center of pressure. However clinical trials and clinical practice would benefit from a portable, inexpensive method for characterizing APAs. Therefore, the main objectives of this study were (1) to develop a novel, automatic IMU-based method to detect and characterize APAs during gait initiation and (2) to measure its test-retest reliability. Experiment I was carried out in the laboratory to determine the validity of the IMU-based method in 10 subjects with PD (OFF medication) and 12 control subjects. Experiment II was carried out in the clinic, to determine test-retest reliability of the IMU-based method in a different set of 17 early-to-moderate, treated subjects with PD (tested ON medication) and 17 age-matched control subjects. Results showed that gait initiation characteristics (both APAs and 1st step) detected with our novel method were significantly correlated to the characteristics calculated with a force plate and motion analysis system. The size of APAs measured with either inertial sensors or force plate was significantly smaller in subjects with PD than in control subjects (p<0.05). Test-retest reliability for the gait initiation characteristics measured with inertial sensors was moderate-to-excellent (0.56<ICC<0.82) for both groups. Our findings support the feasibility of automatically characterizing postural preparation and gait initiation with body-worn inertial sensors that would be practical for unsupervised clinical and home settings.
authors.affiliation: Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 Sam Jackson Park Road, Portland, OR, USA. Electronic address: mancinim@ohsu.edu.
authors.forename: Martina
authors.initials: M
authors.lastname: Mancini
authors.affiliation: Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi", University of Bologna, Bologna, Italy. Electronic address: lorenzo.chiari@unibo.it.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Chiari
authors.affiliation: APDM, Inc., Portland, OR, USA. Electronic address: lars@apdm.com.
authors.forename: Lars
authors.initials: L
authors.lastname: Holmstrom
authors.affiliation: Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 Sam Jackson Park Road, Portland, OR, USA. Electronic address: arash.salarian@gmail.com.
authors.forename: Arash
authors.initials: A
authors.lastname: Salarian
authors.affiliation: Department of Neurology, School of Medicine, Oregon Health & Science University, 3181 Sam Jackson Park Road, Portland, OR, USA; APDM, Inc., Portland, OR, USA; Department of Research, Portland VA Medical Center, 3710 SW US Veterans Hospital Rd, Portland, OR, USA. Electronic address: horakf@ohsu.edu.
authors.forename: Fay B
authors.initials: FB
authors.lastname: Horak
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D020233:Gait Disorders, Neurologic / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010300:Parkinson Disease / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D015203:Reproducibility of Results
keywords: Force plates; Gait initiation; Inertial sensors; Parkinson's disease