title: Trunk-acceleration based assessment of gait parameters in older persons: a comparison of reliability and validity of four inverted pendulum based estimations.
abstract: Inverted pendulum (IP) models of human walking allow for wearable motion-sensor based estimations of spatio-temporal gait parameters during unconstrained walking in daily-life conditions. At present it is unclear to what extent different IP based estimations yield different results, and reliability and validity have not been investigated in older persons without a specific medical condition. The aim of this study was to compare reliability and validity of four different IP based estimations of mean step length in independent-living older persons. Participants were assessed twice and walked at different speeds while wearing a tri-axial accelerometer at the lower back. For all step-length estimators, test-retest intra-class correlations approached or were above 0.90. Intra-class correlations with reference step length were above 0.92 with a mean error of 0.0 cm when (1) multiplying the estimated center-of-mass displacement during a step by an individual correction factor in a simple IP model, or (2) adding an individual constant for bipedal stance displacement to the estimated displacement during single stance in a 2-phase IP model. When applying generic corrections or constants in all subjects (i.e. multiplication by 1.25, or adding 75% of foot length), correlations were above 0.75 with a mean error of respectively 2.0 and 1.2 cm. Although the results indicate that an individual adjustment of the IP models provides better estimations of mean step length, the ease of a generic adjustment can be favored when merely evaluating intra-individual differences. Further studies should determine the validity of these IP based estimations for assessing gait in daily life.
authors.affiliation: Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. Electronic address: a.zijlstra@umcg.nl.
authors.forename: Agnes
authors.initials: A
authors.lastname: Zijlstra
authors.forename: Wiebren
authors.initials: W
authors.lastname: Zijlstra
mesh_terms: D000054:Acceleration; D061725:Accelerometry; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008962:Models, Theoretical; D015203:Reproducibility of Results; D060726:Torso / Q000502:physiology*
keywords: Accelerometry; Independent living; Inverted pendulum model; Older persons; Spatio-temporal gait parameters