title: The validity of assessing temporal events, sub-phases and trunk kinematics of the sit-to-walk movement in older adults using a single inertial sensor.
abstract: The aim of this study was to develop a method to identify temporal events, sub-phases and trunk kinematics of the sit-to-walk (STW) using a single inertial sensor (IS) worn at the lower back and to determine the validity of this method. Twenty-seven healthy older adults performed a STW movement, which started from sitting in a chair and included walking 3m. Participants׳ movements were recorded with the IS, a reference measurement system consisting of an optical motion capture system (3 markers on the IS and one on each foot) and on-off switches located in the seat of the chair. Using the data from the IS and the reference measurement systems, the following signals and variables were calculated and compared: 3D IS motion (accelerations, velocities, displacements and angles), temporal events (start of trunk movement, seat-off, end of trunk flexion phase, end of trunk rising phase and gait initiation) and trunk kinematics (flexion range, maximum flexion velocity, maximum forward velocity and forward velocity during seat-off and at first heel-strike and maximum vertical velocity and vertical velocity at first heel-strike). For most variables acceptable differences (RMSE<10%) were found between IS and reference measurement systems, except for sideways displacements and non-sagittal plane rotations. Furthermore, good results were found for temporal event detection, with ICC values for all variables being 0.988 or higher. With exception of the vertical velocity at heel-strike agreement for trunk kinematics was high, with ICC values being 0.867 or higher.
authors.affiliation: McRoberts, Raamweg 43, 2596 HN The Hague, The Netherlands. Electronic address: s.walgaard@mcroberts.nl.
authors.forename: Stefan
authors.initials: S
authors.lastname: Walgaard
authors.affiliation: Research Institute MOVE, Department of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
authors.forename: Gert S
authors.initials: GS
authors.lastname: Faber
authors.affiliation: McRoberts, Raamweg 43, 2596 HN The Hague, The Netherlands.
authors.forename: Rob C
authors.initials: RC
authors.lastname: van Lummel
authors.affiliation: Research Institute MOVE, Department of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
authors.affiliation: Research Institute MOVE, Department of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands.
authors.forename: Idsart
authors.initials: I
authors.lastname: Kingma
mesh_terms: D000054:Acceleration; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D005528:Foot / Q000502:physiology; D005684:Gait / Q000502:physiology; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology*; D060726:Torso / Q000502:physiology*; D016138:Walking / Q000502:physiology*
keywords: 3D motion validity; Accelerometers; Gyroscopes; Inertial sensor; Sit-to-walk