title: Sensitivity of local dynamic stability of over-ground walking to balance impairment due to galvanic vestibular stimulation.
abstract: Impaired balance control during gait can be detected by local dynamic stability measures. For clinical applications, the use of a treadmill may be limiting. Therefore, the aim of this study was to test sensitivity of these stability measures collected during short episodes of over-ground walking by comparing normal to impaired balance control. Galvanic vestibular stimulation (GVS) was used to impair balance control in 12 healthy adults, while walking up and down a 10 m hallway. Trunk kinematics, collected by an inertial sensor, were divided into episodes of one stroll along the hallway. Local dynamic stability was quantified using short-term Lyapunov exponents (λ(s)), and subjected to a bootstrap analysis to determine the effects of number of episodes analysed on precision and sensitivity of the measure. λ(s) increased from 0.50 ± 0.06 to 0.56 ± 0.08 (p = 0.0045) when walking with GVS. With increasing number of episodes, coefficients of variation decreased from 10 ± 1.3% to 5 ± 0.7% and the number of p values >0.05 from 42 to 3.5%, indicating that both precision of estimates of λ(s) and sensitivity to the effect of GVS increased. λ(s) calculated over multiple episodes of over-ground walking appears to be a suitable measure to calculate local dynamic stability on group level.
authors.affiliation: Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands.
authors.forename: Lizeth H
authors.initials: LH
authors.lastname: Sloot
authors.forename: Kimberley S
authors.initials: KS
authors.lastname: van Schooten
authors.forename: Sjoerd M
authors.initials: SM
authors.lastname: Bruijn
authors.forename: Herman
authors.initials: H
authors.lastname: Kingma
authors.forename: Mirjam
authors.initials: M
authors.lastname: Pijnappels
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieën
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004558:Electric Stimulation; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008954:Models, Biological; D004856:Postural Balance; D014722:Vestibule, Labyrinth / Q000503:physiopathology*; D016138:Walking