title: Proposing a new index to quantify instantaneous symmetry during manual wheelchair propulsion.
abstract: Propelling a manual wheelchair (MWC) is a strenuous task that causes upper limb musculoskeletal disorders (MSD) in a large proportion of MWC users. Although most studies on MWC propulsion biomechanics assume that MWC propulsion is a relatively symmetric task, recent literature suggests that this is the case only when the assessed outcome measures are averaged over long periods of time, and not over short periods (i.e., instantaneously). No method is currently available to assess instantaneous symmetry. In this work, we present the Instantaneous Symmetry Index (ISI), a new method that quantifies how a variable has been instantaneously asymmetric during a selected time period. Thirteen experienced MWC users propelled on different cross slopes of 0%, 2%, 4%, 6% and 8%. As the cross slope is increased, the upper hand produced less propulsive moments and the lower hand produced more propulsive movements. This has been reflected in the ISI, which increased from 0.20 (0% slope) to 0.84 (8% slope) with a Spearman׳s coefficient of 0.90. The ISI has great potential to evaluate the ability of a user to propel symmetrically and synchronously, and will be a relevant measure to include in future studies on the impact of MWC propulsion asymmetry on MSD risk.
authors.affiliation: Department of Physical Activity Science, Faculty of Sciences, Université du Québec à Montréal, Canada; Pathokinesiology Laboratory, Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, Canada. Electronic address: felix@felixchenier.com.
authors.forename: Félix
authors.initials: F
authors.lastname: Chénier
authors.affiliation: Department of Physical Activity Science, Faculty of Sciences, Université du Québec à Montréal, Canada; Pathokinesiology Laboratory, Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, Canada.
authors.forename: Julien
authors.initials: J
authors.lastname: Malbequi
authors.affiliation: Pathokinesiology Laboratory, Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, Canada; Rehabilitation School, Faculty of Medicine, Université de Montréal, Canada.
authors.forename: Dany H
authors.initials: DH
authors.lastname: Gagnon
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D013119:Spinal Cord Injuries; D034941:Upper Extremity / Q000502:physiology*; D014910:Wheelchairs; D055815:Young Adult
keywords: Biomechanics; Rehabilitation; Symmetry; Upper extremity; Wheelchairs