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Volume 43 Number 7, November/December 2006
Pages 871 — 882

Abstract - Effect of system tilt and seat-to-backrest angles on load sustained by shoulder during wheelchair propulsion

Guillaume Desroches, BSc;1-3* Rachid Aissaoui, PhD;1-3 Daniel Bourbonnais, PhD3

1Laboratoire de Recherche en Imagerie et Orthopédie, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame, Montréal, Québec, Canada; 2Département de Génie de la Production Automatisée, École de Technologie Supérieure, Montréal, Québec, Canada; 3Centre de Recherche Interdisciplinaire en Réadaptation de Montréal, Site Institut de Réadaptation de Montréal, Montréal, Québec, Canada
Abstract — This study determined the effect of system tilt angle (STA) and seat-to-backrest angle (SBA) changes on the load sustained by the shoulder during manual wheelchair propulsion. Fourteen elderly participants (mean +/- standard deviation age 68.2 +/- 5.2 years) were recruited. Combinations of three STAs (0×, 5×, and 10×) and three SBAs (95×, 100×, and 105×) were randomly tested. The initial position of the wheel axle was held constant with respect to the participant's shoulder position in each condition (horizontal: 4 cm forward of shoulder, vertical: 110× to 120× elbow extension). The shoulder load was estimated by the joint moments. The analysis did not reveal any significant differences between shoulder joint moments (average and peak) for the various STA and SBA combinations. Changing the seat angle while keeping the wheel-axle position constant maintained the shoulder load at the same level. Thus, seat angle can be determined with the goals of user comfort and pressure modulation at the seat interface for alleviating pressure ulcers without increasing risk of overuse shoulder injuries.
Key words: injuries, load, manual wheelchair, moments, positioning, propulsion, seat, seat-to-backrest angle, shoulder, system tilt angle.

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