The influence of handrim design on the contact forces on hands' surface: A preliminary study Fausto Orsi Medola a, b, * , Danilo Corr ^ ea Silva b , Carlos Alberto Fortulan c , Val  eria Meirelles Carril Elui d, e , Luis Carlos Paschoarelli a, b a Department of Design, Faculty of Architecture, Arts and Communication, UNESP-Univ Estadual Paulista, Bauru, SP, Brazil b Programme of Post Graduation in Design, UNESP-Univ Estadual Paulista, Bauru, SP, Brazil c Department of Mechanical Engineering, Sao Carlos School of Engineering, University of Sao Paulo, SP, Brazil d Department of Neuroscience and Behavioral Sciences, University of Sao Paulo, Ribeirao Preto, SP, Brazil e Programme of Post Graduation Interunits in Bioengineering, University of Sao Paulo, Sao Carlos, SP, Brazil article info Article history: Received 28 January 2014 Received in revised form 12 July 2014 Accepted 21 September 2014 Available online 8 October 2014 Keywords: Wheelchairs Hand Manual propulsion Human engineering Rehabilitation abstract This study is aimed at investigating how contact forces are distributed over the hand's surface during manual wheelchair propulsion with two different designs of handrim. Twenty able-bodied subjects performed a wheelchair propulsion protocol comprising five consecutive pushes: start-up, straight motion and braking. The protocol was repeated twice, each time with a handrim type: the standard round metallic tube handrims, and a prototype of an ergonomic handrim. During all the tests, contact forces over the users' hand surfaces were measured through a pair of gloves instrumented with ten force sensors each. The average values of each sensor were used to compare both handrims, and statistical tests were used to verify significant differences. The results indicate that the handrim design influences the magnitude of contact forces on hands' surface. There was a reduction in the magnitude of the contact forces in both regions e metacarpals and distal phalanges e during the three propulsion phases with the use of the ergonomic handrim. Among all ten sensors, the distal phalange of the third finger registered the greater forces during start-up, forward motion and braking. The reduction on the contact forces with the use of the ergonomic handrim is possible due to the increased surface and the anatomical shape. Improving handrim design can contribute the ergonomics of manual propulsion, thus benefiting users' comfort and safety in wheelchair mobility. Relevance to industry: This study contributes to the knowledge of the ergonomics of manual wheelchair propulsion, with the main focus on the hand-handrim interface. Thus, it can benefit designers and manufacturers in developing handrims with ergonomics features, as well as improve the users' comfort and safety during manual wheelchair usage. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Manual propulsion, the main means of wheelchair ambulation, exposes the upper limbs to high loads and repetitive task, and as a consequence there is an increased risk of overuse injuries (Gellman et al., 1988; Curtis et al., 1999; Subbarao et al., 1994). Since wheel- chair users rely on their upper limbs for mobility and most of the activities of daily living, pain and upper limb injuries can impact functionality, independence, and quality of life (Finnerup et al., 2001; Jensen et al., 2005; Ehde et al., 2003; Alm et al., 2008). Therefore, reducing workload and improving the comfort of the users' hands during propulsion is an important goal for both rehabilitation practice and engineering. As the interface through which the user controls a manual wheelchair, the handrim plays a key role on the manual propulsion technique. van der Woude et al. (2003) highlighted the need of a stable coupling between the hands and the handrims on both propulsion and navigation of the wheelchair. Because wheelchair propulsion requires the hands to hold and push a rotating handrim quickly, the standard handrim d a round metallic tube located on the outer side of the wheel d have no ergonomic features, requires a pinch grip and was not designed for variations in upper limb * Corresponding author. Department of Design, Faculty of Architecture, Arts and Communication, UNESP-Univ Estadual Paulista. Av Eng Luiz Edmundo Carrijo Coube,14-01, Bauru, SP 17033-360, Brazil. Tel.: þ55 14 3103 6000 6062. E-mail addresses: fausto.medola@faac.unesp.br, fmedola@yahoo.com.br (F.O. Medola). Contents lists available at ScienceDirect International Journal of Industrial Ergonomics journal homepage: www.elsevier.com/locate/ergon http://dx.doi.org/10.1016/j.ergon.2014.09.005 0169-8141/© 2014 Elsevier B.V. All rights reserved. International Journal of Industrial Ergonomics 44 (2014) 851e856