The Effects of Joint-based Pointing Method and Control-Display Gain on Upper Extremity Fatigue in distal pointing

Introduction: Distant pointing is becoming common in both work and domestic environments, and is used for a variety of applications (Bateman, Mandryk, Gutwin, & Xiao, 2013). In order to interact with a computer system in extrapersonal space, users commonly use novel directpointing devices to aim at a specific position that they want to select, and the visual feedback is provided by a cursor to indicate the focus point (Bateman et al., 2013). This kind of pointing method that provides “desk-free” interacting environment to users is called ray-cast pointing (Bateman et al., 2013; Jota, Nacenta, Jorge, Carpendale, & Greenberg, 2010). This technique is based on the idea of Natural User Interface (NUI) analogous to pointing activities in daily life (Francese, Passero, & Tortora, 2012; Kamel Boulos et al., 2011), hence it is easy to learn and use for users who are not familiar with traditional computers (Ortega & Nigay, 2009). Although ray-cast pointing is simple and natural, it still has a few obvious drawbacks, such as difficulties with fatigue (Oh & Stuerzlinger, 2002) and poor accuracy (Kopper, Bowman, Silva, & McMahan, 2010; Myers et al., 2002). Fatigue problems have been considered as much important as performance issues in ray-cast pointing. To provide a comprehensive investigation of the fatigue for muscle groups controlling the various segments of the upper limb, and to establish concrete guidelines for designers of systems that use distant pointing, we carried out a series of experiments that tested and compared three representative joint-based pointing methods. Another important issue of ray-cast pointing is CD gain. Previous studies have reported that there is no clear result governing the effect of CD gain (Accot & Zhai, 2001; Bohan, Thompson, & Samuelson, 2003; Buck, 1980; Gibbs, 1962; Jellinek & Card, 1990; Johnsgard, 1994). Although CD gain has been studied extensively in the context of physical and virtual control devices, unfortunately a definitive picture of the impact of CD gain on fatigue has not been confirmed by these studies. To establish this basic design knowledge, the second purpose of this study was to investigate systemically the effects of CD gain on fatigue.