Saskia Baltrusch

59 Chapter 3 The perceived task difficulty increased in many of the tasks when wearing the exoskeleton, and decreased in one of the tasks that were expected to be supported by the device (Figure 3). Figure 3: Boxplots of perceived task difficulty. (The red line represents the sample median. The distances between the tops and bottoms are the interquartile ranges. Whiskers show the min and max values; outliers are represented as a +). The dotted lines represent the division between the groups of tasks (fully described in table 1), in which the user is potentially assisted (left side) , tasks, in which the user is potentially hindered by resistance against movement generated by the device (middle) and tasks requiring participants to use a large range of motion (right side). Brackets indicate significant differences between the exoskeleton (with) and control condition (without). 0=very easy, 10=very difficult. In the group of tasks in which the user is potentially assisted by the exoskeleton, a significant difference was only found for forward bending, with a lower perceived task difficulty in the exoskeleton condition compared to the control condition (2.2 ± 2.55 vs. 5.3 ± 3.98; p=0.010). In the group of tasks in which the user is potentially hindered by the device, a significant increase of perceived task difficulty in the exoskeleton condition compared to the control condition was noted for walking (2.15 ± 1.55 vs. 0.20 ± 1.10; p=0.014), sitting (0.65 ± 2.08 vs. 0.20 ± 0.48; p=0.004), rotating (0.75 ± 1.63 vs. 0.10 ± 0.20; p=0.003), 3