Saskia Baltrusch

137 Chapter 5 Functional Testing Three men with no low-back pain history participated in the functional testing of the prototype. Participants performed a series of functional tasks, including (1) tasks to assess the supportive function of the device, (2) tasks to assess the extent of restricted hip flexion, and (3) tasks to assess the ROM. A detailed description of the tasks can be found in a previous study of Baltrusch et al. (2018) [26], who developed a test battery to assess the effect of a passive trunk exoskeleton on functional performance. For convenience the tasks are also listed in Figure 12B. The functional tasks were performed once with an exoskeleton and without any exoskeleton. The sequence of the tasks and the starting conditions were randomized to prevent order and habituation effects. Functional performance was assessed by using questionnaires after each task, asking for perceived task difficulty and discomfort of the device. At the end of the session participants had to fill in a user’s impression questionnaire regarding their experience with the exoskeleton during the test session. The subjective outcomes measures were all assessed by using a visual-analog scale (VAS). This allows to more accurately distinguish between participants opinion compared to numeric scales [40]. User’s impression: The users impression questionnaire was divided into the assessment of range of motion, efficacy, and overall impression of the prototype. For range of motion participants got asked “Are you restricted in your freedom of movement?” with a VAS scale ranging from “not restricted” to “heavily restricted.” For assessing the efficacy of the device participants had to answer questions based on the reduction of back loading (“Does the device reduce the loading on your back?”; 0 = high reduction, 10 = no reduction), the support of tasks (“Does the device support you in performing the tasks you did?”; 0 = high support, 10 = no support) and the interference with tasks (“Does the device interfere with the tasks you did?”; 0 = no interference, 10 = high interference). To assess the overall impression participants were instructed to grade the device on a VAS scale with 0 = very bad and 10 = perfect. Perceived task difficulty: To indicate the perceived task difficulty after each task participants were asked to put a cross on a VAS scale ranging from “very easy” to “very difficult,” with the question: “How difficult was the task you just 5