Saskia Baltrusch

169 Chapter 6 the perceived support and the perceived reduction of back loading, assessed with the User’s Impression Questionnaire, was only graded moderate to good with high variability between subjects. Therefore, support in these tasks should be improved to increase user acceptance. In the group of tasks for assessing potential hindrance by and range of motion in the device, objective performance slightly decreased in walking, stair climbing, and wide stance. The reduced performance in walking and stair climbing can mainly be explained by the weight of the exoskeleton (6kg), which is as heavy as current active exoskeletons like the MuscleSuit [19]. In our study, participants complained about pressure on the hips when moving with the device, increasing over time. Besides the weight, participants also complained about the dimensions of the exoskeleton, hindering arm swing during walking. In addition to a decrease in performance, walking coincided with the highest discomfort levels, suggesting that a decrease in weight and dimension could help to prevent discomfort in this task. In general, discomfort levels were low but showed high variability, indicating that perceived comfort of the device is highly subjective. The remaining tasks of the group for assessing potential hindrance and range of motion were not affected by exoskeleton use. Regarding subjective performance, those tasks were not perceived as more difficult and the local discomfort in the lower back did not change. These findings imply little hindrance during tasks that do not involve high loads on the back. This is important as those tasks exist in most of the working environments, hence versatility to use this exoskeleton for a variety of working tasks is deemed important. The good to very good user impression score on “Interference with tasks” confirms that the current device meets this requirement. Limited versatility was found to be a drawback of a currently market-available exoskeleton [14]. In the SPEXOR device, versatility was improved mainly by implementing a clutch that can be switched on and off manually, depending on whether support is needed for a certain task or not. The findings of performance and user satisfaction show that this helped in providing improved range of motion and less task interference. The results of the User Impression questionnaire suggest that especially issues on the perceived efficacy need to be addressed to increase user satisfaction and the intention to use the device at work. The technology acceptance model 6