Saskia Baltrusch

66 Chapter 3 developments need to focus on higher adaptability of the device to different tasks, providing unrestricted range of motion and wearing comfort by the exoskeleton. There are several limitations to this study. First, the time to get habituated to the device before performing the different tasks was relatively short. Since there was no fixed try-out protocol at the start of the experiment some participants might have been habituated more than others when starting the test battery. In future studies, it would be beneficial to have an identical habituation protocol for each participant. Another limitation is, that the test protocol was performed in a laboratory. The selected tasks represented a variable work setting. However, the controlled laboratory setting limited the risk of severe adverse effects and hence we cannot evaluate potential safety risks. Therefore, a future field study is needed to assess the effect of an exoskeleton on the functional performance and on safety in a real work setting. Also, we only assessed functional performance, but did not observe how the change in performance could be explained in terms of change in movement strategy. Future research should address that topic in more detail. Furthermore, this study was limited by a short duration of the tasks tested. The effect of the exoskeleton in long-term use and the effect of a longer time period on perceived task difficulty and discomfort require further study. 5 Conclusion In conclusion, the present study shows that the passive trunk exoskeleton affected functional performance in healthy individuals both, positively and negatively. It decreased the local discomfort in the back in static holding tasks and the local discomfort at the dorsal side of the upper legs in static forward bending and therefore assisted the user when performing these tasks. The exoskeleton showed adverse effects on tasks that require large ROM of trunk or hip flexion including walking. It was shown that perceived discomfort by the device is not directly related to performance in the short-term use of the exoskeleton. Based on these results it can be concluded that this type of exoskeletons has its most important application in working environments with stereotypical tasks, such as assembly work in a forward bent position, but has important limitations in environments that require more versatility. Directions for improvement of the design to allow more versatility and its acceptance and applicability in more work settings include the possibility to disengage the device to allow unrestricted hip flexion and to improve general comfort of the device.