Proof of Prototype: A Biomechanical Evaluation of aPassive Exoskeleton for Lower BackInjury Prevention Among Loggers

Sammanfattning

Background Manual logging is a physically demanding task, exposing workers to awkward postures and high biomechanical loads, particularly in the lower back. Despite technological advances, manual tree felling is still widely used and solutions to reduce long-term musculoskeletal risk remain limited. Purpose and Aim The aim of this study was to conduct a proof of prototype biomechanical evaluation of the passive back-supporting exoskeleton developed by Husqvarna for use in logging work. The study focused on assessing whether the device reduces muscle activity in the erector spinae and maintains range of motion during simulated forestry tasks. As the first study to evaluate the prototype, this thesis also explored user experiences to gain preliminary insights into its practical usability and perceived comfort. Methods Eight male participants with logging experience completed six tasks, including Range of Motion (ROM) and functional logging tasks. All tests were performed in a motion capture lab with and without the prototype exoskeleton. Electromyography (EMG) and ROM data were collected, and subjective feedback was obtained using a post-test survey. The evaluation was structured using an adapted Double Diamond framework informed by emphatic principles from the Bootleg design approach, focusing on systematic testing and user-centered analysis within the ‘test and refine’ phase of development. While no redesign iterations were implemented in this study, the framework supported a structured approach to identifying design limitations and suggesting future improvements. Results No statistically significant reduction in muscle activity was found when comparing tasks performed with and without the exoskeleton, although moderate effect sizes suggest potential benefits under certain conditions. Significant ROM restrictions were found in hip and trunk rotation, which could affect task execution. Survey feedback highlighted issues with fit, comfort, and adjustability, although most participants agreed the exoskeleton helped maintain posture. Conclusion The exoskeleton did not significantly reduce muscle activity of the erector spinae, however, a significant reduction in range of motion in rotation was observed in the hip and trunk. This confirms concerns about limited range of motion when using the exoskeleton. User feedback indicated discomfort and mobility constraints while improving posture control. Results highlight design improvements in ergonomics and load distribution. Future research should also explore long-term adaptation, compensatory strategies and real-world performance of the exoskeleton.