Ergonomics Assessment of Minimalist Sit-Stand Exoskeleton for Rapid Postural Adjustment Tasks

Abstract

Introduction: In industrial workplaces, static postures during standing and sitting pose risks for musculoskeletal disorders (MSDs), impacting worker health and leading to significant economic costs. Traditional sit-stand exoskeletons often fall short in dynamic settings. This study presents the Minimalist Sit-Stand Exoskeleton (MSSE) prototype, designed to enable rapid postural changes and reduce physical strain by facilitating smooth transitions between sitting and standing. Materials and Methods: This study involved 10 healthy males for electromyography (EMG) and contact pressure assessments, and 60 participants (30 males and 30 females) for usability testing of the MSSE prototype. They performed a simulated electrical plug assembly task, requiring rapid posture adjustments. Muscle activity was measured using DELSYS Trigno EMG sensors on key lower-limb muscles (bicep femoris, rectus femoris, vastus medialis, and vastus lateralis) with and without the MSSE prototype. Contact pressure between the MSSE prototype and the user’s body parts was recorded using the CONFORMat system. Usability was evaluated using a modified System Usability Scale (SUS) after wearing the MSSE prototype for 3 hours. Results: The MSSE prototype was able to reduce muscle contraction in lower-limb muscles compared to standing without it, improving muscle endurance. When wearing the MSSE prototype, contact pressure was negligible while standing but increased to 23.9 kPa under the thighs and 29.9 kPa under the calves when sitting. The MSSE prototype received a SUS score of 58.13, indicating acceptable performance but suggesting the need for usability improvements. Conclusion: The MSSE prototype shows promise but requires further usability enhancements to improve overall effectiveness.