Advanced Musculoskeletal Modeling and Kinematic Assessments for Comparing Occupational Exoskeletons Effectiveness and Muscle Dynamics in Laboratory and In-Field Environments
Creators: Shakourisalim, Maryam
Publisher: name: University of Alberta Library
Year: 2024

<p>This thesis investigates the effectiveness of occupational exoskeletons and assistive tools in reducing ergonomic risks associated with physically demanding tasks, specifically focusing on the comparison of in-lab and in-field assessments and the utilization of advanced musculoskeletal modeling techniques. This thesis outlines its comprehensive investigation into the ergonomic risks associated with occupational tasks, organized across several chapters. <br>
      The first study explores the biomechanical impact of using a back support exoskeleton and assistive tools (Lever and Jake) in the task of manhole cover removal.  The use of various tools and occupational exoskeletons was suggested to enhance physical capabilities of workers who regularly perform physically demanding tasks involving heavy lifting and awkward postures. Most of the studies aiming to explore the effectiveness of these tools and exoskeletons have been performed in confined and controlled laboratory spaces, which do not represent the real-world work environment. This study aimed to compare the outcome of biomechanical assessment of using a back support exoskeleton and assistive tools (Lever and Jake) in the procedure of manhole cover removal versus the results found by performing the same task in a laboratory. Ten able-bodied participants and ten able-bodied utility workers performed the same manhole removal task in-lab and in-field, respectively, with the aid of an exoskeleton and Lever and Jake tools. Muscle activity and Rapid Entire Body Assessment (REBA) scores were recorded using surface electromyography and inertial measurement units (IMUs), respectively, and compared between in-lab and in-field trials. The field experiments indicated significant differences (p &lt; 0.05) in normalized muscle activity across most muscles when compared to lab data. These results revealed how muscle activity is affected by the controlled lab setting compared to real-world field conditions. However, REBA scores indicate similar ergonomic implications regardless of the utilization of exoskeletons or tools. These findings underscore that real-world field assessments are crucial for evaluating ergonomic risks and effects of occupational exoskeletons and tools to account for environmental factors and workers’ skills in ergonomic evaluations of this nature. <br>
The second study focuses on assessing lower back muscle and joint reaction forces during a common workplace task of lifting a weight using wearable IMUs and camera-based motion capture system (MCS). Low back pain is frequently associated with occupational factors, including heavy lifting and poor ergonomics, and can lead to substantial healthcare costs and reduced productivity. Assessment tools for human motion and ergonomic risk at the workplace are still limited. Therefore, this study aimed to assess lower back muscle and joint reaction forces in laboratory conditions using wearable IMU during weight lifting, a frequently high-risk workplace task. Ten able-bodied participants were instructed to lift a 28 lbs. box while surface electromyography sensors, IMUs, and MCS recorded their muscle activity and body motion. The data recorded by IMUs, and MCS was used to measure lower back muscle and joint reaction forces via musculoskeletal modeling. Lower back muscle patterns matched well with electromyography recordings. The normalized mean differences between muscle forces obtained based on measurements of IMUs and cameras were less than 25%, and the statistical parametric mapping results indicated no significant difference between the forces obtained by both systems. However, abrupt changes in motion, such as lifting initiation, led to significant differences (p&lt;0.05) between the muscle forces obtained by these systems. Furthermore, the maximum L5-S1 joint reaction force calculated using IMU data was significantly lower (p&lt;0.05) than those obtained by cameras during weight lifting and lowering. The study showed that wearable IMUs had a potential for in-field assessments of lower back muscle forces, enabling the evaluation of in-field ergonomic risk assessment, optimizing posture and workstation, and ultimately reducing the risk of work-related musculoskeletal disorders.<br>
Integrating findings from both studies, this thesis highlights the potential of combining in-field and in-lab assessments using musculoskeletal modeling to better understand and mitigate ergonomic risks. This thesis introduces a novel approach by leveraging advanced musculoskeletal modeling techniques, such as the integration of IMU data and sophisticated statistical parametric mapping, to evaluate the potential of wearable sensors in ergonomic risks assessments. These advanced modeling techniques allow for a more precise simulation of human musculoskeletal dynamics under various real-world conditions, offering insights into muscle and joint forces that were previously challenging to obtain. By doing so, this innovative methodology not only enhances our understanding of ergonomic risk factors but also holds the potential to significantly reduce the prevalence of work-related musculoskeletal disorders. This marks a significant advancement in the biomechanics field by providing a comprehensive toolset for assessing and optimizing the use of occupational exoskeletons and assistive tools, contributing to safer work environments and better health outcomes for workers engaged in physically demanding tasks.</p>