The purposes of the present work were: 1) to develop a computerized model that could predict the personal lift-assist device (PLAD) spring excursion and control spring stiffness for various individuals based on their anthropometry and working posture and 2) to test the PLAD’s (Version 6) effectiveness and user acceptability during static forward bending in an automotive assembly plant. Study 1 required 30 subjects to carry out a protocol that simulated unloaded stoop, squat, and freestyle lifting. Trunk inclination and knee angles were determined via 3 FastrakTM sensors, whereas a displacement transducer attached in-line with the PLAD determined excursion when the trunk or knees flexed. A model was created to determine spring excursion, and it was successfully validated with 10 additional subjects. A computerized model applying the excursion model and mathematical equations was also developed to calculate the required spring stiffness for offsetting a proportion of the L4/L5 bending moment for each individual in various postures. Study 2 investigated the effectiveness and user acceptability of the PLAD at an automotive manufacturing facility, using operators who performed an assembly process requiring forward bending and static holds. Surface EMG data were collected at six sites on the low back and abdomen, and a tri-axial accelerometer was mounted on each subject’s sternum to measure trunk inclination. A 20% reduction in the L4/L5 bending moment was provided to each wearer using the aforementioned computerized model. The PLAD was able to significantly reduce low back muscular activity, predicted-compression, and ratings of perceived exertion, without significantly changing abdominal activity or trunk inclination. Workers had positive opinions about the device, and 80% said they would wear the device everyday on-line. Additionally, the computerized model developed in Study 1 was effective, as worker low back muscular activity was reduced by approximately 20% when wearing the PLAD. With slight alterations, the PLAD appears to be beneficial in reducing low back forces and discomfort in many tasks that place excessive biomechanical loading on the low back. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2008-08-18 15:55:16.757

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The purpose of this research is twofold: 1) to apply a user-centred approach to examine the usability and acceptability of an on-body ergonomic aid called the Personal Lift Assistive Device (PLAD) in a variety of industrial work environments and 2) to utilize subjective user acceptability data on discomfort, pain and overall PLAD assessment by participants to identify design features that need improvement in the next PLAD iteration. Case studies took place in four different industrial work environments: two distribution centre environments, one retail store environment and one automotive assembly plant environment. These environments were selected to represent different industrial work environments. In total, 20 industrial workers were selected to wear the PLAD and provide their feedback. Results were obtained using subjective questionnaires through verbal and written comments as well as through direct observation of the participants. Three major design changes occurred to the original PLAD iteration tested at the first industrial location. These included: 1) using different stiffness levels of springs for different sizes of individuals in an attempt to decrease discomfort and optimize the effectiveness of the PLAD, 2) an increase in pelvic spacer size and surface area contacting the user’s body to reduce discomfort and 3) modification to the shoulder harness including; shape, dimensions and amount of cushioning to reduce discomfort. Currently, three major design changes were identified and still need to be addressed. These include: 1) reduction of thermal discomfort caused by wearing the PLAD, 2) validation of selecting the appropriate spring stiffness for small, medium and large users of the PLAD (male and female) under various working postures and 3) simplification of the donning and doffing process. Additionally, a simple PLAD spring stiffness sizing chart was created to aid potential manufacturers of the PLAD to select the appropriate spring stiffness for various users of the PLAD. This sizing chart was designed to maintain an average lumbar moment reduction of 15%, while taking discomfort of the shoulders caused by the spring stiffness and overall cost into consideration. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2011-09-28 09:03:01.463

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