Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Investigating the influence of cognitive demands and personal factors on work-body postures(Montana State University - Bozeman, College of Engineering, 2021) Nino, Luisa Valentina; Co-chairs, Graduate Committee: David Claudio and Scott Monfort; Frank Marchak and David Claudio were co-authors of the article, 'Evaluating physical and mental workload interactions in a sterile processing department' in the journal 'International journal of industrial ergonomics' which is contained within this dissertation.; Frank Marchak and David Claudio were co-authors of the article, 'Association between perceived workload and adverse body postures' in the journal 'Proceedings of the International Symposium on Human Factors and Ergonomics in Health Care' which is contained within this dissertation.Mental workload is a broad concept used by human factors and ergonomics professionals. It has become a topic of increasing importance since the introduction of technology in modern working environments. Mental workload assessment is an important component in the design of occupational tasks since inappropriate levels can cause errors, incidents, and be responsible for occupational diseases and musculoskeletal disorders. Until now, research studies have explored the effects of physical activity on mental workload. No study has analyzed the effects of mental workload on body postures even though studies have stated that in response to new information from the workplace environment, the human body orients in the direction of a stimulus, and this orientation reaction could affect the ongoing activity. This dissertation looked to 1) determine if psychosocial work factors affect perceived mental workload, 2) determine if changes in perceived mental workload generated changes in the body postures undertaken to perform an activity, and 3) explore if individual factors such as age, sex, personality traits, and anxiety mediate or exacerbate the influence of psychosocial work factors. Thirty-two participants performed two physical activities under four levels of mental workload. The results indicate, for the first time, that an increase in the perception of mental workload is associated with worse body postures that consequently could lead to work-related musculoskeletal disorders (WMSDs). Regarding the potential influence of individual factors, differences were not observed between mental workload conditions. However, individual characteristics such as anxiety, personality traits, and sex exhibited higher contributions to changes in perceived mental workload and body postures. This study is novel and contributes to overcoming an important shortcoming in the field of mental workload by considering the influence of psychosocial factors, keeping the physical load constant, on the perception of mental workload and its influence on body postures. This interaction between perceived mental workload and its effects on physical risk should be considered in occupational settings since often, employees are exposed to concurrent physical and mental demands that increase the likelihood of developing WMSDs.Item Methodological considerations and clinical utility of analyzing transient behavior in quiet stance postural control(Montana State University - Bozeman, College of Engineering, 2020) Reed, Cody Aaron; Chairperson, Graduate Committee: Scott Monfort; Ajit M.W. Chaudhari, Lise C. Worthen-Chaudhari, Kimberly E. Bigelow and Scott M. Monfort were co-authors of the article, 'A new perspective on transient characteristics of quiet stance postural control' in the journal 'PLOS ONE' which is contained within this thesis.; Scott M. Monfort were co-authors of the article, 'Influence of a cognitive perturbation on transient characteristics of quiet stance postural control' submitted to the journal 'Gait & posture' which is contained within this thesis.Postural control has been widely studied to provide insight into various health concerns. Traditionally, postural control is assessed using whole-trial analysis techniques that measure center of pressure parameters as a singular estimate for an entire trial. These whole-trial estimates may be more reliable for longer duration trials. However, longer trials and whole-trial analyses mask transient (i.e., a destabilized period followed by a transition to a more stable, quasi-steady state level) responses within center of pressure data. By only using whole-trial estimates, we may be missing out on unique information that is contained within this understudied aspect of postural control. Therefore, four experiments were conducted to better understand the clinical utility of evaluating transient postural control behavior. The first experiment tested whether transient, epoch-based characteristics of center of pressure parameters provided unique information compared to traditional whole-trial estimate approaches. The second experiment evaluated participants in eyes open and closed conditions to test whether transient behavior was a sensory reweighting response to eye closure. The third experiment tested whether transient characteristics of postural control could distinguish between younger and older adults. Based on the results of the first three experiments, a fourth experiment was conducted to investigate the influence of cognitive perturbations on transient characteristics of postural control. Negligible correlations were found between transient characteristic and whole-trial estimates, indicating that unique information is contained in transient measures of postural control. Although transient behavior was exaggerated during eyes closed stance, transient behavior still existed during eyes open stance. In addition, select transient characteristics distinguished between young and older adult groups, supporting the clinical relevance of transient measures. Lastly, cognitive perturbations influenced transient postural behavior, supporting the use of transient measures for analyzing dual-task scenarios. Overall, our results support the use of epoch-based estimates to characterize transient postural behavior as a complementary assessment to traditional whole-trial analyses. Our results also indicate the need to carefully consider how postural control trials are analyzed and initiated. Moving forward, further evaluation of transient characteristics of postural control is warranted to determine their relationship to health outcomes such as falls.