Methodological considerations and clinical utility of analyzing transient behavior in quiet stance postural control
Reed, Cody Aaron
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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.