Over the last 40 years, a new paradigm has been posited where the variability observed in physiological systems is a consequence of the interactions occurring between the various components that affect the system. While quantifying the magnitude of variability can be useful, analyses that measure how the structure of the variability (dynamics) changes over time have been posited to reflect the health of the system. Many researchers interpret the results of these analyses to be indicative of the system’s adaptive capacity. While there is ample indirect evidence to support this notion, a lack of direct findings has left the literature lacking a definitive foundation to move forward with this interpretation. While many physiological systems are too invasive to safely perturb, the movementbased systems are routinely perturbed in real-world environments without dire consequences. Of particular interest is the locomotor system, which is constantly challenged in real-world environments via slips and trips. Furthermore, the locomotor system can be safely and validly perturbed in the laboratory. A range of locomotor dynamics-based measures have been used to describe differences between various clinical populations, but none have been directly associated with a person’s ability to remain upright when perturbed. The objectives of this study are to (1) examine the relationship between locomotor dynamics/stability to overall fall-risk prior, (2) examine how locomotor dynamics relate to the ability to recover from a trip via global stability, and (3) determine the extent to which an acute trip-training session alters locomotor dynamics and global stability. Forty healthy, older adults (75.2 ± 4.9 yrs) were recruited by convenience from the local community. The participants completed a variety of clinical assessments in order to determine overall fall-risk. Afterwards, they participated in three walking trials consisting of: 1) a 15-minute unperturbed walking session, 2) a 10-minute unperturbed walking session (control) or a 10-minute trip-training session (intervention), and 3) a 15-minute unperturbed walking session. Various measurements of locomotor dynamics and adaptability were calculated from full-body 3-D kinematics collected at 100Hz. Multiple regression and repeated measure analysis of variance models were calculated to determine to what extent locomotor dynamics and adaptability relate to one another and how an acute trip-training session affects their relationship. The results from our first experiment suggested that locomotor dynamics and stability during steady state do not significantly relate to overall fall-risk. However, the second experiment showed that locomotor dynamics are predictive of an individual’s ability to recover from a trip. Our last experiment showed the feasibility of using an acute trip-training session to alter locomotor dynamics and stability. These data represent the first direct evidence of physiological variability being indicative of adaptive capacity in the locomotor system. Further investigation will be necessary to determine the robustness of the analyses to indicate adaptive capacity across perturbations and populations.
|Advisor:||Rhea, Christopher K.|
|Commitee:||Lockhart, Thurmon E., Raisbeck, Louisa D., Ross, Scott E.|
|School:||The University of North Carolina at Greensboro|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 79/11(E), Dissertation Abstracts International|
|Keywords:||Balance, Complexity, Dynamics, Fall risk, Locomotor, Stability|
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