Date of Award

6-26-2026

Date Published

July 2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Exercise Science

Advisor(s)

Jason DeFreitas

Keywords

Aging;Balance Recovery;Fall Assessment;Fall Risk

Abstract

The primary objective of this dissertation was to test the validity and sensitivity of a novel fall risk assessment and investigate the sensorimotor factors that prevent a fall. Study 1 was designed to validate a novel reaction time test and see if it was sensitive enough to correctly assign an older adult’s fall status. The evidence showed a significant difference between young and non-faller older adults (p < 0.001) and young and faller older adults (p = 0.040), supporting the existing literature. Although there was no significant difference between the older and fallers (p = 0.037), the reaction time test was able to accurately assign adults with their fall status, accurately placing 25% of the 36% of actual fallers into the fall status category. Study 2 examined if traditionally used measures of functional health could predict an older adult’s postural performance following random perturbations at increasingly difficult intensities. Stepwise multiple regression results indicated that gait speed (p < 0.001) and balance performance (p < 0.001) were significant predictors at the lowest perturbation intensity with no distractions (single-task), and plantarflexor strength (p < 0.001) was a significant predictor at all intensities with the addition of a distraction (dual-task) for stride length performance. There were no significant predictors of bilateral symmetry performance (p > 0.05). Study 3 examined the physiological mechanisms behind postural responses following a sudden perturbation. Stepwise multiple regression results indicated that H-reflex amplitude while standing was most common significant predictor at all perturbation intensities and tasks (p < 0.001), with the addition of premotor reflex latency as a significant predictor during the moderate and high perturbation intensities (p < 0.001) for stride length performance. VL EMG peak-peak amplitude was the only significant predictors of bilateral symmetry performance at all intensities with the addition of a distraction (p < 0.001) These results helped fill in the gap that was left by study 2, indicating that as perturbation intensities become more difficult and attentional demand is divided, the spinal stretch reflex, measured by H-reflex amplitude while standing, and the Vastus Lateralis EMG peak-peak amplitude, is a significant predictor to an adult’s postural performance and response. The findings across these three studies collectively advance our understanding of the physiological and functional factors of reactive postural control in older adults.

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