Date of Award

Spring 2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Rehabilitation Sciences

Program/Concentration

Kinesiology and Rehabilitation

Committee Director

Ryan S. McCann

Committee Member

Eric J. Schussler

Committee Member

Emily H. Gabriel

Committee Member

Ashley M. B. Suttmiller

Abstract

Chronic ankle instability (CAI) is a neurophysiologic deficit resulting in diverse sensorimotor impairments. Following acute ankle sprains, pain, mechanical instability, and joint deafferentation reduce sensory input to the central nervous system (CNS). In response, the CNS sends altered motor signals to lower extremity muscles. These CNS changes contribute to various neuromuscular impairments in CAI patients, the most common of which is reduced balance performance. Specifically, CAI patients struggle to modulate spinal reflex excitability of the soleus muscle when progressing from simpler to more complex balance tasks. This overreliance on spinal reflexes results in inconsistent activation of the ankle stabilizing muscle. To maintain balance effectively, spinal reflex excitability should be suppressed, and motor control should shift to the supraspinal center. However, CAI patients exhibited reduced supraspinal control of the soleus, as evidenced by increased cortical inhibition of the soleus muscle measured through transcranial magnetic stimulation (TMS). Thus, improving balance and restoring CNS function are among the most crucial goals for rehabilitation in individuals with CAI.

The aim of the first study was to examine the effects of a single balance training session on spinal reflexive excitability modulation, corticospinal excitability, and balance performance in individuals with CAI. This study revealed that single-session balance training began to increase spinal reflexive excitability modulation and corticospinal excitability in people with CAI. This supports the hypothesis that balance training might be able to transfer balance control to the supraspinal level to maintain single-limb standing in those with CAI.

Although current balance training has successfully improved balance performance in CAI populations, there is still heterogeneity in training parameters. The purpose of the second study, which was a systematic review and meta-analysis, was to determine the optimal dose of balance training for individuals with CAI. This study suggested that 6 weeks, 3 sessions a week, 18 total training sessions, and equal to or less than 20 minutes as the current optimal dose of balance training for people with CAI. Providing the optimal dose can be expected to reduce the heterogeneity of balance training parameters, reducing confusion for clinicians seeking the best intervention for their patients.

Using the results of Study 2, Study 3 aimed to determine the effects of 6-week balance training on spinal reflexive excitability modulation, corticospinal excitability, and balance performance in individuals with CAI. The results of this study exhibited increased spinal reflexive excitability modulation, corticospinal excitability, and balance performance following 6-week of balance training. This suggested that balance training was effective in addressing the neurosignature, which was accompanied by improved balance performance in those with CAI. Given that these neurophysiological deficits can contribute to recurrent ankle sprains, the improved neurosignature after balance training can provide an insight into why balance training has been considered one of the most important rehabilitation protocols preventing repetitive ankle sprains with improved balance performance in those with CAI.

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DOI

10.25777/z8xr-c546

ISBN

9798382774527

ORCID

0000-0001-6942-4299

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