Abstract
The purpose of this dissertation was to examine neural excitability of the fibularis longus (FL) in patients with and without acute ankle sprains (AAS) during single-leg balance 2) corticospinal excitability of FL in patients with and without AAS during single-leg balance and relationships between corticospinal excitability of FL during single-leg balance and postural control measures in single-leg balance in individuals with and without AAS. For study 1, fourteen patients with AAS (19.8±2.0yrs) and 14 uninjured controls (20.7±2.3yrs) volunteered. We measured the Hmax/Mmax ratio, H-reflex, and H-latency for spinal excitability during a single-leg balance position. There was no significant difference in spinal excitability between the two groups. These results suggest that spinal excitability of FL is not altered after AAS during single-leg balance. For study 2, the same subjects from study 1 were included in the study. We used an outcome measure of the normalized motor evoked potential (MEP) to quantify the corticospinal excitability. Transcranial Magnetic Stimulation (TMS) was provided once participants maintained a single-leg balance position. We also quantified single-leg balance performance with Center-of-Pressure (COP) excursion. We found the MEP in patients with AAS was significantly higher than that of uninjured participants. As expected, our AAS group presented impaired postural control. Further, impaired postural control was correlated with increased corticospinal excitability. Our findings are unique in that AAS may alter the corticospinal excitability during single-leg balance. The facilitated excitability in the FL suggests the compensatory supraspinal mechanism to maintain a single-leg stance for 10 seconds following AAS.