title: Quadratic Association Between Corticomotor and Spinal-Reflexive Excitability and Self-Reported Disability in Participants With Chronic Ankle Instability.
abstract: Spinal-reflexive and corticomotor excitability may have a critical role in altering muscle function needed to stabilize the ankle in people with chronic ankle instability (CAI).
  
  
  
  To determine the association between self-reported disability and both spinal-reflexive and corticomotor excitability in people with CAI.
  
  
  
  Descriptive laboratory study.
  
  
  
  Research laboratory.
  
  
  
  30 participants with CAI.
  
  
  
  Soleus spinal-reflexive excitability was measured with normalized Hoffmann reflexes (H:M ratio), and corticomotor excitability was measured with transcranial magnetic stimulation and quantified by normalized motor-evoked-potential (MEP) amplitudes at 120% of active motor threshold (120%MEP). Self-reported disability was quantified with the activities-of-daily-living and sport subscales of the Foot and Ankle Ability Measure (FAAM-ADL and FAAM-S). Separate linear Pearson product-moment correlations and nonlinear quadratic correlations were used to determine associations between the neural-excitability and disability variables.
  
  
  
  Thirty participants were included in the spinal-reflexive-excitability analysis, while only 19 were included in the corticomotor analysis. There was a significant, weak linear association between H:M ratio and FAAM-ADL (R = .39, P = .03) and a nonsignificant, weak linear association between H:M ratio and FAAM-S (R = .36, P = .06). There were significant, moderate quadratic associations between H:M ratio and both FAAM-ADL (R = .48, P = .03) and FAAM-S (R = .50, P = .02). There was a significant, moderate linear association between 120%MEP and FAAM-ADL (R = -.48, P = .04) and a nonsignificant, moderate negative linear association between FAAM-S (R = -.42, P = .07). There was a significant, moderate quadratic association between 120%MEP and FAAM-ADL (R = .57, P = .046) and a significant, strong quadratic correlation between 120%MEP and FAAM-S (R = .71, P = .004).
  
  
  
  There are significant quadratic associations between self-reported disability and both spinal-reflexive and corticomotor excitability of the soleus. CAI participants with low or high neural excitability present with lower function.
authors.affiliation: Dept of Exercise and Sports Science, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Matthew
authors.initials: M
authors.lastname: Harkey
authors.forename: Michelle M
authors.initials: MM
authors.lastname: McLeod
authors.forename: Masafumi
authors.initials: M
authors.lastname: Terada
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Gribble
authors.forename: Brian G
authors.initials: BG
authors.lastname: Pietrosimone
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000843:Ankle Joint / Q000503:physiopathology*; D002908:Chronic Disease; D000071080:Cortical Excitability; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D057566:Self Report; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult