Segmental Spinal Reflex Adaptations Associated With Chronic Ankle Instability

Sefton JM, Hicks-Little CA, Hubbard TJ, Clemens MG, Yengo CM, Koceja DM, Cordova ML. Segmental spinal reflex adaptations associated with chronic ankle instability. Objective: To further understanding of the role that segmental spinal reflexes play in chronic ankle instability (CAI). Design: A 2 × 2 repeated-measures case-control factorial design. The independent variables were ankle group with 2 levels (healthy, CAI) and stance with 2 levels (single, double legged). Setting: University research laboratory. Participants: Twenty-two participants with CAI and 21 matched healthy controls volunteered. Interventions: Not applicable. Main Outcome Measures: The dependent variables were 2 measures of motoneuron pool excitability: paired reflex depression (PRD) and recurrent inhibition. Results: A 2 × 2 repeated-measures multivariate analysis of variance revealed a significant interaction between group and stance on the linear combination of PRD and recurrent inhibition variables (Wilks λ=.808, F_2,40=4.77, P=.014). Follow-up univariate F tests revealed an interaction between group and stance on the PRD (F_1,41=9.74, P=.003). Follow-up dependent t tests revealed a significant difference between single- and double-legged PRD in the healthy participants (t₂₀=-3.76, P=.001) with no difference in CAI participants (t₂₁=-0.44, P=.67). Finally, there was a significant difference in recurrent inhibition between healthy (mean, 83.66) and CAI (mean, 90.27) (P=.004). Conclusions: This study revealed that, compared with healthy participants, CAI participants were less able to modulate PRD when going from a double- to a single-legged stance. Additionally, CAI participants showed higher overall levels of recurrent inhibition when compared with healthy matched controls.