Neural excitability and joint laxity in chronic ankle instability, coper, and control groups

Context: Neuromuscular and mechanical deficiencies are commonly studied in participants with chronic ankle instability (CAI). Few investigators have attempted to comprehensively consider sensorimotor and mechanical differences among people with CAI, copers who did not present with prolonged dysfunctions after an initial ankle sprain, and a healthy control group. Objective: To determine if differences exist in spinal reflex excitability and ankle laxity among participants with CAI, copers, and healthy controls. Design: Case-control study. Setting: Research laboratory. Patients or Other Participants: Thirty-seven participants with CAI, 30 participants categorized as copers, and 26 healthy control participants. Main Outcome Measure(s): We assessed spinal reflex excitability of the soleus using the Hoffmann reflex protocol. Participants' ankle laxity was measured with an instrumented ankle arthrometer. The maximum Hoffmann reflex : maximal muscle response ratio was calculated. Ankle laxity was measured as the total displacement in the anterior-posterior directions (mm) and total rotation in the inversion and eversion directions (8). Results: Spinal reflex excitability was diminished in participants with CAI compared with copers and control participants (P ? .01). No differences were observed among any of the groups for ankle laxity. Conclusion: Changes in the spinal reflex excitability of the soleus that likely affect ankle stability were seen only in the CAI group, yet no mechanical differences were noted across the groups. These findings support the importance of finding effective ways to increase spinal reflex excitability for the purpose of treating neural excitability dysfunction in patients with CAI.