Altered spinal-level sensorimotor control related to pain and perceived instability in people with chronic ankle...

To compare soleus spinal reflex excitability, presynaptic inhibition and recurrent inhibition between chronic ankle instability (CAI), acute Lateral Ankle Sprain coper (LAS-coper) and healthy populations. The relationship between spinal reflex excitability and pain and perceived instability in people with CAI was also examined.

Cross-sectional laboratory experiment.

Twelve individuals with CAI, twelve 'copers' and twelve healthy age, limb and gender-matched controls participated. Soleus H-reflex recruitment curves, pre-synaptic excitability and recurrent inhibition of the spinal-reflex pathway were examined during static double- and single-leg stance. Reporting of pain and perceived instability were used to perform a regression analysis on measures of soleus spinal excitability in people with CAI, LAS-coper and healthy controls.

Soleus spinal reflex excitability was greater during single-leg stance in CAI compared to healthy and coper individuals (p=<0.001). Pre-synaptic inhibition was three-times less in CAI participants compared to both healthy controls and copers (p=<0.001). There were no differences between healthy and coper participants in spinal-level measures of sensorimotor control. Reports of pain explained 15-16% of the variance in soleus spinal reflex excitability and presynaptic inhibition during single and double-leg stance, while perceived instability explained 20% of the variance in spinal reflex during single leg stance only.

CAI participants presented with an inability to suppress soleus spinal reflexes during tasks with increased postural threat; likely due to disinhibition of pre-synaptic mechanisms. Pain and perceived instability may contribute to changes in spinal-level sensorimotor control in CAI.