COP excursion and muscle activation during gait initiation in chronic ankle instability(CAI)

Abstract

Abstract The aim of the current study was to evaluate center of pressure (COP) excursion and muscle activation during gait initiation (GI) in chronic ankle instability (CAI) Individuals. 34 young men were selected in two groups as, CAI and healthy groups. The subjects were started walking with barefoot in minimum delay on a force plate as they heard the auditory cue. Reaction time (RT), Anticipatory Postural Adjustments (APA) time, peak COP excursion during RT and APA time were calculated. Although response time of Soleus (SO) and Tibialis Anterior (TA) muscles were recorded by electromyography signals. A longer RT and shorter APA time of GI was noted in the CAI group compared with the healthy group (p < 0.05). The results indicated no significance difference in peak COP excursion between the groups (p > 0.05). Although, response time of SO was significantly longer than TA in healthy group (p < 0.05) (which means SO muscle inhibition occurred in the early of GI). However, it did not indicate significant different between SO and TA muscles in CAI group (p > 0.05) (which means SO muscle inhibition did not occur in the early of GI). It seems that in the CAI group, the increasing of the RT has been compensated by the supra-spinal pathways due to the reducing of the APA time; it seems muscle inhibition did not occur in CAI group. These alterations strongly suggest that centrally modification to motor control may be an important contributor to the neurophysiologic mechanism of CAI.