ABSTRACT
Objective To explore the static postural balance in individuals with or without functional ankle instability (FAI)by identifying and quantifying the spatial characteristics of center of pressure (COP),as well as rambling and trembling trajectory properties.Methods Twelve FAI patients was selected into the FAI group,while another 14 healthy students were chosen into the control group.The single-leg standing test with and without vision was conducted on the unstable side of the FAI group and the non-dominant side of the control group 3 trials with each trial lasting 30 s.The displacement of COP and the time and frequency domain of rambling and trembling were analyzed and compared between the two groups.Results There was no significant difference in the displacement of COP with opened eyes(P＞0.05).The area and the anterior-posterior length of COP of the FAI group were larger than those of the control group with eyes closed (P＜0.05).For the rambling and trembling trajectory,no significant differences were found in all the time domains between the two groups with eyes open or closed(P＞0.05),except the mean sway amplitude(MSA)(P＜0.05).Moreover,the mean square root and standard deviation of MSA of the FAI group were significantly bigger than the control group(P＜ 0.05).Significant differences were found in the MSA frequency between open and closed eyes(P＞0.05),but not between the FAI and control groups(P＜0.05).Conclusions The FAI patients are weaker than healthy people not only in the peripheral control,but also in the central control of the static postural balance.Therefore,injuries in the central neural system must also be considered when analyzing the reason for FAI.The imbalance of the FAI patients can be avoided by opening eyes.