The impact of fatigue on static balance in people with chronic ankle instability.

Purpose: The aim of the study was to assess static postural stability under fatigue in subjects with chronic ankle instability - "copers" in comparison with healthy controls.

Methods: We conducted a prospective study on a group of 60 young, physically active subjects, divided into 3 groups: I - 14 subjects with unilateral ankle instability, II - 15 subjects with bilateral ankle instability, III - 31 healthy subjects, without ankle instability. The fatigue trial was based on modified Short-Term Fatigue Protocol. Static stabilography was performed with the use of HUR platform.

Results: showed an increase in the value of COP trace length after fatigue test in study population I. The level of COP trace length Z before fatigue was significantly lower than after fatigue. Subjects from study population I had higher levels of COP trace length Z in comparison with the control group. The main effect for the group also proved to be significant. Study population I had higher levels of COP trace length Z in comparison with the control group. For the measurement after fatigue, there was significant difference only between the study population I and the control group.

Conclusions: The incidence of structural ankle instability was not correlated with functional instability. Subjects with ankle instability, or "copers", had good functional levels, enabling them to perform sports activities. "Copers" had weakened proprioception in static stabilography tests. Short and intense fatigue protocol weakened the ability to maintain balance in static stabilography test with eyes closed.