The Effect of Functional Fatigue on Dynamic and Static Balance Indexes in Athletes with Ankle Instability

Although it is obvious that physical fatigue leads to impaired balance in healthy athletes, it is still a question that how does functional fatigue can affect balance in athletes with ankle instability. Therefore, the aim of this study is to determine the effects of functional fatigue on dynamic and static balance index in athletes with ankle instability. Fifteen volleyball players with ankle instability participated voluntarily in this study (age,19.4 ± 1.9y; height, 1.825 ± 5.2m; weight, 67.7 ± 5.9kg; BMI, 20.3 ± 1.6kg/m2).In order to apply fatigue, functional fatigue protocol special for volleyball was used, and for quantity of balances the Biodex Balance System was applied. During the study, four times (two times without fatigue, and two times after fatigue) the balance test was performed by Balance system (single leg stability testing in difficult level of 4 for dynamic balance and in difficult level of 12 for static balance). For statistical analysis of data a significant level p ≤ 0.05 was used. Data analysis with paired t-test showed that after applying functional fatigue, dynamic (1.600 to 1.838) and static (1.238 to 1.462) balance index had significant increase. Decrease of dynamic balance, when applying fatigue can be due to a significant increase in anterior-posterior balance index (1.085 to 1.246); but in static conditions the decrease in balance can be due to a significant increase of both the anterior-posterior (0.869 to 1.046) and medial-lateral (0.800 to 0.900) balance index. Based on the research results, decrease of dynamic and static balance of players with ankle instability during fatigue may make them susceptible to ankle sprain injury.