Objective: The aims of this study were to identify the most appropriate indicator to assess the balance in the sudden perturbation test conditions.

Methods: In this study, 13 freestyle national wrestlers at the age of 20.5±2.4 and 13 normal subjects with average age of 23.5±1.4 were used recruited. Balancing test was carried out under two conditions: standing with the guard (guard) and stand feet shoulder width apart (standing). To measure the balance parameters, the RS-scan system was used, and for external perturbation movable plant with weights equal to 12% of the mass was used. The independent t-test for statistical analysis in each direction between the two groups was used.

Results: Center of pressure (CoP) travel distance in the anterior, posterior and external directions, wrestlers were more than those in normal individuals in both positions; for guard position (p = 0.01, p = 0.01, p = 0.5) and (p = 0.2, p = 0.5, p = 0.01) in stand position. The COP average speeds in the anterior, posterior and external directions in both conditions were more in wrestlers than that normal group, (p = 0.01, p = 0.08, p = 0.01) in the guard position and (p = 0.27, p = 0.1, p = 0.01) in the stand position. The wrestlers were able to get stable as soon as possible in both positions and in four direction (p=0.001).

Conclusion: Athletes in sudden perturbation want to reach equilibrium and stability in shorter time by increasing speed CoP. Thus it seems, time to stability can be a good indicator for balance evaluating.