Introduction: Sensory-motor control and in general gaining balance will be impaired after an ankle injury and in fatigue situations. The aim of this research was to study the effect of exercise-based fatigue on static and dynamic balance in mountaineering athletes who were successful in returning to a suitable level of physical activity after an ankle sprain injury.

Materials and methods: 25 active mountaineering athletes between 20 and 40 years were recruited on a voluntary basis. 12 persons with severe ankle sprain in the past were selected as experimental group and 13 healthy mountaineering athletes were selected as control group. Because balance test measuring was under the influence of evaluation time; fatigue test measurement running on the treadmill was performed in 2 sessions. Changes or fluctuations in the pressure Center or static balance were evaluated by Sharpened Romberg balance test and dynamic balance was evaluated by stability time after side jumping (the first session) and the maximum distance in the balance test Y (second session) were evaluated in the pre-test and post-test immediately after fatigue resulted by running on a treadmill. Data were analyzed using covariance test.

Results: before fatigue condition, there were a few differences between the two groups in stability time while doing side jump test (P<0.014). After the fatigue and in balance test Y and stability time while doing side jump test; there were more differences (P<0.001). In this case, there was a similar increase on static swing in both groups. Fatigue was considerably reduced the static and dynamic postural control of the athletes who had a history of injury. Changes related to fatigue was significant in dynamic postural control in athletes with previous ankle sprain history.

Conclusion: Even after the successful return to sport for athletes with previous damages, abnormalities in sensory-motor control and balance may lead to an increase the risk of ankle re-injury.