SUMMARY
Background: The maintenance of postural control is a key component in dynamic physical activity, especially during muscle fatigue and against external forces. Despite many studies in this field, there is no consensus regarding the effects of plantar flexor muscles fatigue on postural control during different postural tasks.Objective: To evaluate the effects of plantar flexor muscles fatigue on postural control during quiet stance and external perturbation in healthy subjects.Methods: Twenty four healthy individuals (20-35 years) participated this interventional study. The foot center of pressure data was measured using a single force platform, and then the postural control parameters, including the center of pressure displacement and velocity in the anterior-posterior and medial-lateral direction and also path length calculated under two conditions; quiet and perturbed stance, before and after plantar flexor muscles fatigue.Results: The statistical analysis demonstrated that mean displacement and velocity of the center of pressure in the anterior-posterior direction and also path length increased after the fatigue protocol in the perturbed condition. However, fatigue had no significant effects on postural control parameters in the quiet standing condition.Conclusion: These results indicated that the effects of muscle fatigue on postural control depend on the difficulty of the task and the relevance of proprioceptive information. The postural control system appears to use distinct control strategies in different situations such as quiet and perturbed stance conditions, and these strategies may be differentially altered by fatigue. In conclusion, due to the potential risk of loss of balance, it is important to take the role of plantar flexor muscle fatigue into account during more difficult postural tasks.