IRCT201109196767N1 IRCT 2011-10-12 Shiraz University of Medical Sciences The effect of ankle muscle fatigue on postural control and muscular activation patterns The effect of plantar flexor muscle fatigue on postural control and muscular activation pattern during external perturbation in healthy students (20-35 Y/O) of Shiraz Rehabilitation School 2011-10-22 anticipated 15 Complete https://irct.ir/trial/7178 interventional Randomization: N/A, Blinding: Not blinded, Placebo: Not used, Assignment: Single, Purpose: Prevention. N/A Normal subjects. Intervention 1: External perturbation (expected and unexpected): Subjects expose to a rapid loading in to the right palm (25% of body weight) from 20 cm obove his/har right palm, while the shoulder is in 90 flexion. In expected condition the subjects are aware of loading time (3 seconds after the beep sound the loading will occure). But in unexpected condition the subjects do not any thing about the loading time. Intervention 2: Making the plantar flexor muscles fatigued: The person sitting on the bed with the thigh and leg on the it. One end of the load cell strap will be fixed to the bar behind the person and the other end will be fixed below the ankles. The maximum voluntary contraction of both flexor muscles will be evaluated using the electrical load cell. Then, 60 percent of this amount is applied to fatigue the muscles; The person will asked to apply pressure to the strap while maintain 60 percent of his/her maximum voluntary contraction by looking at the bar scale on the monitor until feel fatigue. When the bar scale is in green territory the person would maintain the contraction. But if it is in red territory and last for 5 seconds it assumes as fatigue.