Introduction: The aim of the current study was to measure ground reaction force and center of pressure (COP) during lower extremity perturbation in single leg standing whit knee flexion and extension in healthy subjects, in addition to revealing reliability of the device used for the related perturbation for using another studies, reliability is one of the characteristic of measuring instrument , this indicates that measuring instrument to what extent in the same conditions gives the same results. Materials and method: perturbation device was built firstly, rotational perturbation (trunk and femur rotation on weigh bearing tibia ) were applied to the dominant leg of 13 healthy subjects during single leg standing . Four models of rotational perturbation (external and internal tibial rotation with knee flexion and extension) were applied to the lower extremities to collect ground reaction force and centre of pressure in these subjects. Subjects attached to lower extremity perturbation device and standing whit single leg on force plate. Subjects were then asked to repeat the tests procedure after a week’s interval. Results: The intra class correlation coefficient and Cronbanch's Alpha values during within and between sessions tests for four models of rotational distributions showed the relatively high reliability of these measurements during single leg standing , the intra class correlation coefficient exceeded 0.7 in all dominants. Conclusion: The relatively high reliability of ground reaction force and centre of pressure measurements during four different perturbations of external and internal tibial rotation with knee flexion and extension in healthy subjects suggests that these measurements can be used during single leg standing in future studies.

Purpose: Footwear used by military individuals is essential to be scientifically evaluated during daily activities. This research aims to examine muscular activities while running with rubber’s new boots compared to used boots in men with healthy and pronated feet.
Methods: Twenty-four men aged 20-25 years (12 men in the pronated group, and 12 men in the healthy group) participated in this research using the convenience sampling method. The subjects received two used and new boots. The boots were made of rubber. Electromyography (EMG) data of the dominant limb were collected while running at constant speed. 
Results: The main effect of “boot type” for semitendinosus muscle activity (P=0.018, η2=0.248) during the loading phase and tibialis anterior (P=0.041, η2=0.177) during mid-stance. 
Conclusion: Rubber boots mileage effect on selected muscle activities in men with and without pronated feet. The use of used rubber boots can increase running-related risk factors.