The Pro Balance Master system with software version 8 will be used in the study. The Pro Balance Master system is comprised of two 23cm × 46cm dual force plates connected at the midline of the anterioposterior axis by a pin joint. Each force plate is mounted on a pair of symmetrically positioned force transducers. The four transducers measure vertical ground reaction forces, which form the basis of subsequent calculations of center of pressure (COP) and center of gravity (COG) sway angels. All test data are acquired and then stored on a PC.