Subjects are instructed to remove their shoes and step onto the forceplates, which have to be covered with tracing paper. Their feet are positioned by aligning the lateral border of the foot with the appropriate height line marked on the forceplates (ie, short, 76 to 140 cm; medium, 141 to 165cm; or tail, 166 to 203cm). The medial maileoli are aligned with the transverse forceplate line and subjects adopted a comfortable amount of forefoot splay. The outline of their feet is traced onto paper to ensure the same placement in subsequent testing sessions. The visual display monitor is adjusted to the subject's eye level. Subjects are instructed not to move their feet and are asked to stand with their arms at their sides throughout the testing procedure. The standard test suite protocol will be administered, consisting of 6 tests, 3 of which are static and 3 dynamic. The static tests require the subject to look straight ahead while standing as still as possible, initially with eyes open, then with eyes closed, and finally focusing on the display monitor using visual feedback to maintain the position of a cursor (representing the subject's COG) within a centrally positioned target box. For each test, data relating to postural sway is recorded for a period of 20 seconds and the area of the sway is calculated and expressed as a percentage of the subject's theoretical limits of stability (LOS). Assuming that movement about the ankle (with a fixed foot position) resembles an inverted pendulum, these limits are defined as extending 6.25 ° anteriorly, 4.45 ° posteriorly, and 8.00 ° to each side, ~2 and delimit the area over which the COG can safely move without changing the base of support.