Balance Assessments
fatigue
Balance performance was measured while subjects stood on the right leg. The sway path was assessed while subjects stood on solid ground, while balancing on a soft mat (Balance-pad, Airex), and while standing on a balance wobble board (Kübler Sport; 37*9 cm; radius of sphere 13.4 cm; height of sphere: 7.8 cm). The overall sway path length (in millimeters) was measured in all conditions using a force plate (Leonardo Mechanograph GRFP LT; Novotec Medical, Pforzheim, Germany). The sway path length is defined as the common length of the trajectory of the center of pressure and was calculated as the sum of the point-to-point Euclidean distances. All balance assessments were accomplished according to standard operating procedures established in our laboratory. We recorded 3 trials per device with a duration of 20 seconds. Subjects were asked to rest for 10 seconds between 2 trials. No rest was given between the conditions. The resting time was minimized because measurements were to be performed in a short time after the fatigue protocol.