The repeatability of posturographic measurements and the effects of sleep deprivation.

The repeatability of posturographic measurements and the effects of sleep deprivation on them were investigated in 23 volunteers over a period of four months. Postural stability was studied by evaluating body sway velocity and the maximal and average vibration-induced shifts of the centre of pressure in the anterio-posterior and lateral directions. The posturographic test was performed with and without exposure of the calf muscles to vibration. Subjects were tested both with their eyes open and closed, and the measurements were performed weekly during the first month and once every month thereafter. The interindividual results differed more than the intraindividual ones, indicating that posturographic measurements are most suitable for functional monitoring in one person's tests. The dispersion of the results did not diminish with time, nor did the body sway decrease. The findings suggest that no learning takes place in nontrained persons. In the second part of the research, measurements were performed twice after the subjects had been awake the previous night or 24 hours. Postural stability did not deteriorate in this situation.