Body sway measured by force platform is an excellent simple test for diagnostics of locomotory, balance, visual and neural disorders. In this study the body sway parameters have been measured on a group of healthy medical workers in the morning/evening time before/after their work day. The centre of pressure (CoP) trajectories in a series of different 2-leg stances and during a step forward off from the force platform have been recorded. It was found, in the morning the sway amplitudes were higher due to relaxed state of muscles, while after the work day the muscles were tired and the force platform test demanded more attention and body control which mostly lead to lower body sway amplitudes. The step off from the platform were executed faster in the evening, and the more elderly individuals exhibited more pronounced pathological signs in the CoP trajectory in the evening. Basing on the data analysis, new indices of tiredness and stress level are proposed for occupational medicine.

Keywords: body sway, posture balance, control, medical diagnostics, stress, tiredness