Frequency analysis of body sway in standing posture
Frequency analysis of the sway of the body center of gravity appearing in the upright standing posture is important as one of the measurements in stabilometry. However, although analysis using the FFT method is now widely used, it is difficult to interpret the results. Therefore, using MEM method, we made a scatter diagram showing the frequency on the x-axis and the spectral peak area on the y-axis. In the scatter plot, we filled in the power law distribution curve and the approximate
... proximate expression. This diagram (the peak-area spectrum) was the object of this study. The results obtained were as follows. 1) In healthy cases, the area spectra showed the power law distribution. 2) In a case with labyrinthine failure, the spectrum showed an increase of the area of the maximum peak frequency. We considered the finding is caused by a disorder of the labyrinthine righting reflex. 3) In a case with cerebellum disturbance, irregularities were observed in the power law distribution of the peak areas. The findings are interpreted as due to a coordination disorder in standing posture regulation. 4) In a case of Parkinson's disease, the slope of the power law distribution curve became flat. The findings are interpreted as due to postural control disorder caused by muscle rigidity. Examination of the peak area spectrum is useful for quantitative assessment of the body sway in an upright standing posture.