Spectral analysis of acceleration (frequency and amplitude) of MD patients at the beginning of treatment (MD) and healthy controls (HC) captured with the vertical axes of the chest-accelerometer.

<p>Mean amplitude values (in au¹; grey and black horizontal resp.) as well as the group centroid frequency (in Hz; grey and black vertical line resp.) for the whole spectrum of walking (1–3Hz) are depicted in Fig 1a, 1b, respectively. ¹arbitrary unit: values are based on g but attenuated due to the computation of the spectrum and the nonstationarity of the data.