Fig. 1.

Spectra of a representative PD patient (age: 78 yrs.; disease duration: 7 yrs.; OFF medications) and a healthy control (age: 78). On the left, the un-normalized frequency spectrum is shown. The controls exhibit clear peaks around 1.8 Hz and 3.6 Hz, corresponding respectively to step and stride time. In the PD signal, only a clear peak around 1.5 Hz can be seen. In the normalized frequency spectrum, compared to the control, the spectrum of the PD patient has more peaks with larger amplitude, indicating a less smooth gait