Fig. 1
Instrumented Timed Up and Go test and representative spectral-domain of healthy controls and subjects with PD. a Instrumented Timed Up and Go test (iTUG). b Representative anteroposterior acceleration profile (Acc L AP) during the TUG test for a healthy subject. c Acc L AP of a healthy control (blue) and two subjects with PD (black) - note the FOG event and affected turning. d Representative spectral magnitudes of Acc L AP for two healthy controls and two individuals with PD during TUG trials. Note the well-defined magnitude peaks in the frequency domain in trials of control compared with trials of subjects with PD, which show a broader range of dominant frequencies and SPARC (area under the curve). e-j TUG phases were identified using yaw and pitch angles, the following TUG durations are described: sit to stand, walk 1, turn, walk 2, turn and stand to sit and full TUG. k Frequency ratio (FR) of a healthy subject (blue) and two subjects with PD (black), note the predominance of frequency components in the locomotor (green; 0.5–3 Hz) and freeze (red; 3–8 Hz) bands [1]. IMU: Inertial Measurement Unit; FOG: Freezing of Gait. FR: frequency ratio. Data are from representative subjects in b-d and k (left panel); and mean ± confidence interval 95% in k (right panel) and Mean in e-j; nControl = 6; nPD = 31; *p < 0.05