Table 3.

Sensor-based features extracted from the 7MW test.

Feature	Sensor	Description
Duration [s]	Accelerometer/Gyroscope	Total duration of the test
Cadence [steps/min]	Accelerometer	Cadence in the phase of the gait
SD Cadence	Accelerometer	Standard deviation of the Cadence
NJS AP ML V [m] [35,54]	Accelerometer	The Normalized Jerk Score during gait is computed for each step (i.e., between two consecutive heel strikes), then normalized to the step duration, and then averaged across all steps $$NJS=\sqrt{\frac{T^5}{2}{{\displaystyle \int }}_{Tstart}^{Tend}{(\dot{a})}^{2}dt}$$ where T is the duration (Tend − Tstart), a is the acceleration measured in m/s2.
PCI [35,57] [-]	Accelerometer	Phase Coordination Index (PCI). PCI measures gait coordination (i.e., the accuracy and consistency of the phase generation). $$PCI=PhaseCV+100\cdot \frac{\frac{1}{N}{{\displaystyle \sum }}_{i=1}^N\left|{\phi }_i-{180}^{°}\right|}{{180}^{°}}$$ where PhaseCV is the Coefficient of Variation of the Phase. φi is the ith phase, which measures the step time with respect to the stride time assigning 360° to each stride (gait cycle): $${\phi }_i={360}^{°}\frac{h{s}_{S,i}- h{s}_{L,i}}{h{s}_{L,i+1}- h{s}_{L,i}}$$ where hsL(i) and hsS(i) denote the time of the ith heel strike of the legs with the long and short step times, respectively.
Range AP ML V [m/s2]	Accelerometer	Range of the signal
RMS AP ML V [m/s2]	Accelerometer	Root Mean Square (RMS) of the signal, s (it is a measure of dispersion): $$RMS=\sqrt{\frac{1}{N}}{\displaystyle \sum }_{i=1}^N{\left(s_i -m\right)}^2$$ where N is the total number of points of the signal s, and m is the mean value $mean\left(s\right)$
Reg [10] AP ML V [10] [-]	Accelerometer	Step and Stride regularity measured by means of the unbiased estimate of the autocorrelation function of the signal s: $$A_{unbiased}=\frac{1}{N-\left|n\right|}{\displaystyle \sum }_{i=1}^{N-\left|n\right|}{s}_i{s}_{i+n}$$ where N is the total number of points of the signal and n is the phase shift in number of samples. First dominant period (Ad1) of the autocorrelation coefficient is an expression of the step regularity. Second dominant period (Ad2) of the autocorrelation coefficient is an expression of the Stride regularity

ACRONYMS: AP: Antero-Posterior; ML: Medio-Lateral; NJS: Normalized Jerk Score; PCI: Phase Coordination Index; Reg: Regularity; RMS: Root Mean Square; SD: Standard Deviation; V: Vertical.