## 3 Data Analysis
### Gait Features Extraction  
In the present work, we exploit data from the signal segment that corresponds to the straight-line walking of the mTUG test and the WST test, when the latter is executed in Slow, Normal and High speeds. Specifically, two recordings per test were analyzed for each participant. The distance of straight-line walking is 10 m \(\pm\) the distance that corresponds to one step, since some participants turned slightly before or slightly after the marked 10 m aisle. This fluctuation has a small influence on the estimated values of the spatial features when the range of step counts (14.35-22.48) is considered (see Table 4). To verify this, we performed a cross-check by adding or subtracting one step, on our calculations. We observe that such a fluctuation results in modifications to the estimations restricted to the second decimal place. The estimated temporal and spatial gait characteristics (18 in total) are presented in Table 4 for the different participants groups, i.e., Adults (S), Elderly (EL), PD patients (PD). Table 5 shows the relevant features for the PD group of participants in relation to the ON and OFF medication states, whereas Table 6 presents those for the PD group of participants relative to their Severity Level, estimated using the MDS-UPDRS: Part III. The results are presented as mean values together with standard deviation, rounded to two decimal places. For the analysis of the collected data, we firstly extracted and examined the spatial and temporal gait characteristics of all different participant groups on WST-Slow, Normal, High and the mTUG tests, as shown in Table 4. Participants were instructed to perform both the WST-Normal and the mTUG tests using a normal walking rate. However, we retained the tests' data separately so that it would be feasible to conduct future comparative studies and to examine the effect of prior physical activity that is noted in the mTUG test (rising from a chair with arms crossed on the chest). Normal gait speed, in terms of comfort, has been reported to be approximately 1.30 m/s for adults of 60 years [50], approximately 1.20 m/s and 0.95 m/s for the elderly aged between 70-79 years and 80-99 years, respectively [51], while for PD patients with a mean age of 65 years, normal gate speed has been reported to be approximately 0.95 m/s [52]. In our work, the control groups (S and EL), and PD group both have a mean age of 60 years, and we recorded an average gait velocity of approximately 1.22 m/s and 0.97 m/s, respectively. In the mTUG test, we observed an increase in gait velocity for all groups, although they have been instructed to employ a normal pace of walking (as in WST-Normal test). Examination of the estimated features on the different groups and tests shows that different speeds of gait affect the results. Particularly, for all groups of participants, as we move from WST-Slow to Normal and to High tests, and therefore the gait velocity of participants increases, we observe that all temporal characteristics decrease, while the swing phase (%) and the spatial characteristics increase (Table 4). We observe a similar behavior when the results from WST-Slow to the mTUG tests are examined. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Type of Test** & \multicolumn{2}{c}{**WST-Slow**} & \multicolumn{2}{c}{**WST-Normal**} & \multicolumn{2}{c}{**WST-High**} & \multicolumn{2}{c}{**mTUG**} \\ \hline
**Severity Level \({}^{*}\)** & **Mild** & **Moderate** & **Mild** & **Moderate** & **Mild** & **Moderate** & **Mild** & **Moderate** \\ \hline
**Number of Recordings \({}^{**}\)** & **64** & **60** & **66** & **60** & **66** & **60** & **64** & **60** \\ \hline Left Step Duration  
The Walk Ratio is excluded from this observation. The Walk Ratio is known to be constant at approximately 6.5 \(\pm\) 0.8 (mm/step/min) for healthy adults and for those with pathological gait should decrease [53]. This is indeed observed in our results since the PD group has lower values when compared to those of the control groups, in all different tests.