## 4 Discussion
They observed a reduced peak distance (by 16%) between COP and COM at the phase of gait initiation where the COP moves anteriorly under the stance foot [33]. [PERSON] et al. [33] suggested that a smaller COP-COM distance may be a conservative strategy adopted by IPD to reduce the mechanical and postural requirements and the magnitude of muscular strength required at this phase. The only point in the gait cycle that demonstrated a marginally significant difference between groups regarding U\({}_{\text{MAX}}\)-XCOM A/P and M/L was U\({}_{\text{MAX}}\)-XCOM A/P at FDS and MS (Table 4). At MS, the CON group demonstrated a distance between U\({}_{\text{MAX}}\) and XCOM in the A/P direction that was 67.07 mm less than the PD group. This finding may indicate that the PD demonstrated a wider BOS in the A/P direction during the turn, which is not typically seen in this population as it is more typical to see a narrowed BOS. One explanation for this finding may be that the visual cues (cones and force plates) provided during the turning task may have altered typical gait and turning patterns in the PD group. Additionally, an increased anterior XCOM owing to more forward-flexed postural alignment in IPD may have decreased the time spent in the less stable phases of gait during turns, FDS, and MS. Further research is needed to characterize this variable and the clinical relevance of U\({}_{\text{MAX}}\)-XCOM A/P at MS and FDS as a parameter of dynamic balance control during gait and 90\({}^{\circ}\) turns in IPD. With regard to U\({}_{\text{MAX}}\)-XCOM M/L, one previous study observed that individuals with mild/moderate PD during 30-180\({}^{\circ}\) turning had a narrower BOS than healthy controls, which led to a reduced mean distance between the XCOM and the BOS, indicating some dynamic instability [14]. A reduced mean distance between U\({}_{\text{MAX}}\) and XCOM in the M/L direction was expected in the present study based on this previous research finding. Based on our findings, the mean distances between U\({}_{\text{MAX}}\) and XCOM in the M/L direction were larger in the CON group than in the PD group, although these differences were not statistically meaningful. [PERSON] et al. [17] suggested that a greater distance between XCOM and BOS may be an adaptation for unsteady walking and is associated with increased M/L stability during walking. Although statistical analysis of primary and secondary variables showed minimally significant group differences across the data in this study, the application of 3D motion analysis of walking with turns may be clinically relevant. Completing turns during gait may be a more challenging task for IPD than straight-line walking as there are demands for coupling between gait and postural control as the individual modifies the locomotor pattern in this postural transition [13]. Three-dimensional motion analysis can be used to examine changes in dynamic balance over time in IPD to track disease progression and associated dynamic stability changes, which might provide insight into fall risk. This type of dynamic movement analysis during turns and other gait tasks is salient to daily ambulatory functional activities and balance demands in IPD. Since IPD are at high risk of falls, it is important to understand the changes in dynamic balance and MOS measures that are related to falls. On the other hand, the clinical application and utility of 3D motion analysis for fall prevention in the examination and treatment of IPD are limited due to the need for specialized equipment and time for complex data processing. While this research regarding the utility of the MOS in IPD is mechanistic and exploratory in nature, it can offer insight into dynamic balance variables to investigate potential differences between healthy elderly and IPD that may be associated with an increased risk of falls.