## 4 Discussion
This finding may indicate that it is more likely that a true difference was observed between the PD and CON groups at MS as opposed to this difference being more likely due to random variation. The MS is the most unstable part of the gait cycle because only one limb is in contact with the ground as the other limb progresses in the swing phase. This dynamic balance demand in MS during 90\({}^{\circ}\) turning, coupled with a narrowed BOS typically seen in IPD, may contribute to postural instability. The CON group had a mid-stance COM-COP inclination angle that was 1.556\({}^{\circ}\) greater than that of the PD group. The closer the COM is to the COP, the smaller the COM-COP inclination angle and the reduced chance of a fall. Similar towalking on a balance beam, the closer the COM is to the COP during MS, the more likely it is that the individual will maintain balance. A reduced COM-COP inclination angle in the PD group may reflect a conservative strategy to reduce their fall risk. Additionally, it may suggest that IPD had increased difficulty controlling the COM position in relation to COP as compared to the CON group. As the variable of most interest, further research is warranted to investigate the COM-COP inclination angle at MS to characterize dynamic balance during walking and 90\({}^{\circ}\) turning in individuals with more advanced stage PD. Our finding regarding differences in MS COM-COP inclination angle between IPD and healthy controls is consistent with previous research. [PERSON] et al. [15] reported comparable group differences in peak COM-COP inclination angle when analyzing IPD and controls during 180\({}^{\circ}\) turning while completing the TUG. These researchers reported a difference in sagittal COM-COP inclination angles (0.96\({}^{\circ}\)), with IPD demonstrating a smaller inclination angle than controls. [PERSON] et al. attributed this finding in IPD during turning to either a conservative shortening of steps as a compensatory strategy or unintentional small steps (gait hypokinesia) related to PD pathology triggered during turning [15]. There are notable differences in methodology between [PERSON]'s study and this present study, as [PERSON]'s PD sample included individuals with more advanced disease stages and FOG deficits. Additionally, [PERSON]'s testing was performed during the off-medication times in IPD, and the task was a TUG test involving a 180\({}^{\circ}\) turn. In contrast, the present study examined individuals with mild-moderate PD without FOG symptoms who were tested during on-medication times during gait and 90\({}^{\circ}\) turns. Despite the milder disease stage of the individuals in this present study, the difference observed in the MS COM-COP inclination angle was greater than the findings in [PERSON]'s study. Our data suggest that a difference of 1.556\({}^{\circ}\) observed may be clinically meaningful. Future research is warranted to examine 90\({}^{\circ}\) turning in individuals with more severe PD, FOG, and positive fall history to identify possible dynamic balance control problems. Altered movement of COM in coordination with COP movement may demonstrate dynamic stability changes, and therefore, this relationship may allow identification and quantification of dynamic balance impairments in IPD of varying severity [33]. When examining COP-COM A/P and M/L at FDS, MS, and SD, a marginally significant difference between groups was observed only in the COP-COM A/P variable at MS (Table 4). The PD group demonstrated a distance between COP and COM in the A/P direction that was 31.3 mm less than the CON group. This finding may reflect strategies utilized by IPD to increase stability, similar to the strategy discussed regarding the COM-COP inclination angle, in which IPD bring their COP and COM as close as possible to reduce fall risk. [PERSON] et al. [33] examined peak COP-COM distance at three points of gait initiation to measure dynamic balance control in IPD with varying severity with and without balance impairments.