## 4 Discussion
### CoP Dynamics  
PC integrates sensory systems, the CNS, and the musculoskeletal system to support both postural maintenance and movement execution, ensuring stable posture and correct segmental orientation during tasks like GI [89; 90]. Despite some metrics not reaching statistical significance, the increased magnitude of variation and reduced stability and complexity observed in CoP measures suggest critical dysfunctions. Figure 12 highlights the CoP parameters that showed statistically significant differences between the stroke and healthy groups, emphasizing key impairments in postural control. The linear analysis revealed significant increases for the stroke group in ML TDISPL and MDISP, paired with decreased AP-MVEL. These findings suggest greater postural instability, particularly in the ML direction, during preparatory phases of movement, essential during GI [50; 91; 92]. Higher ML variation aligns with previous findings showing that stroke survivors have difficulty stabilizing the COM in the ML direction--a key factor in fall prevention [50; 93; 94; 51]. This may result from multiple stroke-related impairments, such as altered muscle activation, asymmetric lower limb weight distribution, exaggerated trunk APAs, dysregulated CoP/COM control [16], greater visual dependence, and deficits in the integration of visual, vestibular, and somatosensory information [93; 95]. Complementing the linear findings, the non-linear analysis revealed a reduction in entropy and LyE measures in the stroke group. These reductions reflect the diminished system complexity and adaptability, which are critical for responding to both predictable and unpredictable environmental demands [6; 28]. In particular, the marked reduction in ML-CoP POS LyE in the stroke group highlight a disrupted interplay between motor stability and flexibility during dynamic perturbations [38]. This often leads to the emergence of more rigid motor patterns, resulting in more consistent and repetitive sway behaviours, especially in the ML direction [96]. These findings are consistent with the previous literature reporting increased regularity in the temporal structure of CoP variability among stroke survivors, particularly in the ML direction [38; 97]. Such regularity has been interpreted as a compensatory mechanism in which the PC system adopts less flexible motor strategies to cope with reduced adaptability [6; 98; 99]. These rigid strategies may explain the impaired CoP dynamics observed during the feedforward phase of GL, where reduced adaptability limits the ability to adjust, explore, and adopt alternative, more efficient motor strategies to meet the task demands [100]. Decreased MSE values further supported this interpretation, indicating lower complexity and adaptability in PC system. This aligns with the study by [PERSON] et al. [97], who reported reduced complexity in stroke survivors early in recovery. Altogether, the findings suggest that stroke-related motor system dysfunction impairs the capacity to respond to perturbations during the preparatory phase of gait initiation--supporting the hypothesis that reduced complexity correlates with diminished adaptability [35; 99]. This interplay between instability and compensatory is a well-documented hallmark of post-stroke motor dysfunction [101]. The observed reduction in AP-CoP MVEL in the stroke group suggests slower feedforward control, likely reflecting motor impairments and reduced APA efficiency [91]. This is consistent with evidence that stroke survivors exhibit diminished APA velocity due to neural reorganization dysfunction [50; 91; 92]. This trade-off between stability and  
Figure 12: Statistically significant results of linear and non-linear CoP analysis between healthy and stroke groups. Symbols indicate the type of significance: *: significant linear differences; *: significant non-linear LyE differences; *: significant non-linear MSE differences. movement efficacy has been documented, as reduced AP momentum can compromise functional mobility [102].