## 4 Discussion
### Multidimensional Postural Control: Neurobiomechanical Integration of Findings  
Persistent post-stroke PC dysfunction can be partially attributed to disruptions in both structural and functional brain pathways. These disruptions often result in an imbalance between the dorsolateral and ventromedial systems [163], leading to impaired voluntary movement--especially on the contralesional side--and bilateral PC deficits, with greater impact on the ipsilesional side [164; 165]. In this study, all participants had lesions in the MCA territory, the most affected region following stroke [166]. Such lesions may compromise neuronal flow between motor area six (including the premotor cortex and supplementary motor area) and the reticular formation, particularly affecting the corticoreticular (CRS) and corticospinal (CSS) systems [4]. This disruption impairs the neuronal networks responsible for the interaction between CoP control and joint amplitude regulation [90; 167], as reflected in our findings. Clinical assessments, including the Mini-BESTest and FMA-LE, revealed significant impairments in both anticipatory and reactive PC, as well in LL motor function. These findings are consistent with biomechanical evidence of altered CoP dynamics and joint amplitudes during GI. Although no formal correlation analysis was conducted, the observed association between lower clinical scores and impaired biomechanical performance highlights the interdependence of neural, motor, and postural systems [2; 168]. The CRS system provides both structural and functional connections between the cerebral cortex and the spinal cord. It plays a key role in CoP control by generating APAs essential for stabilizing the COM before movement [169]. Dysfunction in the CRS appears to compromise CoP stability, particularly in the ML direction, as evidenced by an increased CoP magnitude of variation, lower LyE, and reduced MSE. These patterns reflect limited neuromuscular flexibility and a reliance on rigid compensatory strategies [99]. Similarly, the CSS, which also originates in motor area six, is essential for accurate movement execution, particularly in distal segments [170; 171]. The shared cortical origin of the CRS and CSS helps explain the close relationship between posture and movement control [172; 173]. Damage to these pathways leads to irregular joint amplitudes, exaggerated FLE-EXT movements in the sagittal plane, and increased rotational patterns in the transverse plane, further highlighting impaired segmental coordination [174]. As a result, individuals rely more on proximal joints to compensate, producing inefficient and exaggerated movement patterns during GI [175]. Although the VSS is primarily associated with brainstem function, lesions in MCA can indirectly affect its role in PC by disrupting cortical regions such as the premotor cortex, SMA, and posterior parietal cortex [90]. These areas are responsible for integrating the vestibular, somatosensory, and visual inputs essential for postural stability [89]. The interplay between the CRS, CSS, and VSS is critical for modulating both reflexive and APAs. Disruptions in these pathways destabilize the COM and impair segmental coordination [90]. During dynamic tasks such as GI, compensatory reliance on the VSS often exposes its limitations, exacerbating postural instability. This is further aggravated by anterior displacement of the head's COM--frequently observed in stroke survivors--which alters biomechanical alignment and increases reliance on compensatory flexor muscle activity [89; 174]. Ultimately, the shared neural circuitry of posture and movement highlights the close interdependence between CoP dynamics and joint amplitude control [169; 176]. Motor area six, encompassing the SMA and premotor cortex, functions as a central hub for coordinating both postural adjustments and voluntary movements [90]. Dysfunction in these region delays APAs and disrupts multi-joint coordination, leading to an increased dependence on reactive adjustments and reduced movement efficiency [174].