Neuromechanical analysis of gait coordination during forward and backward walking

Farivar, Morteza

Item

Neuromechanical analysis of gait coordination during forward and backward walking

Farivar, Morteza

Date

2025-08-05

Abstract

Introduction: Gait coordination reflects the integration of neural and biomechanical systems essential for functional mobility. Parkinson’s Disease (PD) is characterized by gait disturbances that impair both segmental and interlimb coordination, yet the nuanced effects of walking speed and direction on coordination across the lifespan remain poorly understood. This dissertation investigates coordination and control during forward (FW) and backward walking (BW) across different age groups and neurological statuses, with a focus on nonlinear coordination metrics to identify neuromechanical deficits and adaptability constraints. Methods: Three interrelated studies were conducted. Chapter II presents a scoping review of coordination impairments in PD, synthesizing literature on gait-phase synchronization, Phase Coordination Index (PCI), and segmental timing abnormalities. Chapters III and IV detail experimental studies analyzing Continuous relative Phase (CRP) and PCI across young adults (YA), older adults (OA), and individuals with PD during FW and BW at multiple treadmill speeds. Kinematic data were collected via motion capture and analyzed using Visual3D and MATLAB pipelines. Spatiotemporal and coordination parameters were statistically examined through mixed-effects ANOVA models. Results: The scoping review synthesized findings from 14 studies and identified notable gait impairments in individuals with PD, including reduced walking velocity, shorter step length, and limited joint range of motion. Coordination deficits were commonly reflected in increased synchronization delays, abnormal phase shifts, and elevated PCI values, particularly in individuals with freezing of gait. These findings underscore the heterogeneous motor effects of PD and support the need for individualized assessments. In the experimental studies, faster walking improved segmental coordination (CRP) and bilateral limb phasing (PCI), particularly during mid-stance and swing transitions. These adaptations aligned with the theoretical framework of Dynamical Systems Theory, suggesting that speed functions as a control parameter to promote stable coordination patterns. In contrast, individuals with PD exhibited elevated CRP and PCI values across all speeds and in both walking directions, indicating reduced adaptability and impaired neuromechanical control. The effect of BW further amplified these impairments, with pronounced segmental desynchronization and temporal instability. Spatiotemporal patterns in PD—including prolonged stance time and shorter step length—suggested bradykinetic constraints that limited the motor system’s ability to adapt coordination patterns effectively. Conclusion: These findings underscore the clinical utility of CRP and PCI as diagnostic tools, as both metrics sensitively captured phase-specific deficits in segmental and interlimb coordination that were not evident from traditional spatiotemporal data alone. Specifically, CRP revealed impaired segmental coordination and diminished intralimb adaptability in PD—particularly during BW—while PCI detected persistent bilateral timing disturbances resistant to speed modulation. The consistent elevation of these coordination indices in PD, even when step length and walking speed remained comparable across conditions, suggests their potential for detecting latent neuromotor impairments. Thus, CRP and PCI offer mechanistically informative markers of gait dysfunction that extend beyond descriptive parameters, supporting their integration into clinical assessments to guide individualized rehabilitation targeting dynamic motor control.