Effect of Change of Direction (COD) Movement on Plantar Pressure and Foot Balance in Bilateral Limbs

This protocol establishes a standardized approach to test whether a 45° change-of-direction (COD) task elicits asymmetrical plantar loading between dominant and non-dominant limbs. The workflow includes pressure-plate calibration, barefoot participant preparation, and approach-speed control at 3.5 m·s⁻¹ (±5%) using timing gates to improve trial consistency. Plantar loading is quantified using ten-region foot segmentation, and stance is time-normalized to 101 points. Force trajectories are normalized to the average vertical force (Zavg), enabling between-limb comparison of time-continuous signals. Limb differences are evaluated using one-dimensional Statistical Parametric Mapping (SPM1d) with random field theory-based inference, complemented by discrete summary metrics (e.g., regional peaks and foot balance indices) as needed. In a cohort of 15 healthy adults performing standardized 45° COD trials, time-continuous analyses did not reveal curve-level statistical significance between limbs, indicating a high degree of functional symmetry under the present conditions. Although small directional tendencies were observed in some plantar regions, these should be interpreted as descriptive rather than definitive limb-specific strategies. Overall, the protocol provides a transparent and reproducible framework for bilateral plantar mechanics research, supporting applications in sports performance testing, footwear evaluation, rehabilitation monitoring, and clinical gait assessment.