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

Summary

This protocol details a standardized approach to quantify plantar pressure distribution, foot balance, and foot axis angle during 45° change-of-direction tasks using a Footscan pressure plate, enabling reproducible assessment of bilateral limb loading patterns at a controlled approach speed.

Abstract

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.

Introduction

Change of direction (COD) movements are key skills in many sports, particularly in high-intensity activities such as football, basketball, and rugby, where speed and precision directly affect athletic performance and competitiveness^1,2. Research has shown that COD movements not only require athletes to possess high levels of lower limb strength and explosiveness but also demand good coordination and fine gait control^2,3,4. To gain a comprehensive understanding of the biomechanical mechanisms underlying COD movements, ....

Protocol

The study has obtained approval from the Ethics Committee of the Research Institute at Ningbo University (Approval Number: ty2022020). All participants provided written consent, having been informed about the purpose, requirements, and procedures of the experiment. The equipment and software used are listed in the Table of Materials.

1. Laboratory preparation

A Footscan 2-m pressure plate (2.0 m × 0.40 m × 0.02 m, 16,384 sensors) was used and sampled at 480 Hz. The plate was embedded flush with the surrounding runway using protective mats to eliminate step-height artifacts. The sys....

Results

Force and pressure time-varying changes in the ten regions

During change-of-direction movements, the dominant foot exhibited higher time-series force and pressure values than the non-dominant foot across most plantar regions (e.g., M1, M3, M4, MF, and SUM), particularly during the mid-to-late stance phase. However, statistical parametric mapping (SPM) analysis revealed that these differences did not reach the threshold for statistical significance (α = 0.05). For instance, in .......

Discussion

This study explored bilateral differences in plantar pressure distribution and foot balance during a standardized 45° COD task. Overall, the time-continuous SPM1d analyses did not identify any statistically significant between-limb differences in regional force/pressure trajectories across stance. Although the dominant limb showed slightly higher magnitudes in some regions and the non-dominant limb showed the opposite tendency in others, these patterns should be interpreted as descriptive, non-significant tendencies.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
A Foustcan 2-m pressure plate	Tekscan Inc., USA	5101
Data acquisition software	Tekscan Inc., USA	www.tekscan.com/products/software
Infrared timing gates	Lafayette Instrument Company, USA	5016A
MATLAB	MathWorks, USA	www.mathworks.com/products/matlab
SPM1d toolbox	Open-source (Statistical Parametric Mapping)	www.spm1d.org