Purpose:
This study explored how variations in the curvature of carbon fibre plates embedded in running shoes affect gait symmetry of the lower limbs in well-trained long-distance runners.

Methods:
Sixteen well-trained runners participated in biomechanical testing under two shoe conditions (flat vs. curved carbon plates) using a Vicon 3D motion capture system (Oxford Metrics Ltd., Oxford, UK) and force plates. Symmetry angle (SA) was calculated for joint angles, moments, and stiffness to assess bilateral symmetry. SPM_1d (One-dimensional Statistical Parametric Mapping) was used to compare time-series joint angle data between shoe types. Two-way ANOVA examined peak joint moments and stiffness across limbs and shoe conditions, while paired t-tests assessed SA differences in joint range of motion, peak moments, and stiffness.

Results:
The results showed that curved carbon plate shoes demonstrated better symmetry in peak ankle eversion and external rotation moments, peak knee external rotation moments and abduction–adduction stiffness, and hip rotational stiffness, suggesting that improved load distribution may help reduce the injury risk typically associated with asymmetric joint loading. In contrast, flat carbon plate shoes exhibited superior symmetry in hip rotational angles and knee flexion-extension stiffness, indicating potential advantages in promoting lower limb coordination.

Conclusions:
These findings preliminarily suggest that the geometry of carbon fibre plates significantly influences lower limb biomechanical symmetry and dynamic characteristics, potentially regulating overall gait coordination through kinetic chain interactions. This study offers biomechanical insights to optimise running shoe design and improve performance and injury prevention in long-distance running.