Custom Wearable Motion System for Human Gait Biomechanics Analysis in Hypogravity Environments

Introduction
Understanding the impact of hypogravity on human gait characteristics is crucial for upcoming space exploration missions. Ground reaction force (GRF) and joint kinematics are critical gait parameters for assessing human locomotion. Traditional methods, such as force plates and motion capture systems, have been widely used to study GRF and joint kinematics under different walking speeds and inclines in normal Earth gravity. However, these methods are often complex, time-intensive, and require elaborate setups. While wearable sensing systems offer a simpler method and effectively track human walking motion, their application to analyzing human kinetics and kinematics in hypogravity environments has not been fully explored. To address these gaps, we propose a wearable motion sensing system that integrates a custom-designed force insole, tailored to different gravity levels to measure GRF, and inertial measurement units (IMUs) to track lower limb joint kinematics. This system was employed to evaluate human gait characteristics and kinematics under simulated hypogravity conditions, combining GRF and joint kinematics for a comprehensive analysis.

Methods
We first developed a mechanical suspension platform capable of simulating adjustable hypogravity conditions for level walking experiments. Our wearable motion sensing system comprises four IMUs and a custom force insole, enabling the real-time monitoring of lower limb joint acceleration, angular velocity, Euler angles, and GRF during hypogravity walking experiments.

Results and Conclusion
The wearable motion sensing system successfully monitored lower limb joint kinematics and GRF simultaneously, revealing new kinematic characteristics during hypogravity walking. The custom force insole accurately captured GRF trends under these conditions. This system provides a robust tool for investigating gait characteristics and human kinematics in hypogravity environments, offering insights into optimizing mobility strategies, enhancing wearable device design, and understanding biomechanical adaptations under such conditions.