Assessing Center of Mass Estimation in IMU-Based Systems: A Comprehensive Analysis of Dynamic and Static Motion

Tracing the three-dimensional (3D) trajectory of the body's center of mass (CoM) provides valuable insights into the mechanics of motion. With the advancement of technology, new systems are emerging into the field of biomechanics with the capability of providing human CoM estimations. However, the recently popularized inertial measurement unit (IMU) based systems have not been fully validated in terms of their capability to provide reliable CoM estimations. To this purpose, in this study, we present a comprehensive evaluation of one of the most widely used IMU systems in comparison to a traditional force plate-based CoM estimation technique. The study included five participants who performed several in-place motions and two types of vertical jumps. Our results revealed that the IMU-based system performed poorly in the Full-Squat task while showing better estimations in other tasks. Another important finding is that this system tends to over/under-estimate the CoM position depending on the task performed along specific directions, with the most significant underestimations being observed along the vertical direction for tasks such as Full Squat, Half Squat, Mediolateral and Internal External swaying, while it showed an overestimation in jumping tasks. Researchers need to account for this directional variation in their experimental design and data analysis. To use IMU-based systems in biomechanical research or clinical applications, rigorous validation procedures are required depending on the study's specific needs. Correction factors or calibration techniques should be applied to improve measurement accuracy.