Trunk balance is essential for physical stability, but traditional assessment tools, such as force plates and 3D motion capture systems, can be inaccessible or unsafe for patients unable to stand. This study introduces a seated trunk balance training and assessment system that combines a tilting chair with an Inertial Measurement Unit (IMU). The system features a kinematic design that transmits the user's trunk movements to the chair's seat, allowing for quantitative measurement without the need for body-mounted sensors. A pilot study was conducted to evaluate technical feasibility by comparing a seat-mounted sensor (CS-IMU) with a reference sensor (T12-IMU) attached to the T12 vertebra. Assessment items included Range of Motion (RoM), rotation accuracy, and agility. Results indicated a very high correlation for lateral bending (r = 0.958) and rotation phase angle (r = 0.990), while flexion/extension showed a moderate correlation (r = 0.691). Additionally, agility tasks demonstrated consistent results in the lateral direction (r = 0.806). These findings suggest that the proposed system can effectively quantify multi-dimensional trunk movements in a seated position, making it a valuable tool for high-risk populations, such as patients recovering from acute stroke or spinal cord injuries.

In this study, an insole-type ground reaction force (GRF) measurement system using a load cell was manufactured and configured as a system that can measure joint angle and GRF, when walking in conjunction with a commercialized inertial sensor. The data acquisition device was used to acquire synchronized data, between the inertial measurement unit (IMU) sensor and the load cell insole. A three-dimensional motion analysis system comprising six infrared cameras and two ground reaction forces, was used to check the accuracy of the gait measurement system, comprising an inertial sensor and a load cell insole. The motion and force data were acquired while performing five times six-meter walking test by five young adult male subjects (Age: 26.0±1.8, Height: 171.4±6.8 cm, Weight: 62.2±10.8 kg). It was measured and as a result of comparing the calculated sagittal joint angle with the vertical GRF, the sagittal lower extremity joint angle correlation coefficient (Pearson’s r) was 0.40 to 0.94, and the vertical GRF to be 0.98 to 0.99. It is necessary to upgrade the joint angle calculation algorithm through future research. Additionally, the possibility of clinical application for actual stroke patients will be reviewed.