Biomechanical Evaluation of a Biomimetic Stand-Assist Toilet Seat in Older Adults: A Synchronized AI-Kinematic and Kinetic Analysis

Modern residential toilets pose a significant biomechanical challenge for older adults with diminished muscle strength, as standard seat heights necessitate excessive joint range of motion (ROM) and compensatory upper-limb reliance. This study evaluated the biomechanical efficacy of a biomimetic Stand-assist Toilet Seat designed to facili-tate sit-to-stand (STS) transitions through a proactive curvilinear trajectory. Thirty community-dwelling older adults were stratified into high-, moderate-, and low-functioning groups based on 30-second Chair Stand Test normative data. A mul-ti-modal assessment framework was employed, integrating MediaPipe-based AI pose estimation for joint kinematics and instrumented armrests with high-precision load cells for kinetic analysis. The results demonstrated that the biomimetic seat signifi-cantly optimized movement efficiency, evidenced by a robust reduction in hip and knee ROM with a large effect size (η²p > .70, p< .001). Kinetic data further revealed sub-stantial upper-limb unloading, with significant decreases in peak arm-support force (Fmax,p=.001, η²p =.35) and cumulative impulse (Iarm,p< .001, η²p =.42). While no signifi-cant interaction was found, a clinical trend (η²p =.17) suggested that low-functioning individuals derived the greatest mechanical advantage from the device. By actively guiding the user’s center of mass toward a biomechanically advantageous "power zone," the biomimetic trajectory minimizes compensatory trunk flexion and armrest reliance. These findings provide evidence-based insights into the role of trajecto-ry-informed assistive technology in enhancing toileting safety and functional inde-pendence for the aging population, particularly those exhibiting signs of possible sar-copenia.