Kinematic parameter evaluation for the purpose of a wearable running shoe recommendation

We present a system capable of computing two major kinematic parameters that are necessary for a running shoe recommendation. The system consists of one inertial measurement unit located in each sole of a pair of running shoes. This unobtrusive integration allows for a long-term and objective assessment of the strike type and the pronation of the foot, which can be characterized by the sole angle and the range of motion respectively. An algorithm for computing these parameters is presented, which includes a sensor to shoe alignment, a step segmentation and a quaternion based angle calculation. A study including 5112 ground contacts from 27 subjects was conducted to evaluate the accuracy of the presented algorithm. The best results compared to a motion capture system can be achieved with a subject dependent sensor to shoe alignment with a mean absolute error of 2.8° ± 2.5° for the sole angle and 2.0° ± 1.9° for the range of motion.