Key factor in joint force calculations in running: the estimation of centre of pressure using one wearable sensor
Robbert P. van Middelaar (EEMCS-BSS), Jasper Reenalda (EEMCS-BSS)
Abstract
INTRODUCTION: Running has a high incidence of overuse injuries, presumably caused by either high or repetitive loading during running. Estimating forces in lower extremity joints can provide insight into this repetitive load during landing, and subsequently in potential injuries. Inverse dynamics is a common non-invasive method to calculate joint forces based on the measured body movements and external forces applied at the foot during ground contact. To perform inverse dynamics, the distance from this external force to the ankle joint, the Centre of Pressure (CoP), is essential. However, CoP is only measurable with lab-based force plates or expensive pressure insoles. This study aimed to quantify CoP with only one wearable sensor (inertial measurement unit (IMU)), thereby enabling to estimate joint forces with an easy-to-use sensor setup.
METHODS: 7 subjects ran on treadmill at 9, 11, and 13 kph. Reference CoP was obtained from a force plate and lower leg orientation from an IMU. CoP was estimated by projecting the horizontal distance between Centre of Mass (CoM) of the lower leg relative to the ankle, based on the lower leg orientation and CoM distance to the ankle.
RESULTS: Mean RMSE between the CoP estimate and reference was 1.82±1.62, 1.80±1.65, and 1.84±1.68 cm at 9, 11, and 13 kph, respectively, during 25-75% of ground contact. Pearson correlation was 0.98 for all speeds.
CONCLUSION: This method shows potential for calculating CoP using only one IMU, potentially providing insight into joint forces and injuries with an easy and user-friendly setup.