Study on estimation of peak Ground Reaction Forces using tibial accelerations in running

Ground Reaction Forces (GRF) are exerted by a surface as a reaction to a person standing, walking or running on the ground. In elite and recreational sports, GRFs are measured and studied to facilitate performance improvement and enhance injury management. Although, GRFs can be measured accurately using force platforms, such a hardware can only operate in a constrained laboratory environment and hence may limit and potentially alter a subject´s natural walking or running pattern. Alternatively, a system that can measure GRFs in a more natural environment with less constraints can provide valuable insights of how humans move naturally given different gait patterns, terrain conditions and shoe types. In this regard, inertial Micro-Electrical-Mechanical-Sensors (MEMS), such as accelerometers and gyroscopes, are a promising alternative to laboratory constrained data collection systems. Kinematics of various body parts, such as their accelerations and angular velocities, can be quantified by attaching these sensors at points of interest on human body. In this paper, we investigate the relationship between the vertical GRF peaks measured by an OR6 series AMTI force plate, and accelerations along the tibial axis measured by a MEMS sensor. Our measuring system consists of two low-power wireless inertial units (ViPerform), containing one tri-axis accelerometer placed on the medial tibia of each leg.We investigate the accuracy of the measured and estimated GRF peak in 3 subjects, by means of the Root Mean Square Error (RMSE). The RMSE achieved across the speeds of 6, 9, 12, 15, 18, 21km/h and sprinting were 157N and 151N for subject 1, 106N and 153N for subject 2, and 130N and 162N for subject 3 for the left and right legs respectively. We achieved normalized errors of 6.1%, 5.9% and 5.4% for all the subjects.