Estimation of vertical walking ground reaction force in real-life environments using single IMU sensor

Monitoring natural human gait in real-life environments is essential in many applications, including quantification of disease progression, monitoring the effects of treatment, and monitoring alteration of performance biomarkers in professional sports. Walking ground reaction forces are among the key parameters necessary for gait analysis. However, these parameters are commonly measured using force plates or instrumented treadmills which are expensive and bulky and can only be used in a controlled laboratory environment. Despite the importance of real-life gait measurement, developing reliable and practical techniques and technologies necessary for continuous real-life monitoring of gait is still an open challenge, mainly due to the lack of a practical and cost-effective wearable technology for ground reaction force measurement. This paper presents a methodology to estimate the total walking ground reaction force GRF_vt in the vertical direction using data from a single inertial measurement unit. Correlation analysis of the vertical acceleration of different body segments with GRF_vt indicated that the 7th cervical vertebrae is one of the best locations for the sensor. The proposed method improves the accuracy of the state-of-the-art GRF_vt estimation by 25%, by utilising the time-varying ratio of the vertical acceleration of the human body centre of mass and measured C7 vertical acceleration. Results of this study showed that the proposed method estimated consistently the GRF_vt in both indoor and urban outdoor environment, with a 4-8% peak-to-peak normalised root mean square error.