A proximity sensor for the measurement of the inter-foot distance in static and dynamic tasks

Measuring the base of support is of paramount importance in determining human stability during gait or balance tests. While wearable inertial sensors have been successfully employed to quantify numerous gait parameters (velocity, stride length, etc), they could not be used to estimate quantities related to the feet relative position. Thus, alternative technological solutions need to be investigated. Some attempts have been made by combining light intensity infrared or ultrasounds sensors with inertial measurement units. Lately, the Infrared Time-of-Flight technology (IR-ToF) has become popular for measuring distances. IR-ToF sensor measures the time an electromagnetic wave needs to travel a distance. The aim of this work was to investigate the feasibility of the use of an IR-ToF sensor for estimating the inter-foot distance (IFD) in both static and dynamic tasks. Very accurate IFD estimates were obtained during Static (MAE%=3.3%) and Oscillation (MAE%=4.1%) conditions, while larger errors during Gait trials (MAE%=19.8%).