Measuring Ground Reaction Force Using in-Shoe Resistive Force Sensors

Ground reaction force is an important measurement when analyzing the gait cycle. It is typically measured using force plates located on the walking surface. For these force plates to measure ground force accurately, a subject must walk over them and carefully place one foot on a single plate. A more effective way is the use of a double belt treadmill with force plates beneath each belt. In this case, the subject must keep one foot on each belt at all times in order to attain an accurate ground force. Even though this method is more convenient than a force plate on the ground, it still has its limitations. Subjects are unable to measure their ground reaction forces during out-of-lab activities such as outdoor walking or stair climbing. The purpose of this study was to develop an insole force sensor that accurately measures the ground reaction force of the user outside of the laboratory environment. This was done by attaching four resistive force sensors to the bottom of a shoe insert. The four force sensors were placed anatomically so the process can be easily replicated. The subject wore the force sensor insert in their shoe while walking on a double belt treadmill with force plates. The ground reaction force from the treadmill was recorded while the data from the insert force sensors was recorded. A feedforward neural network was trained to convert raw data from the force sensors to actual ground reaction force. Once the insert system was trained, a portable ground reaction force sensor was created and ready to be used outside of the laboratory environment.