Fig. 4From: Validation of wearable visual feedback for retraining foot progression angle using inertial sensors and an augmented reality headsetTransverse caudal view of the feet, illustrating the calculation of the foot progression angle for the right foot. The foot progression angle (θFP) of the ith step is derived from the difference of foot vector (rf) and heading vector (rw). The latter two vectors are computed based on the positions of the heel (ph) and toe (pt) as illustrated in the figureBack to article page