Detecting Heel Strikes for Gait Analysis Through Higher-Order Motion Flow

In gait analysis, heel strikes are an important and preliminary cue because gait period, step and stride length can be derived accurately by the moment and position of heel strikes. It refers to the heel that first contacts the ground during the stance phase of the walking cycle (Cunado et al., 2003). This chapter use higher-order motion field to detect when and where a heel strikes the floor. When the foot is approaching to strike, its motion status changes from a forward motion to making circular motion centred at the heel. The amount of radial acceleration on the leading foot will dramatically increase when the heel hits the floor. According to this clue, the key frames can be determined by the quantity of acceleration flow within the ROI, and positions can be found from the centres of rotation caused by radial acceleration. Compared with other heel strike detection methods, the temporal template of using acceleration only requires three consecutive frames for processing so it also allows near real-time detection with only a single frame of delay.