The hip reaches full extension and begins to flex at 50% of the gait cycle. The hip flexor moment produces the hip flexing motion as realized in the hip power generation burst (Figure 4-12, Point I) that continues to increase in magnitude until foot off. This hip power burst (attributed to concentric contraction of the hip flexors) helps propel the lower extremity into swing. Note that the timing of the onset this power generation (50% of the gait cycle) is closely of generation. This aligned with peak ankle power stance provides evidence that the ankle initially propels the hip as limb toward swing in terminal stance and then the phase. sumes role in double support and into swing com This observation is further supported by a principle ponent analysis of the hip and ankle moments (60) swing The hip extensor moment in the second half of in (Figure 4-12, Point decelerates the lower extremity preparation for foot J) that both the hip contact. It is observed swing in late and early mechanisms af and the hip extensor described in the next section knee motion, as will be