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 aligned with peak ankle power generation. This provide evidence that the ankle initially propels the stance limb toward swing in terminal stance and then the hip assumes the role in double support and into swing phase. This observation is further supported by a principle component analysis of the hip and ankle moments (60)