The weight-bearing leg forms a constant-length side of the triangle with the hip and the stage, assuming that the knee does not flex (change its angle) while it is holding the weight. In consequence, the hip-joint and hip over the weight-bearing leg is highest at the mid-point of the movement, when the leg is straight below along the plumb-line.
The stride can be lengthened by rotating the hips, so that the weight-bearing hip-joint is behind at the end of the stride, when the leg is behind. The unweighted leg can go a little bit further forward with the hip on that side rotated forward.