A way to rotate the leg further backwards and contact the ground further under the hips.
The objective of rotating the thigh further is to accelerate the foot before it contacts the ground. The foot needs to be moving at least as fast as the ground is moving under the body. If it is slower than the ground, then running speed will decrease. The primary muscles used the rotate the thigh down and back are the glutes. The rotation will be delayed if the thigh gradually slows its forward rotation before the glutes are activated. To prevent this, the glutes must activate early and suddenly change the direction of the thigh by pulling it down and back. This creates the potential for accelerating the foot and landing under the hips, but the hamstrings must be active too. If the hamstrings are passive as the glutes pull the thigh down, the lower leg will extend, lengthening the leg. This will slow the leg’s rotation and probably force the foot to land ahead of the hips. By keeping the hamstrings active as the glutes pull the leg down, the lower leg will not extend early, and the hamstrings will assist the glutes in accelerating the leg. Maintaining the angle at the knee slightly longer will put the foot on a path to contact further back than if the knee starts to straighten early.