Keeping the foot dorsiflexed and the leg straight, the foot should be swung forward and then quickly returned to the running surface. The hips should be propelled forward as the foot pulls the ground backward. Once the walking action is mastered, the athlete should proceed to a straight leg bounding action. The bounding will allow for the development of greater negative forces with each landing. This drill is done one leg at a time while jogging slowly.
Forward speed is unimportant, but leg speed in the drill is critical.
Simply, while jogging, move one leg rapidly through one full cycle and back to the ground. Start by doing just one cycle with one leg, jog a few more strides and then do the other leg. After learning this movement, progress to where you can do four in a row with one leg while maintaining a slow jogging motion with the other leg. This drill takes the leg quickly through a full range of motion. While on a recovery jog between intervals, throwing in a couple of these will help stretch the leg muscles.