The last part of the hop is performed by an arching of the low back. Rotational extension is a more advanced motion in which the back arches to one side. The same precise movement occurs in different positions. For example, the small step with the left foot that a right-handed baseball pitcher would take during the wind-up is a rotational extension of the low back to the right. The other examples covered on this page are the backswing and follow through during a golf swing, as well as the tennis backhand, and walking/running. Start with the back kick on a step.
Back Kick on a Step
This is the easiest position to learn rotational extension. You are way better off initially ignoring the legs and emphasizing the spine. With your left foot hanging off the side of the step or book, your pelvis will turn to the left at first, then your left hip will hike up as your right hip is driven into the ground which should make you taller. You will feel a stretch in the belly, and you should feel your back muscles tightening on the left. Practice on both sides until it is pretty easy.
Backhand Tennis, Follow Through Golf Swing on a Step
Alternating Back Kick
The key here is two-fold. First, be sure that as the right leg goes behind you, the muscles on the right side of the low back are tight. Second, emphasizing driving the front get into the floor, which should cause a stretching feeling on the belly. Only progress when you can do this properly. If you are not getting the hang of it, go back to the back kick on a step.
This is not the backswing golf, it is only the low back part of the backswing in golf. If you are right handed, the backswing golf is the same as the backpack with the left leg. What makes this interesting is that as you take the backswing, at first your center of gravity will shift to the right, but the backswing causes the right leg to push into the ground, and that as what causes the body to start to move to the left.
This is the first time you actually generate power through the back leg with your back leg. All elite runners generate speed here. The motion that makes you move forward is the bending of the spine. Practice one side at a time, then alternating. When you think you have the hang of it, move on to the cross pattern slide, which is the walking/running pattern.
Cross Pattern Slide
It is hard enough to use the correct back muscles during the slide, and is more difficult during the cross pattern. One of the few major running glitches is when, for example, the right leg moves forward, the back muscles on the right hike the leg up instead of the low back muscles on the left propel you forward. If it is too hard, go back to the slide a few times, then try the cross pattern again.