Okay. I've heard from more than a few of you about the "reach back" technique and I think there needs to be some clarity.
The "reaching" part is, in fact, a twist of the torso and a trick of the eye. Do not, in fact, "reach" back. If you look at the videos, the arm is not extended back, it "falls" back as the body twists at the waist. It appears to reach, but it does not. Then, as the body twists back around to the front, it "pulls" the arm forward. (do not jerk your arm, just let it accelerate naturally. It's hard to diagram this without showing you, but please, do not REACH. Just let your body twist.
I hope that helps.