In my Dojo the Yori Ashi comes up nearly every night. Last night we stood in a fighting stance just back from the padded wall and shifted to the wall and delivered reverse punches, jabs, front kicks and hammer fists. The strikes were observed by our Sensei, but it was the body shift that was the focus of his instruction.
Body shifting, simply put, is moving the seika tanden from Point A to Point B. As in all methods of generating power, body shifting can be used offensively and defensively. Yori ashi is produced by extending one foot to a wider or longer position, then retracting the other foot to re-establish relative length or width. Sensei Bob Remington
The part of the quote above from Sensei Bob Remington that we often work on in my Dojo is using body shifting offensively. It is emphasized that when shifting, you lead with the Hara and the body moves as a unit – fast and solid.
The emphasis is here: we don’t shift, then strike. The Yori Ashi works best with the shift becomes the strike. Envisioning your target behind the opponent, drive the body forward, and let the controlled momentum of your entire weight (plus your explosion into the technique) be the weapon.
Liken it to this: Getting hit with a baseball, or getting hit with a baseball that is duct-taped to the front of an oncoming truck.
That impact, my friend, is real Karate.