My partner places her hands on my shoulders while facing me. The heels of her hands lie just below my collar bones, her fingers rest lightly on the tops of my shoulders. We begin by having her lightly push allowing me to stabilize my center and become acquainted with the general intensity and direction of her applied force. For her part, in addition to providing the force of her push, she will be learning to recognize when I have centered; it's easily felt. When she can feel my center she will apply more force to her push.
At this point the exercise diverges from the simple static Ki exercise from which it was derived. What I want to do is divide the force of her push in such a way as to make one side of her work against the other. I do this by creating a "positive" point for her to push against on one side and a "negative" point for her to fall into on the other. As a result, her arm pushing against my positive point will cause her shoulder to pop up while her opposite side arm will extend into what feels like a void even though she remains in contact with me continuously. As she corrects her compromised structure I will reverse the direction of my positive and negative points causing further disruption of her posture and balance. As I practice this exercise I can see how the shortening of her arm that pushes against my positive point causes her other arm to lengthen. This makes it difficult for her to apply any kind of effective force at my shoulders. (Note for uke, it's important to apply pressure continuously during this exercise.) With continued practice I will develop the ability to capture her push on contact and compromise her posture and balance from the outset.
I can vary the exercise by allowing myself to be pushed backwards. While moving I can experiment with creating positive and negative points in order to change direction on my terms or simply stop in order to allow myself to be statically tested. I can also have uke push my shoulders from behind or push at my hips from front or back.