I'm always finding new Aikido avenues to explore. Lately I've been experimenting with the idea that Ki extension must be accompanied by a relaxed body in order to be effective. The first time I had an inkling that this may not be quite the case was during a demonstration of weight underside. The exercise has 2 ukes, one on each side of nage, grasp nage's forearms and, together, try to lift nage off the floor. I usually demonstrate this exercise two ways. First with my arms held stiffly at my sides with elbows locked. My partners are able to lift me in that position. The second iteration I relax my body, especially my arms and shoulders, and as they lift I let their force circle around, without stopping at my shoulders, and feed it back to them in the form of downward pressure. My feet stay firmly planted on the mat.
As I have continued to practice this exercise I am noticing that it's getting more difficult for them to lift me even while I remain in the stiff armed position. After checking and confirming that I hadn't added 20 or 30 pounds of stealth weight I surmised that something else must be afoot.
I then began to practice the exercise totally stiff and found that I could indeed remain rooted to the mat with ease. To make things more difficult for myself I had my partners drop their centers below mine so they could lift from underneath my center of gravity using their legs and not their back muscles. Same result. In fact the downward force I feel is more evident and active from the stiff armed position. When they try to lift me my partners are literally driven to the mat by the force of their own energy.
I'm now experimenting with katate tori. I have my partner grab my wrist and push into my shoulder. I'm noticing that I can remain immovable regardless of my physical state, be it relaxed or stiff armed. I'll continue to explore this aspect of Ki development and application and most likely will have more to post about it in the future.