Memories that live in the body

It is somewhat miraculous, that shaping your body in different ways has the ability to awaken feelings, memories and thoughts trapped beneath the skin, perhaps deep inside muscle tissue. Is it the same with pain? Do certain movements evoke negative synaptic connections while other stir up relaxation?
Well, I rediscovered these sensations two weeks ago during a class focused on flow taught by Grayson Sensei. Instead of beginning with the traditional first technique, tenkan (I should eventually learn how to spell this), we were instructed to try to feel the connection between ourselves and our partner. To focus our attention, our nerves, or feeling the warmth and energy passing between us. The truly incredible thing was although they seemed to be standing still, they were moving! They were impossible to grab! Their arm was in multiple places at once, it felt much like how Herman Hesse's Siddhartha described his river of enlightenment: always within the same river body, yet constantly changing and refreshing.
What were we really doing with this exercise? Allowing energy to flow out of our bodies while receiving another's energy flow. Ki.
What exactly is energy? Why can I sometimes feel it course through my body, making my skin warm? Then again, most of the time I am completely unaware of it. If we are comprised of atoms and atoms are comprised of constantly orbiting particles that have energy- does that mean that on an atomic level we are never truly still? Is it truly a Saotome Sensei describes, that we are reverberations of the big bang, products of eons of evolution, complex packages of highly condensed and specialized matter (and yet still mostly empty space!)? It is more than my mind can contain at this late hour.
Upon feeling the presence of energy in my body, I was reminded of the first time I ever actually noticed its existence-- lying on a table with needles rising from my palms, face, elbows, knees. The first time I received acupuncture it seemed as if little quivers of energy shook just below the surface of my skin; but rapidly this accelerated into vibrations that coursed along my meridians. I was a bit scared, yet mostly awed that such a presence resided within me and I had been completely unconscious of it. When the needles were removed I remember feeling alert yet relaxed at the same time . . .