The components of the body including the muscles, the bones, the fascia.
Well, someone just p.m.'ed me that it is "energy" that is spiralling. In the technical sense, it cannot be actual energy (where does it originate from, where does it get power from, how does it work that you can control "energy", etc.). In the idiomatic sense, energy boils down to certain feelings, mostly subjective. Maybe the sorts of things that someone is imagining, as opposed to something that is tangibly happening. Regardless, it's always a positive thing to question "what's really going on here?".
As an aside, I've had a number of discussions in which people indicate someone can do something, but they can't really explain it in terms of western-science terminology. Great.... but imagine how much more you could do if you actually knew exactly what was happening and you could describe it.
I watched some videos of one well-known teacher doing some interesting demonstrations while completely failing to describe what he was actually doing (his English wasn't so good, but still good enough). Watching the demonstrations I had the impression that the teacher was shown how to do some of these things, but hadn't quite thought through everything that was happening. If he had, he would have been able to spot some further things to do *plus* he could have taught his students how to do these basic kokyu things. It's imperative to analyse and investigate, to talk (think) out loud with like-minded fellows.
In terms of muscle, bones, and fascia being what is 'spiralling', I'll quote something Chen Xiaowang said to me about another but related topic: "If it was that simple, why would experts make such a big deal out of it?".