This stuff, and other internal body skills, have escaped empirical explanation throughout history, for a reason (we just don't know the reason
For example, westerners have been trying to figure out how tum-mo, the meditative practice through which Tibetan monks raise their body temperatures in order to dry cold, wet sheets draped over their bodies, works for almost a century. During that time, Harvard and other western researchers have scientifically analyzed groups of monks for the past 30 years. When the Harvard team initially published its findings in 1982, they hypothesized that the monks' ability to raise body temperature by as much as 17 degrees F was due to "vasodilation", and "[t]he physiological changes are . . . a by-product of religious practice". In 2002, the lead researcher, Herbert Benson, who had continued to try to arrive at a scientific explanation for the phenomenon, told the Harvard Gazette
, "[t]he heat they [the monks] generate during the process is just a by-product of g Tum-mo meditation" -- so really no additional concrete revelations since the original findings. Again, these guys and gals aren't from the local JC.
Now, who knows whether or not the meditative / intent-driven processes, and the resulting physiological changes, by which the human body can be altered to produce aiki are more or less complex than those needed to voluntarily raise body temperature. All I know is, if multiple teams of dedicated researchers on different continents have spent three decades and millions of dollars trying to figure out the former, we're not gonna figure out the latter in this thread.
For me at this point, yes: "like a bag of hammers"
more often than not.