While recently ill, not doing a whole lot, and bored I wondered: if through meditation you can feel heat and increase the temperature in your hands, can you also lower it? To what degree can you do so?
Initially, I found I could sort of increase the temperature a little, but not reliably, and wasn't able to lower it.
Armed with an IR thermometer, and in sadomasochistic zen disciple style (or what I'd assume to be that), 120 degree hot water on tap and 30 degree icewater in a bowl next to it, I got a lot of temperature shock as I moved my hand from one extreme to other.
Well, after a fair amount of that, focusing and being mindful of all the perceptions involved... the feeling of cold, pain, hardness, inflexibility, whiteness, etc in the icewater, and the feeling of heat, pain, fluidity and flexibility, redness, throbbing, the pulsation of the palm, the sensation of several points (such as in the webbing between the thumb and index of finger) of especially increased sensation and throbbing.
Next, I repeated my earlier attempts. After a little practice, and focusing on the memories of the extremes, including standing where I was and going through the motions with a tap that wasn't running and an empty bowl, I certainly became more adept.
Ignoring my left hand, I raised the temperature of the right such that pressing both hands to my forehead, the left one felt cold, and the right, hot. And I could now induce cold. All in all, I could raise the skin temperature to about 98 degree, and decrease it to 76 or so. Yeah, hardly impressive compared to the 112 deg or whatever Tibetan monks get but hey, it takes practice grasshopper.
It usually takes a couple of minutes of focus at least, and is more difficult outside a quiet/relaxed environment. I can also raise the temperature in one hand, and lower it in the other.
I find that "cold" is harder to do than "warm", but after I do it, the results tend to stay around longer. I seem to reach a maximum threshold for "warm" that seems a bit low to me.
Warmth is pretty easy, because you can just do the typical meditative muscle-scan-tension-release and get a fair amount through that. I think that gets you a somewhat "normal" vasorelaxed state. But pushing it higher is difficult, and thing I've learned to focus on only adds so much by itself.
Cold is harder because there isn't much to focus on. I tend to use memory/visualization and try to focus on the feeling of hardness in the skin if anything. Once I get it started though, I manage to make my hand fairly chilly. I suspect you can go quite a bit further, like the blue fingers of Raynaud's. Might be a neat parlor trick or to shock your GF with but the warmth thing has a lot more practical benefits-- the circulation is necessary and your dexterity/endurance increase as the temperature does.
But there's also something interesting about it. In understanding the differences in perception and how to induce either state, I'm a lot better than I was in the past at increasing my hand temperature. I can finally do it with 100% consistency (of getting SOME increase) and the effects are more powerful than when I practiced inducing warmth alone in the past.
btw-- anyone know at what skin temp the Raynaud's blue skin thing happens?
