I watched a Discovery Channel (I think) program a while back where a guy was working bare handed in sub freezing temps doing some kind of work that required finger dexterity. They heated his chest and it kept the blood vessels open to his hands. He was able to perform without so much as even feeling uncomfortable. They then removed the heat and he froze up (not literally) in very short order....just like you would expect.

I never put the two together before watching that program, but I remember vividly putting a hand warmer in my shirt pocket. I felt quite hot but not so much so I was compelled to remove it. The day was raining sleet and my hands were literally steaming and I wasn't the least bit cold. I thought at the time that I just had good blood circulation, but now I think it was due to that shirt pocket hand warmer.

With the weather going the way it is, I'm going to try it again. I hate when I can't feel my spool because my thumb and finger tips are iced up. (Ah, the trials of fishing... )