FYI: Biofeedback isn't your body adapting to new environments. Biofeedback is learning to gain volitional control over certain aspects of your autonomic nervous system (the part of the nervous system that usually functions automatically, i.e. blood vessel dilation, heart rate, digestion, etc). There are different techniques and technologies that help people learn to do this. It's used medically for lots of different things. Of interest to climbers would probably be that people have learned to dilate and/or constrict blood vessels in their extremeties, warming up surface temps. of one hand 5-10 degrees while the other stays a normal temperature, all w/out muscle contraction. But before all you alpine climbers get too excited, I think there are some limitations, one being that it requires being calm, meditative and relaxed...which is hard to do when you're gripped on a climb. Might be useful at a bivi though? If you're interested, I think it's technically considered part of psychophysiology.