Posting a reference to Tim Noakes yesterday reminded me of his recent work with Lewis Gordon Pugh, a British 'Environmentalist, Explorer and Swimmer.'
Pugh is most famous for his cold water swims which he usually does to publicize global warming and the melting ice-caps. These swims are done without a wetsuit, in water as cold as zero degrees centigrade (because of the salt seawater freezes a couple of degrees below zero).
An article in New Scientist magazine a few months ago reveals some of the science behind Pugh's remarkable ability. Most interesting was the discovery by his trainer, the aforementioned Tim Noakes, that Pugh is able to consciously raise his body temperature.
As the swim gets closer, he psychs himself up by listening to music by the likes of Eminem and P. Diddy. In the minutes before entering the water, Pugh recalls these emotions and is able to raise his core temperature, without doing any physical exercise, to 38.4 °C. That's an extraordinary 1.4 °C above his normal body temperature. Such "anticipatory thermogenesis" has been observed before, but not to such a high degree.
You can read the actual paper in the appropriately named 'Journal of Thermal Biology': Body temperatures during three long-distance polar swims in water of 0–3 °C.
Pugh appears to have reached some of the limits of the human body:
In 2007 he swam 1 kilometre in the coldest water yet - a glacial -1.7 °C - at the geographic North Pole.
"When I went below 0 °C the cells in my fingers started to freeze. It took another four months before I could feel my hands again," he says. After reaching his goal of swimming both in the Arctic and in Antarctica, Pugh has for now hung up his towel.