The January 2014 Arctic Frontiers Conference saw Professor Hannu Rintamäki of Finland’s University of Oulu and the Finnish Institute of Occupational Health give a presentation on work and well-being in frigid temperatures.
But humans evolved as tropical animals and our thermal comfort zones are still controlled by that history. “Humans come from the tropics,” the Finnish professor reminds us, which explains why we do what we can to maintain a tropical microclimate in our dwellings, at work, in cars and beneath our clothes when outdoors.
- To be comfortable in water, we require a water temperature of 33° C.
- Our optimal air temperature on land when at rest is 27° C.
- The safest day temperature for people in the Mediterranean Region is 24° C, whereas the safest day temperature for Finns is 14° C.
- The safe limit for working in the cold is -10° C, while to avoid hypothermia when sitting still without clothes for one hour, the temperature should not be lower than -1° C.
- We feel best when our core body temperatures are in the range of 36.5° C to 37.1°C when we are not in motion.
- We feel best when the average temperature of our skin is from 32.5° to 35°C and when the difference between local body part skin temperatures differs by no more than 5°C.
- While the ideal (skin temperature) is 33°C, we begin to feel discomfort when temperatures climb over 35° or are under 31°C
- our performance starts to decrease when skin temperatures drop below 30° or rise above 35°.
- health is at risk when the surface temperatures of our bodies dip below 15°C or rise beyond 45°C.
….. “But low skin temperatures are not the only stress factor. Continual changes in temperature are also troublesome,” says Rintamäki.
“As skin and the tissue below is cooled down, muscle power decreases by two percent per degree,” says Rintamäki. Arms and legs get cold most rapidly, and thin fingers are less capable than thick fingers at tackling the cold.
….. Not all cold is bothersome. Some types of cold increase well-being and comfort. A modest exposure will help you become more alert. A short exposure to extreme cold, such as ice-bathing, is an example.
The shock of icy water triggers the production of hormones such as endorphins and cortisol (hydrocortisone), and these make you relax afterwards.