Thermogenetic mechanisms involved in Man's fitness to resist cold exposure

People whose evolution has taken place in contrasting climates, appear to have an almost identical critical temperature (27–29°C). This does not exclude the existence of minor variations within and between populations with regard to individual fitness to resist cold exposure. The main factor by which Man's fitness to resist cold exposure can be varied, appears to be thermogenesis. The biological variation of BMR, shivering, a possible non-shivering thermogenesis, and the maximal aerobic power is reviewed. BMR of an individual can vary with diet, general health, habitual physical activity, as well as various environmental conditions, conceivably including cold exposure. A definite inter- and intra-individual variation in shivering threshold exists. The underlying mechanism of these differences is poorly understood, however. Firm evidence in favour of a non-shivering thermogenesis in Man is lacking. Man's capability to raise his metabolism in muscular exercise is an important part of his fitness to resist cold exposure. This capability can be assessed by measurement of maximal oxygen uptake. Maximal oxygen uptake is influenced by age, sex, health, diet and habitual physical activity. It is questionable if evolution in contrasting climates brings about variation in maximal oxygen uptake.