Enhancing tolerance to cold exposure--how successful have we been?

The risk of accidental hypothermia is always present in persons living at high latitudes, with cold water immersion representing the most extreme challenge. While most of the effort concerned with protection against cold exposure has involved finding ways of decreasing heat loss by improving insulation some attempts have been made in finding ways of improving cold tolerance by modifying the thermoregulatory response to cold. The main strategies that have been used are: - thermal acclimation, physical exercise, dietary enhancement of thermogenesis, pharmacological enhancement of thermogenesis and manipulation of thermoregulatory set-point. This paper briefly reviews the success of these strategies. While none of the strategies examined have resulted in concrete methods which are routinely used to improve cold tolerance, it is concluded that the pharmacological enhancement of cold thermogenesis using ephedrine in combination with methylxanthine represents the most promising method for delaying the onset of hypothermia in humans.