Army Personnel Research Establishment Ministry of Defence

In comparison to exercise in cold water, the development of hypothennia during exercise in cold air is relatively unlikely. However, Pugh (1) described incidents of accidental hypothermia in hill walkers and climbers, and noted that most cases occurred at temperatures near freezing point and in the presence of wind and rain. Pugh (1) also identified fatigue as a factor influencing the onset of hypothermia. Simulating a cold/wet/windy environment in the laboratory (+5°C dry bulb ambient temperature [TAmb] and a 4.2 m·s-1 air current), Pugh (2) produced a cold stress that induced a 1°C decrease in rectal temperature (Tre) and a 50 % increase in oxygen consumption (V02) during low intensity cycle exercise (67 watts or-30 % maximum oxygen consumption [V02 maxl) compared with a cold/dry/no wind control condition. These differences were attenuated at 100 watts and abolished at 150 watts (-50-60 % V02 max). Although only based on three subjects, these fmdings had important implications for the conduct of recreational and job related activities in cold environments. More recently, Hampton and Knibbs (3) extended Pugh's experiments to a larger sample size and observed a fall in Tre but no increase in heat production during cycle exercise at 55 % V02 max in a cold/wet/windy environment compared with a cold/dry/windy control condition. The aim of the present investigation was to establish a suitable laboratory model to investigate the physiological responses to prolonged walking exercise during cold exposure in man. This mode of exercise was deemed the most applicable to the study of human metabolis