Simple and multiple regression analyses were used to assess the influence of 12 white men's fitness (aerobic capacity 44-58 ml O2.min-1.kg fat-free mass-1), fatness (mean skin-fold thickness 5-20 mm, body fat content 15-36%), and age (26-52 yr) on their thermal, metabolic, cardiovascular, and subjective responses to 2 h of whole body cooling, nude, in air at 10 degrees C. Fitter men had slower heart rates, and fatter men had higher blood pressures. Fitness had no effect (P greater than 0.39) on any measured response to cold. Fatness was associated (P less than 0.01) with reduced heat loss, heat production, and mean skin temperature; unchanged heat debt; and increased tissue insulation. Age had the opposite effects. When the confounding effects of fatness were held constant by multiple regression, older men responded to cold as though they were 1 mm of skinfold thickness leaner for each 3-4 yr of age. We conclude that aging, even between the relatively youthful ages of 26 and 52 yr, is accompanied by a progressive weakening of the vasoconstrictor response to cold.
The purpose of this paper is to summarise and discuss the changes in glaciers, king penguins and fur seals reported by the nine wintering parties and 11 summer expeditions that have visited Heard Island since 1947, with emphasis upon those of the years between 1947 and 1971. These early years were notable for an initial period (1947-55) of minimal change, and a subsequent period(1963-71) of rapid change in which a complex pattern of asynchronous glacier retreat and readvance was observed and the main features of the island's recolonisation by king penguins and fur seals were established. Subsequent expeditions have reported continuing glacier recession, evidently in response to warmer air temperatures, and a continuing exponential increase in king penguins and fur seals. The glacier observations show that the Heard Island glaciers are sensitive indicators of climate change in the Southern Ocean, and of the interactions between climate and glacier topography. The island's recolonisation by king penguins and fur seals is attributed mainly to an improved food supply which may itself, like the glacier recession, be a response to changes in atmospheric and oceanic circulation. Glacier recession and its consequences are changing the island's coastline, and the expanding populations of king penguins and fur seals are damaging the vegetation. All these phenomena, occurring as they do in an island with a hitherto undamaged ecosystem and no introduced predators, clearly warrant continuing study.
Firefighters' thermal environment was continuously measured while they attempted to suppress well-developed experimental bushfires of intensities commonly faced by hand-tool crews, and also while they built fireline in the same way without fire, during three summers in Australian eucalypt forests. They worked far enough from the flames to avoid painful intensities of radiant heat (>2 kW m-2) on bare skin and usually experienced 1.6 kW m-2 - little more than the intensity of sunlight Fire had negligible effects on average air temperature, humidity, or wired speed. Exertion accounted for 71% of the total heat load, fire and weather for the remainder. Evaporation was effectively the sole means of heat dissipation, and predicted sweat loss exceeded one litre per hour. Indices of heat stress usually exceeded occupational limits proposed for heat-acclimatized men, although little additional strain resulted. We conclude that firefighters should be fit and acclimatized, wear light and loose clothing that imposes minimal resistance to evaporation, and drink at least 1 litre of water per hour.
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