Thirst and work capacity of older people in a hot environment.

In a hot environment, especially during exercise, the main role of thermoregulative mechanisms is to dissipate excessive heat from the body. The most effective way of heat dissipation is sweat production and its evaporation off skin surface. Intense sweating results in a considerable loss of water and electrolytes. There are some results that indicate lower thirst of older men than young ones in response to a hot environment and osmotic stimuli. Our studies conducted in men of different ages exposed to a hot environment indicated that there were no significant differences in rectal temperature (Tre) or heat storage (S) among groups at rest. Lower Tre and lower S in older men with higher physical capacity for their age than in young ones with average physical capacity was shown. However, in all the experiments significantly lower thirst in older men than in the young was indicated. Special attention should be paid to fluid replacement among workers in a hot environment because of lower thirst and lower hydration of older men. These individuals may be exposed to dehydration risk during prolonged exercise, despite the possibility to tolerate heat strain as well as young ones. Further studies are necessary because of some diversity in the meaning of the results.