Countering Heat Stress
Measures to prevent and reduce symptoms of heat stress naturally relate to causal factors and physiology. Top on lists of medical and governmental prescriptions to combat risks of heat stress is to drink plenty of water to replace fluid lost through sweating. The amount of water needed is a function of weather, workload, and personal physical attributes.Countering Heat Stress
The slower the wind and the greater the temperature, humidity, and direct sunlight, the more water a body needs. While wind reduces the risk of heat illness by increasing the rate of sweat evaporation, the effect of full sun can be equivalent to a 13 degree increase in air temperature. Since the body generates more heat during heavy work than during light or moderate work, the amount of water needed also rises with the strenuousness of the task performed. Finally, personal attributes also affect the amount of water they need. Persons who are younger, better rested, more physically fit, and acclimatized to work in hot temperatures are less likely than others to suffer heat illness, given similar work conditions.
Mainly because thirst does not provide a timely or precise signal of the body's need for water, most workers exposed to hot conditions do not sufficiently match their fluid consumption to sweat loss. Thirst typically is not perceived until an individual reaches a water deficit of about 2 percent of body weight. Clear in the exercise physiology literature is that "ad libitum water intake" results in incomplete water replacement or voluntary dehydration during exercise and/or heat exposure. So instead of depending on thirst to signal when and how much to drink, a worker should drink 5 to 7 ounces of fluids every 15 to 20 minutes to replenish necessary fluids in the body. Military guidelines recommend drinking up to one quart per hour under the hotest, most active conditions, plus resting for many minutes of each hour. For moderate work in temperatures of 82-90 degrees, the military guideline is about 200 ounces of water during 8 hours, and only 10-30 minutes of rest per hour.
