In very simple terms, heat injury takes place when the body produces so much heat that the core temperature of the body rises above its normal level of 37 degrees Centigrade (98.4 degrees Fahrenheit).
Serious damage to the body's organs does not really start taking place until the core temperature rises to about 40 degrees. Once it exceeds this threshold, overheating can result to damage to vital organs including the brain. In fact temperatures above 45.6 degrees centigrade (114 degrees fahrenheit) are incompatible with life
How the Human Body Generates Heat
The human body in effect is a machine, and when it performs work (such as moving joints and muscles) it generates heat. The more physical work one does and the harder one works, the more heat is generated.
If this heat were to remain within the body it would cause the body's temperature to rise – but fortunately, nature has evolved an effective way of getting rid of this heat. Wherever heat is produced, the blood that flows round the body acts (in a manner analogous to the coolant in a motor vehicle) to carry the heat away from the region generating heat. This warmed blood carries the heat to the surface, where it is given up to the surrounding atmosphere through the skin.
Heat Loss by Conduction, Convection and Radiation
This type of heat loss – where heat from the hot surface of the body is lost to the cooler air outside the body – takes place more easily the larger the temperature difference between skin and outside air. For example, if body temperature is 38 degrees and outside temperature is 27 degrees, heat loss is much more effective than if the outside temperature is 36 degrees. If, on the other hand, a man is working in a place where the outside temperature is higher than 37 degrees, this type of heat loss cannot take place. He will actually take in heat from the surrounding air.
Heat Loss Through Evaporation of Sweat
In addition to heat loss by conduction convection and radiation, the body also loses heat through the evaporation of sweat. A hot body sweats – and the liquid that perspires onto our skin evaporates, drawing heat from the surface of the skin during the process.
This cooling process through evaporation is one of the most effective ways of cooling the body. For sweating to take place, however, the body must be well hydrated – in other words, the body must have a good supply of fluid inside it to make sweat.
Importance of Hydration to Prevent heat Injury
This is why it is important to make sure, if you are working in a hot environment, to drink plenty of fluids. Just drinking plain water is not enough, because the sweat lost from the body contains both water and electrolytes (salts). To replace the lost electrolytes, one should drink water containing dissolved salt. This can be in the form of commercial sports drinks or simply by adding a small amount of salt into your drinking water. Another practical method is to eat salty foods in addition to drinking plenty of water.
A good way of ensuring that you are well hydrated is to make sure that you pass clear urine at least twice a day. If the urine you pass is reduced in quantity or dark in colour, it shows that the urine is too concentrated – and indicates that you are dehydrated.
Factors that Can Place a Man at risk of heat Injury.
Men who are not physically fit or are overweight are more likely to develop heat injury. It is important, if you have to work in a hot environment to which you are not accustomed, that you acclimatize yourself by spending at least a week getting used to the atmosphere and that you start with light work for short periods until the body gets used to the environment before commencing work at your usual tempo.
Heat Injury is a major risk for men working in hot climates for the first time – particularly those like military personnel who have to perform heavy duty in hot environments. In the US Army over the past 20 years, the incidence of heat stroke has increased seven-fold. In 2008 alone, there were 299 hospitalizations for heat stroke and 1,467 hospitalizations for heat injury or exhaustion in the US Army.
Sanjiva Wijesinha - Dr. Sanjiva Wijesinha, Associate Professor at Monash University medical school, writes on health, travel and medical topics.
