The negative effects of heat stress on human performance, athletes, military personnel and fire fighters, are well documented facts. Private research and government tests have consistently proven that an ambient temperature exceeding a person’s normal skin temperature (90-95°F at the surface) causes mental fatigue and physical exhaustion to begin. The higher the temperature and the longer the duration only makes it worse. The reason is simple. The skin is our body’s primary cooling system. In fact, 65% of the heat generated by our bodies exhausts, or radiates, out our skin. Another 25% evaporates through sweat glands in our skin. However, this remarkably efficient cooling system is also a double-edged sword; just as much as the skin helps us keep cool, it is nearly defenseless against external heat sources greater than our own body temperature. Just as much as our body releases heat, it also allows heat in. Thus, any environmental condition or circumstance that tips the natural balance between a warm body and a cooler surrounding will quickly and dramatically stress a body’s ability to function at peak performance.
NASA conducted a study that states when the temperature around you is 95 degrees for an extended period, people can make 60 mistakes per hour and they don’t even realize it. When you perspire, almost half of your blood moves to the skin to produce moisture in the form of perspiration to naturally cool the body. The heart is pumping up to 150 beats per minute with less volume to get the blood to the skin. That means the rest of your organs, including the brain and your muscles, are only operating on half the blood they normally need. This interferes with cognitive thinking skills and can provoke emotions like anger even combative behavior.
Heat stress can be caused by environment, but also by activity and clothing. Heavy outdoor work, aggressive sport activities, extreme working conditions like firefighting, heavy industrial work, military training, and any activity involving protective clothing or heavy gear can cause heat stress. Any environment or circumstance that blocks the body’s natural ability to release internal heat energy will cause heat stress. And vise versa, any environment or circumstance that exposes body to heat sources higher than 90-95°F will quickly overwhelm a person physically and mentally. It can happen at low temperatures over time or instantly under extreme conditions. Imagine the comparison of lying in the sun on a 90°F day verses stepping into a sauna at 150°F. Eventually both will leave you exhausted.
In conclusion, mental errors by workers in ambient temperatures above 95°F are caused by the inability of the body to release internal heat energy and the eventual over heating and dehydration of the body. These two factors are responsible for a cascading series of events that cause a person to be both physically uncomfortable and feeling fatigued along with diminished thinking skills (although they might not realize it). Other effects of heat stress may include negative emotions like sadness or anger and the potential for combative behavior. All of these things are caused simply by the body’s inability to cool itself when the ambient temperature exceeds 95°F.
Co-written by Scott Gammons and Rich Shafer. Scott Gammons is the Vice President of Adroit Medical Systems, Inc. Rich Shafer is the President of Shafer Enterprises, LLC / Cool Shirt.net. Both companies develop and manufacture thermoregulation and temperature therapy products for medical, military and sport activities.
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