The Effects of Extreme Heat

In medium to extreme heat, the body cools itself by perspiring or sweating. Sweat releases a lot more than just water from the body – it also releases a number of minerals (or electrolytes) such as magnesium, potassium, calcium and sodium. These electrolytes are essential for the body to maintain strong , healthy muscles, high concentration and energy levels.

Water makes up 70% of our muscles and about 75% of our brain. So it’s not surprising that as minerals and water become depleted, muscles aches and cramps, fatigue and thinking can be affected. Research shows that dehydration can diminish thought processes and memory, therefore adversely affecting quality of life. This should not be surprising considering that an imbalance in just one mineral can actually lead to substantial biochemical imbalances, so maintain and replacing the full array of minerals and trace minerals in the daily diet is important, particularly during times of heat stress.

It’s proven that water alone cannot sufficiently replace lost electrolytes. Pure water is absorbed slowly and cannot be retained by the body. During the first minute of consumption, the body absorbs HydraSafe® significantly faster that it would water.

Clinically – four dominant heat disorders are commonly described:

Whilst these four disorders are commonly known, it is not unusual for the criteria distinguishing them to be inconsistent.

Heat Cramps

Heat cramps are painful, involuntary contractions of the muscles associated with working in hot conditions. Heat cramps are most usually experienced in individuals who are dehydrated – in particular where electrolytes are imbalanced due to sweat and fluid deficits. As sweat losses are greater in the heat, susceptible individuals would logically be at increased risk of cramping when working or exercising in climates / conditions with high to extreme temperature and humidity.

Heat Syncope and Heat Exhaustion

Heat syncope (fainting) and heat exhaustion result from the inability of the body to control both its own core temperature and its circulatory demands.
Fainting occurs when there is reduced blood in the veins returning to the heart as a result of excessive pooling in the blood vessels on the periphery of the heart which compromises the effectiveness of the heart, making it impossible for an individual to maintain blood pressure.

Heat exhaustion results from severe fluid and salt loss and may manifest with elevated core body temperature and signs of cerebral ischaemic (ie. a lack of blood to the front of the brain). An individual can also display symptoms of considerable stress response and impaired tissue perfusion.

Heat Stroke

Heat stroke is a severe condition resulting from breakdown of the body’s ability to control both its own core temperature and its circulatory demands, resulting in a severe (ie greater than 40C) or prolonged rise in body temperature and consequent tissue injury.
Organ damage is widespread and results from both inadequate oxygen in the body tissue and a very high fever.
Acute injury to the heart, kidneys and liver may be permanent and approximately 40% of heat stroke cases could result in fatality.

Risk factors for heat illness

The risk of all forms of heat illness is greatly exacerbated by poor hydration. When temperatures are high to extreme, and combined with high humidity, fluid losses in sweat may exceed 1 litre per hour which exposes the individual to progressive dehydration during prolonged work in the heat.

Clearly, adequate hydration is a critical factor in prevention of heat illness, as is acclimatisation, which enhances the body’s ability to regulate core temperature and circulatory functions. In many situations, an individual can self-pace to adjust either the work rate or the duration of work intervals to maintain thermal balance. The danger is that when the work is externally paced (eg by machinery, quotas, peer pressure etc), or the sustainable level of work is perceived as being unacceptably low, individuals will push themselves beyond the safe limited and be at risk of developing heat illness.

At most risk - are those who are poorly hydrated, un-acclimatised, overweight or physically unfit.

Physiological effects of dehydration

As dehydration increases, there is a gradual reduction in physical and mental performance. There is an increase in heart rate and body temperature, and an increased perception of how hard the work/exercise feels, especially when exercising/working in the heat.

Dehydration of greater than 2% loss of body weight increases the risk of nausea, vomiting, diarrhoea, and other gastro-intestinal problems during exercise.
Dehydration reduces the rate of fluid absorption from the intestines, making it more difficult to reverse the fluid deficit. You may end up feeling bloated and sick if you delay fluid replacement.

Of all the physiological causes of trouble that can cause early fatigue during work/exercise, dehydration is arguably the most important, if only because the consequences are potentially life threatening.
(Source: Sports Dieticians Australia)

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