The Thermal Environment

Myth busting in heat stress.

• By Ross Di Corleto
• 04/02/2017
• 2 Comments

There are many theories discussed in heat stress, some are based on fact but others are not.

They often result in debate and varied opinion. Here we review five often recited statements.

1.  Drinks containing caffeine are always bad for you in the heat.

This is actually a myth but with qualification.

There have been a number of recent studies that suggest this may not always be the circumstance when working or exercising.  In these studies, moderate chronic caffeine intake did not alter fluid-electrolyte (salts) factors during exercise or negatively impact on the ability to perform exercise in the heat. They did in fact add to the overall fluid uptake of the individual.

It is important not to forget that excessive caffeine intake can result in nervousness, insomnia, gastrointestinal upset, tremors and tachycardia in some individuals.

For a bit more info on this check out a previous blog at http://www.thethermalenvironment.com/what-is-the-impact-of-caffeine-in-relation-to-heat-stress/

2.  Changing from short to long sleeves does significantly increase your risk of heat stress.

This is actually a myth but note the word “significantly”

Increasing the length of clothing can have a negative impact by decreasing the area of skin available to evaporate sweat and hence cool the body. However, given the surface area in question, the impact is generally not high in relation to heat stress and very dependent on the environment. Having said that, there may be a larger impact on thermal comfort. The decision to go to long sleeves needs to be weighed up against other risks associated with the scenario such as cuts, abrasions, burns and skin cancer and the thermal comfort of the individual.

More detail on this one at: http://www.thethermalenvironment.com/do-long-sleeve-shirts-increase-the-risk-of-heat-stress-for-outdoor-workers/

3.  There are no long-term impacts of heat.

This one is definitely a myth.

There is evidence on the increased incidence of kidney stones related to occupations in hot environments such as steel & glass, which are pretty convincing. Also, a study which looked at heat waves in Adelaide (Hansen et al 2008) picked up an increase in hospital admission rates for kidney complaints for men between 35 to 64 years old. More recently there are increasing concerns relating to the rising incidence of kidney disease in South American agricultural workers (Jimenez et al 2014).

Other studies have suggested that long term heat exposure can impact on the liver, heart, digestive system, skin conditions and the central nervous system.

Check out an earlier blog at: http://www.thethermalenvironment.com/chronic-illness-associated-with-heat-stress/

4.  Alcohol is not good for you in the heat.

Yes, this one is a fact.

One of the key aspects of the issue is the diuretic effect of alcohol, i.e. its ability to make you pass more fluid than you drink. It is generally accepted that alcohol can cause you to lose an additional 50% of fluid, i.e. you drink 100mls but pass approximately 150mls. Hence, as you drink alcohol your fluid levels can actually go backwards. Alcoholic drinks are not a recommended method for rehydration as they will dehydrate you faster. Stick to non-alcoholic drinks or water for that purpose. If you must drink, drink responsibly and follow a few basic rules.

• Make sure you are well hydrated before you head off to an event where you may have a few alcoholic drinks.
• As you drink also top up with water in between to help keep the fluid levels up.
• Before you go to bed have another glass of water (sports drinks can be good here to replace some electrolytes you have lost during the visits to the bathroom).

A bit more detail at: http://www.thethermalenvironment.com/heat-stress-and-alcohol-not-a-good-combination/

5.  Drinking too much water can kill you.

This is also a fact but again with qualification.

The condition known as hyponatraemia requires a significant intake of fluid to occur and there have been situations where this has been overdone. Two recent examples from the US included:

• a college football player who was given 5 litres of intravenous fluids while ingesting 3 additional litres of hypotonic fluid (a sports beverage) within 5 hours, and
• a high-school football player who died in 2015 after reportedly drinking 16 L of fluid during practice to alleviate muscle cramps (Rosner 2015).

The condition was also noted in participants in the Kokoda trail in New Guinea by Rothwell et al in a 2011 study.

Hyponatraemia is a serious condition that can result from an excessive intake of fluid often in sporting and endurance scenarios. However, it is unusual and has a much lower likelihood of occurring in hot scenarios than the risk of dehydration. So maintain fluid intake but don’t overdo it.

Again, a bit more detail and references at: http://www.thethermalenvironment.com/heat-stress-and-the-risk-of-over-hydration/

These are just a handful of statements that often come up during discussions on the impact of heat and can often cause confusion. Sometimes there is not a clear-cut answer and often variation in the environment and/or the individual can sway the answer from side to the other.