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3 reasons why preventing heat illness might just prevent getting a concussion in the first place

For sports, military, and workplaces

Read to me! Audio here:

DIY your sport drink recipe. 2 cups of water plus 2 cups of your favourite real fruit juice plus /4 teaspoon of salt. Mix, chill and enjoy when you need the extra electrolytes.

The temperature is coming down a bit. It’s going to just hover above 30 degrees Celsius (86 degrees Fahrenheit), which is much better than the 44 degrees Celsius (just over 110 degrees Fahrenheit) from last week! Yet I’m still thinking of last week’s extreme heat when I saw someone jogging in full sun. Then I think of the military personnel I often see downtown, walking around in their uniforms, carrying what looks like a heavy backpack. And it’s summer, which is also colloquially known as “construction season,” and everywhere I go I see city workers doing physical labour, around machinery.

A person working construction in the sun on solar panels

In my last post I answered the question “Why are my TBI symptoms worse in the heat?” Because indeed, the heat takes a toll on our injured brains. But today, I wonder about those without a brain injury — are they at higher risk of getting a concussion, or a worse concussion, when doing physical work in the heat? Turns out there’s some evidence that when it comes to athletes, military, physical labourers, and just about anyone doing strenuous activity in warmer climates, the answer is YES.

From athletes dropping on the field, to spikes in heat illness at the outset of military service, to deaths on the job or during sport practice, organizations need to take heat illness seriously with active policies and plans in place.

Dandelion flower growing through the cracks of dry soil

So cancel your hot yoga session, grab some shade, and take a water break, we’re going to look at why keeping people safe from heat illness is important specifically in preventing concussion and long term symptoms.

1) When the body overheats, this impairs the brain — less functioning brain means higher risk of accidents

In my previous post I shared how the brain is particularly vulnerable to the heat — it doesn’t cool down as fast as other parts of the body.

That heat can come from outside the body, like from the sun, hot weather, and humidity. Heat also comes from inside the body when you are physically active — when the muscles are working, a lot of that energy gives off heat.

Sunglasses on Sand under a strong sun

Whether heat comes from outside or inside, that heat is stored in the body, which raises your internal body temperature until the heat can be released. A common way your body gets rid of that heat is through sweating.

The body likes to stay around a temperature of 37 degrees Celsius. Exercise alone can increase body temperature to 39° or 40°C, and it can stay that high up to 3 hours after exercise has stopped. Body temperature can rise higher and quicker in hot environments. Plus high humidity prevents your sweat from evaporating, which makes it harder for you to cool down.

Two people hiking with large backpacks looking warm and tired

Body temperatures above 37°C can lead to brain fatigue, dizziness, nausea, malaise, headache, etc. Above 40°C more severe cognitive and neurological issues can show up like delirium, loss of consciousness, seizures and yes, brain damage.

The impairment heat has on the brain puts an athlete, military personnel, physical labourer (or jogger!) at risk of falls and accidents that can cause a head injury. Indeed one study showed higher incidence of TBI in military patients with high body temperatures (Wade et al., 2011).

Lower risk of head injury by keeping your people cool.

2) A high body temperature at the time of a head injury can lead to more cognitive and neurological problems post injury

It’s been a common practice in intensive care units to cool down patients who come in with moderate to severe brain injuries. For example, fever can happen after a stroke. If that fever isn’t dealt with patients seem to have worse outcomes. Cooling is thought to lower neuroinflammation, cell death and damage to axons in the brain.

So the question: is this also true for mild TBIs and concussion?

Canadian football player being tackled by another football player, and a helmet has come loose

There’s still more research to be done, but so far pre-clinical and animal studies show that a high body temperature, causing a hot brain, leads to more neuron loss and worse cognitive problems after a mild TBI. Plus, cooling down the animals in these studies post mild TBI prevented some cognitive problems and damage to the brain (Atkins et al., 2017).

So for athletes, military, and workers who might already be at risk of getting a hit to the head, when you add heat, you add more chance that the injury will cause longer more serious problems.

Lower risk of longer and worse brain problems by keeping your people cool.

3) People who have had a concussion in the past may be more susceptible to heat illness

So you’ve recovered from a concussion. You’ve been given the ok for return-to-play or return-to-work… does that mean that things are back to the status quo??

Woman get a large splash of water in the face

There are a number of factors that can put someone at higher risk of heat illness: poor physical fitness level, lack of heat acclimatization, lots of clothing, poor sleep, recent stomach flu, diabetes, high blood pressure, medications like aspirin, beta blockers, antidepressants, a well as things like alcohol, illicit drugs and maybe even caffeine.

Some research is now also suggesting that a previous concussion can be a risk factor for heat illness.

One study looked at 100 NCAA university athletes (Alosco et al., 2017). They found that athletes with a history of concussion reported more symptoms related to heat illness than athletes with no history of TBI. What’s extra interesting is the authors suggestion that the higher reports of heat illness symptoms might come from problems with the Autonomic Nervous System (ANS) post TBI.

Two women playing softball on the ground, sliding into the base, one is not wearing a helmet

The ANS in your body is responsible for regulating all sorts of things you don’t have to think about like heart rate, blood pressure, digestion, focusing the eyes and controlling the body’s temperature. There’s evidence to show that the ANS doesn’t always work in tip top shape after a mild TBI. In fact, changes to the ANS post injury can still be there even after symptoms have gone away! (Esterov & Greenwald, 2017)

In other words, a person post concussion may seem fine on the outside, but may still be healing on the inside. And for temperature control, this means an otherwise fully functional human returning to play or work may still be at risk for heat illness, and another concussion.

Construction worker standing underneath a low metal ceiling with no helmet

Prevent re-injury by accommodating those with TBI history to make sure they stay cool.

Oh my gosh, I had no idea there were so many links between heat & TBI! How can I keep my athletes, military personnel and workers safe?

In my last post I shared links to health resources for preventing heat illness. Here, let’s go one step further and comment on policies and plans organizations can have in place.

Follow your industry’s best guidelines

Construction worker Writing on a clipboard on Top of Table

It is beyond my scope to tell you which guidelines are best for preventing heat-related illness in your field. But let me point you in some helpful directions 🙂

Here are some resources. I’m not saying these are exactly what you need, but they provide some examples:

Considerations for the development of extreme heat policies in sport and exercise

  • Journal article summarizing the most updated research on heat policies in sport

Heads up football: Heat and hydration guidelines

  • From the University of Connecticut
  • An example of heat acclimatization guidelines and hydration for American football

Heat Illness Resources: Army Public Health Center

  • Prevention
  • Risk management
  • Work/rest time charts
  • Fluid replacement
Military woman

Managing heat stress at work

  • From the Government of Ontario
  • Illnesses due to heat stress
  • Ways to manage in the workplace
  • Creating a heat stress plan

Criteria for a Recommended Standard: Occupational Exposure to heat and Hot Environments

  • From the Department of Health and Human Services, Centres for Disease Control and Prevention and the National Institute for Occupational Safety and Health
  • A long document of standards and basis for these

Extreme Heat Events Guidelines: Technical Guide for Health Care Workers

  • From the Government of Canada
  • A very lengthy yet comprehensive document
  • Includes physiology, risk factors, medication lists, summary for medical officers, and fact sheets

Heat Stress: Cool Solutions

  • From the United Food & Commercial Workers Union
  • More information on heat illness affecting workplaces
  • What laws and regulations there are in Canada and what they are missing
  • A quick reference table with humidity levels and the needed response plan 

Heads-up: What you need to know about concussions in the workplace:

  • From the Canadian Centre for Occupational Health and Safety
  • Preventing and managing concussion at work
Woman Wears Yellow Hard Hat working in an automotive shop

In a nutshell, these guidelines suggest things like:

  • Heat acclimatization protocols
  • Planned cooling strategies
  • Reducing work and intensity in hot/ humid temperatures
  • Avoiding the use of heavy equipment or apparel until heat acclimatized
  • The hotter and more humid, the more breaks that are required
  • Access to cold water and other cool beverages
  • Educate trainers, coaches, leads, and staff on the signs, symptoms and consequences of heat illness, especially when physically active
  • An emergency plan for heat illness, and the ability to put this plan into action
  • Knowing concussion signs & symptoms. When in doubt, sit them out.

A note on water — can you drink too much?

Clear Drinking Glass of water

This is a question that comes up, and the answer is technically yes, though rare.

In general if someone drinks more water than they are sweating, that water intake can sort of dilute the blood. This is rare and dehydration is far more common, so far more of a concern. But it’s an easy fix — all you need to do is add some electrolytes and the easiest electrolyte to come by is salt.

Whether it’s through a snack during break or in your sports drink, a little bit of salt can go a long way. The salt helps absorb some of that fluid and makes you want to drink more too.

It doesn’t take much. Here’s a recipe for a homemade sport drink that’s easy on time and budget:

2 cups of water

2 cups of your favourite real fruit juice

1/4 tsp salt

  1. Mix altogether in a 1 litre bottle or jug.
  2. Chill and drink when needed!

And what about the children?! Youth are more prone to overheating

Have you ever heard someone say if you’re thirsty then you’re already dehydrated? Well, this is especially true in youth. Kids produce more heat when exercising and don’t sweat like adults, so kids can have a harder time cooling down. Offering up cold drinks, having chilled water on the sidelines, and sometimes that homemade sports drink can encourage them to drink more when they are distracted by play.

kid drinking from a water bottle with ice in it

If this seems like a lot, I know, it is. But addressing heat illness not only helps prevent head injuries and their potential for long term problems, but these preventative measures also set a person up to get more from their training, and overall stay healthy at work.

Let’s all stay cool 🙂

Krystal Merrells, RD

Additional References & Resources

Alosco, M. L., Knecht, K., Glickman, E., Gunstad, J., Bergeron, M., & Hart, J. (2012). History of Concussion and Exertional Heat Illness Symptoms among College Athletes, International Journal of Athletic Therapy and Training, 17(5), 22-27. Retrieved Jul 15, 2020, from

APA Armstrong, Lawrence E. Ph.D., FACSM (Chair); Casa, Douglas J. Ph.D., ATC, FACSM; Millard-Stafford, Mindy Ph.D., FACSM; Moran, Daniel S. Ph.D., FACSM; Pyne, Scott W. M.D., FASCM; Roberts, William O. M.D., FACSM Exertional Heat Illness during Training and Competition, Medicine & Science in Sports & Exercise: March 2007 – Volume 39 – Issue 3 – p 556-572

Atkins, C. M., Bramlett, H. M., & Dietrich, W. D. (2017). Is temperature an important variable in recovery after mild traumatic brain injury?. F1000Research6, 2031.

Burke, L., Deakin, V. (2006). Clinical Sports Nutrition 3rd Edition. Chp 17 Nutrition for special populations: Children and young athletes. McGraw-Hill Sports Medicine Series.

Esterov, D., & Greenwald, B. D. (2017). Autonomic Dysfunction after Mild Traumatic Brain Injury. Brain sciences, 7(8), 100.

Nelson, D. A., Deuster, P. A., O’Connor, F. G., & Kurina, L. M. (2018). Timing and Predictors of Mild and Severe Heat Illness among New Military Enlistees. Medicine and science in sports and exercise, 50(8), 1603–1612.

Nichols A. W. (2014). Heat-related illness in sports and exercise. Current reviews in musculoskeletal medicine, 7(4), 355–365.

Sports Dietitians Australia. Fluids in Sport. Accessed July 20, 2020

Wade, C. E., Salinas, J., Eastridge, B. J., McManus, J. G., & Holcomb, J. B. (2011). Admission hypo- or hyperthermia and survival after trauma in civilian and military environments. International journal of emergency medicine, 4(1), 35.