If you’ve ever worked or exercised in a hot, humid environment, and you didn’t take adequate rest breaks, you may have gotten to a point where you got goosebumps or chills, you felt light-headed, or even a bit nauseous, and maybe you started to feel weak or more fatigued. What did you do about it?


This is a cue to most people to stop exercising or working, find shade or air conditioning, drink fluids (water), and sit down. The above signs are all signs of heat exhaustion. Heat exhaustion is typically the point where your cardiovascular system (your heart and blood vessels) can no longer support the work you’re doing. Remember how your heart rate is higher when working in a hot (vs. a cool) environment? (see here for a refresher!) Well, your heart rate can only increase so much, and you also have a finite amount of blood that can go to your working muscles for energy and to your skin to cool you off.

When you reach this “maximum” point with your cardiovascular system, you will feel symptoms of heat exhaustion: weakness, fatigue, faint/light-headedness, really hot skin, very sweaty, potentially vomiting, and difficulty working or exercising.

These are all signs that you should:

  • Stop working immediately
  • Find shade or air conditioning
  • Remove extra clothing (to help you cool down faster)
  • Elevate your feet (to help return blood flow)
  • Use ice-cold towels to help cool you off
  • Drink plenty of fluids

You should start to feel better within 10-15 minutes, and can return to work. But take care— you may need to slow down your work rate or take extra breaks throughout the rest of the day to avoid experiencing heat exhaustion again (or other heat-related injuries).

Exertional Heat Stroke

Exertional heat stroke (EHS), on the other hand, is a serious medical emergency, and if not treated properly can result in death. But the good news is that EHS is 100% preventable.

It is important to remember that heat exhaustion does not precede EHS. What does that mean? Simply put it means that Heat Exhaustion and EHS are two separate things…. someone won’t necessarily experience heat exhaustion before getting EHS.

Often, EHS can come about very suddenly, without any signs or symptoms.

There are 2 main ways to diagnose Exertional Heat Stroke:

  1. A core temperature >104°F or 40°C. And the only real way to differentiate between heat exhaustion & EHS is to measure core body temperature (with a rectal or esophageal probe).
  2. Central nervous system dysfunction, such as hallucinating, behavior changes (e.g., aggressiveness, irritability, confusion, irrational behavior), weakness or inability to work, collapse/fainting.

[Note: The person may also experience vomiting, hot & sweaty skin, and fatigue, but the behavior changes are the key clue that the person needs serious medical attention and emergency cooling.]

And lastly, if someone is experiencing EHS, call 911, and in the meantime cool them down quickly (ideally using an ice bath), and do not leave their side.


  • Use a buddy system at work to check on each other. Try to talk to a buddy (that you know fairly well) sporadically throughout the day to check in. If you notice personality changes in your buddy, take immediate precautions to get them rest, shade, and fluids, and seek medical attention (if you suspect EHS).

  • Pay attention to your own symptoms. You will not be able to “push through” a heat illness. Being “tough” in the heat will not get you anywhere but passed out on the ground or in the hospital. Take any warning signs/symptoms seriously. When you notice that you feel “off”, take a break, drink water, and remove extra clothing to cool down. You will be much more of a hero if you can complete your work for the day and stay safe.
  • Be vocal. If you’re not feeling okay, let someone know immediately- don’t wait until it’s too late.
  • Listen to others & take them seriously. If someone tells you they’re not okay, encourage them to take a break and rest. Help them find water & shade if necessary. Check on them in 5 min to make sure they’re doing better. If they’re not feeling any better after 10-15 min, seek medical attention right away.

For help with heat safety training and setting up emergency cooling procedures at your site, check out Kenzen’s heat safety program.

Reference: Quick Questions in Heat-Related Illness and Hydration: Expert Advice in Sports Medicine. National Athletic Trainers’ Association & SLACK Inc., 2015. Editor: Rebecca M. Lopez.

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