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Heat Stroke Awareness for Trail Runners – First Aid and Prevention Tips

Photo: Courtesy Tambako The Jaguar @

Photo: Courtesy Tambako The Jaguar @


You’re just finishing your run at Government Canyon State Natural Area outside San Antonio. It’s almost 2:00pm and you’ve been running since 10:00am. (It was your husband’s turn to exercise first while you watched the kids.) And you are ready to be done. It’s got to be 104 degrees outside, and your clothes are soaked through. Thank goodness for car seat protectors and air conditioning.

About four miles from the trailhead, you spot someone lying in the shade by the side of the trail. It’s not a good place to take a nap and, as you draw closer, you realize something is wrong with the man lying there. He doesn’t look like he’s napping so much as he’s passed out.

You stop, bend down, and shake him by the shoulder. “Hey, you okay?”

No response.

You shake the fellow’s shoulder again: “Hey there! You okay?”

The man mumbles incoherently. He’s wearing shorts and a cotton t-shirt and the shirt is soaking wet. There’s an empty water bottle on the ground next to him.

So what do you do now?

(Take a minute and think about it. Four miles from the trailhead. You haven’t seen any other runners or hikers for about an hour. You left your cell phone in the car.)

There are lots of things that could be wrong with this person, but the first thing that comes to your mind is heat stroke. (Briilliant!) You remember “brain cooking” and “Heat stroke is an emergency!” from some first aid training you took at some point in your life. “Check ABC’s!” filters through too.

A: You pull the man’s mouth open. Nothing inside besides his tongue.
B: He’s looks like he’s breathing.
C: You feel for a pulse at his wrist. You can’t find it, so you try his neck. Yup, it’s there and it feels very fast.

You’ve got about a half a bottle worth of water left in your handheld. Your hydration pack is empty. You pour the water on the man’s chest and begin fanning him with your pack. “Hey can you hear me?!?”

The man opens his eyes but otherwise does not respond.

Should you run for help?

Before you can decide, another crazy runner training for a summer mountain race comes by. He has a phone!

You call the park rangers and they call 911 and initiate a rescue response.

Knowing how to contact a park’s rangers is invaluable in effecting an efficient emergency response. Put that number in your phone before you run! And while heat stroke is likely in this scenario, the patient could also have suffered a heart attack, a stroke, a diabetic emergency…or… or…etc. With any unresponsive adult, you want to call 911 as soon as possible. You should also assume any unresponsive person in a hot environment has heat stroke until proven otherwise and cool them as rapidly as possible.

The rangers contact 911 and request a helicopter. They are on their way out to you and should reach you in about 10-15 minutes.

Now what?

Your fuzzy memories from that first aid class long ago served you well. Heat stroke is an emergency. The brain is cooking. And your priority is to cool the patient off as quickly as possible to prevent brain damage, organ failure, or death. NOW!

If you can immerse someone in cold water and protect their airway, you should do it. Obviously that’s not an option in this scenario or many TALON trail running scenarios. At best, we’ll usually only have water and ice to work with – and shade.

You pull the hiker further into the shade and pull off his shirt, shoes and socks. The second runner has a full hydration pack (Obviously he needs to read the next installment on dehydration!), and you pour that on the man and continue fanning.

The park rangers arrive with a cooler full of ice and you help them pack it around the patient’s body during the truck ride to the trailhead.

The patient begins to seize. Ranger Niki protects his head and waits for the seizure to pass. She places him on his side in case he starts to vomit and tells you seizures are not uncommon with heat stroke. You help load the fellow onto the ambulance that’s waiting at the trailhead and then walk slowly to the park headquarters to fill in the details of the event for the rangers.

This scenario is based on a real case that occurred in Government Canyon this summer when our temperatures hit 104F. I know you Arizona people are used to those kind of temperatures, but that’s toasty for San Antonio, and while we’re no Houston, it’s humid here – especially in the woods in Government Canyon.

Here are some important pieces to note for us trail runners:

1.  The person who got in trouble was carrying an adequate amount of water and hydrating appropriately.

There is a common misperception that dehydration causes heat stroke. One of the major ways we runners cool ourselves is by sweating. The sweat evaporates from the surface of our skin and heat is lost as it vaporizes into steam. So the logic runs: “If you’re dehydrated, you stop sweating, and your body temperature builds up to 105 degrees F (40.6 degrees C), and your brain starts cooking, your organs fail, and, ultimately, you die. It makes sense, but interestingly, dehydration doesn’t actually decrease your sweat rate “to any important degree”(Noakes, ch. 5). Still, dehydration could affect your cardiovascular system’s ability to cool you down. Right? If you’re dehydrated, your body won’t be able to transport the blood heated by your exercising muscles to your skin where that heat can be dissipated by convection and radiation. Right? Well, not according to any creditable studies says Dr. Timothy Noakes, the renowned South African exercise physiologist and author of the Lore of Running. He reviews these studies extensively in his book Waterlogged: The Serious Problem of Overhydration in Endurance Sports in a chapter appropriate titled “Water’s Role in Thermoregulation.” He concludes, “no study has ever shown that athletes with heatstroke are more dehydrated than those control subjects who complete the same activities but without developing heatstroke”(ch. 5).

PS. My favorite observation in Noakes’ book: “One of the reasons, in my view, why the dehydration myth has been sustained for so long is the natural reluctance of most researchers and clinicians to measure rectal temperatures in large numbers of collapsed and noncollapsed athletes after endurance events”(ch. 3).

That’s not to say, of course, that you shouldn’t carry water on your runs when it’s hot out. Not drinking enough water does lead to dehydration — which is no fun even if it doesn’t cause heat stroke.

2.  The hiker suffered heat stroke and not the runner.

But the runner should have been more at risk, right? He was generating more heat by running – even at his ultrarunner pace – than the hiker was. This incident is a good illustration of how exercise-associated heat stroke results from a combination of factors, not just exercise intensity and ambient temperature. Noakes argues that people who suffer heat stroke likely have a genetic predisposition to excessive heat production. And that predisposition, combined with intense heat-generating exercise, hot ambient temperatures, and maybe a viral or bacterial infection or drug use that interferes with sweating, is what causes heat stroke. Only this kind of compounding factors model can explain why exercise-associated heat stroke occurs “so infrequently and apparently randomly”(ch. 5).

Interestingly heat stroke is rare in marathon and ultramarathon distances. Only six cases have been reported in medical literature. Three of those incidents occurred after 1976. That’s three reported cases of heat stroke at marathons or ultramarathons in the last 36 years! It makes sense when you remember that body temperature is a function of metabolic rate, which is determined by your running speed and your weight. (Noakes, ch. 3). The faster you run, the more heat you generate – and the more heat you need to dissipate Also, the bigger you are, the more heat you generate. (We tiny runners have an advantage at Badwater.) Of course, our bodies are set up to dissipate heat well, and our brain does a fine job at slowing us down when we can’t, so we don’t kill ourselves. The brain forces us to run more slowly and generate less heat. And, ultimately, in the rare instance that we override our brain’s commands to slow down and “the brain temperature reaches a dangerously high level, humans become temporarily paralyzed—unable to move in any coordinated fashion—and therefore unable to continue exercising (Noakes, ch. 1). (Really, if you’re looking to see heat stroke at running events, head to races in 3 to 9 mile range (Noakes, Intro.). These races are short and fast enough that runners can sometimes override the brain’s safety mechanisms.)

3.  The hiker likely survived because he became unresponsive close to the trailhead and could be cooled and evacuated quickly.

Heat stroke victims will die without rapid cooling. And some will die even with rapid cooling (Noakes, ch. 5). Interestingly, because abnormal heat generation is a key factor, effective cooling can take hours. Treat all unresponsive runners in a hot environment as heat stroke victims until proven otherwise, and cool them and get them to a hospital as as rapidly as you can.

Interesting aside: If you see a runner come across the finish line of a race and collapse – or if they get dizzy or collapse when they stop at an aid station – what you’re likely witnessing is Exercise Associated Postural Hypotension (EAPH).

Basically blood pools in their unmoving legs and their blood pressure drops. They feel lightheaded or dizzy, and they might faint. This is especially common in the heat. Conveniently, if they do faint, they’re horizontal and that’s pretty much the treatment for EAPH. Lay the person down and elevate their feet above the level of their heart. If the lightheadedness and dizziness disappear, or they regain consciousness, you’re probably looking at EAPH. Noakes points out that a dehydrated athlete wouldn’t collapse at the end of the race or when they stopped running at an aid station because that’s when the demand on the heart and circulatory system decreases (ch. 2). The dehydrated athlete would pass out while they were running. Of course, you can also confirm it’s not dehydration by asking if the collapsed or lightheaded runner if they’re thirsty. Dehydrated patients are always thirsty. Always. That’s the definitive symptom of serious dehydration: Thirst.

So how do you avoid getting heat stroke as a TALON runner?

Don’t run short races. (Kidding). Don’t run short races fast… (Kind of kidding.)

Alleviate the factors that hamper heat dissipation — and then hope you don’t have a genetic predisposition to excessive heat production combined with a viral or bacterial infection.

  • Give yourself time to acclimate to a hotter environment. Within 10-14 days your body begins to sweat more readily. Your sweat will also become less salty.
  • Run more slowly and take rest breaks.
  • If you’re going to race in hot weather and you live somewhere cool, find a place to simulate running in the heat. Marshall Ulrich wrote a nice piece about sauna training at:
  • Wear loose, light colored clothing. Cotton retains water better than tech material and helps with evaporative cooling.
  • Wear a hat to protect yourself from the sun, and make sure it’s made of a breathable material.
  • Try to run when it’s coolest. Night runs! Pre-dawn and early morning runs!
  • Cover up to protect your skin from the sun.
  • Remember that if sweat is dripping from your body because it’s so humid out, you’re not getting any evaporative cooling effect.
  • Don’t take drugs that interfere with sweating. (No more cocaine-fueled runs.)

Please let me know if you have any questions. And enjoy this last month of hot weather.

– Liza Howard

Works Cited:
Noakes, Tim. Waterlogged: The Serious Problem of Overhydration in Endurance Sports, Champaign: Human Kinetics, 2012. Kindle file.

About the author

Liza Howard Liza Howard became addicted to ultra running belt buckles back in 2008 and now runs for New Balance and coaches fellow ultra runners. She also teaches for the Wilderness Medicine Institute and is a field instructor for the National Outdoor Leadership School. For more information on Liza, check out the About page where you can learn about her coaching, trail running camp, and daily life musings.

One Response to “Heat Stroke Awareness for Trail Runners – First Aid and Prevention Tips”

  1. on 06 Sep 2013 at 9:52 am David


    Thanks for writing such a well written and informative article. It is also very timely for me.

    I am running the Rough Creek Marathon next week and I am a bit apprehensive about the heat. I am currently doing short 3 – 5 mile runs a few times a week in the worst of the heat – 430 to 530, but my longer runs start in morning due to family requirements.

    I am prepared for the distance and the terrain, but my experience with managing heat for this long is limited. I dont normally wear a hat or sunscree but I think I will wear both for this race.

    Again, thanks for the timely information.