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A Close Call with Heat Exhaustion

Walking down Rt 2 towards the Northern Presidentials
Walking down Rt 2 towards the Northern Presidentials on Hot Black Top

I didn’t put two and two together when I was experiencing the symptoms of heat exhaustion during a high exertion hike last week, but after a friend pointed it out to me, I realized that I’d had a close call.

While I’d taken precautions against the sunlight and heat such as drinking plenty of water, monitoring my urine color, eating salty foods, wearing a hat, and loose-fitting, well-ventilated, and lightly colored clothing, the location I’d been hiking in had put me at high risk.

For example, I’d hiked 8 miles of black-top and a cinder covered rail trail during the middle of a hot sunny and humid day, followed by a 3000 foot climb up a steep mountain with a 30 pound backpack. The following day, I hiked another very strenuous 6 miles above treeline in full sunlight, where I could feel the heat reflecting off the boulder fields I had to traverse.

I’ve hiked the same and similar routes previously with no ill effects, so I really didn’t think I was at risk. I was drinking plenty of water, eating salty food during the day and felt that I was staying ahead of the salt depletion and dehydration curve.

Still, I experienced a few symptoms that I should have paid more attention to such as gagging on food during meals, loss of appetite, and mild stomach cramping. At the time, I wrote these off to a case of nerves because I was hiking over a highly exposed section of trail where I’d had a close call the previous summer in a thunderstorm, with lightning and hail. It never crossed my mind that I was suffering from a heat-related illness.

Heat Exhaustion
Heat Exhaustion

Heat Related Illnesses and Hiking

There are three levels of heat related illness that hikers should be concerned about in hot weather: heat cramping, heat exhaustion, and heat stroke.

  • Heat cramping occurs when you become dehydrated and experience leg or abdomen cramps and sweat more heavily than normal.
  • Heat exhaustion can occur after you’ve been exposed to high temperatures for several days. Symptoms include heavy sweating, weakness, dizziness, dark-colored urine, fainting, fatigue, confusion, muscle cramps, nausea, and weak pulse.
  • Heat stroke (sunstroke), the most dangerous heat related illness can be fatal and requires immediate hospital treatment. Symptoms include throbbing headache, confusion, nausea, dizziness, shallow breathing and unconsciousness.

Given the overlap in the symptomatology, it can be difficult to differentiate one level from the next. The difference between them is a matter of degree, particularly in your body’s ability to self regulate its temperature and how fast you can recover. For example, you can usually recover quickly from heat cramping by properly rehydrating, but heat exhaustion may take several days or even weeks to get over.

Heat Exhaustion

Given my symptoms, I figured my condition  fell somewhere between heat cramping and heat exhaustion, but was getting progressively worse as I continued hiking without any extensive rest breaks or a day off.

Once I got below treeline and off the baking rocks of the Northern Presidential mountains, I sought out a shady camping spot in the forest near a cool stream. There I washed three days worth of sweat off my body (LNT style), more to get clean than to cool off my body, even though that is a recommended treatment for heat exhaustion. After bathing, I continued to experience nausea while trying to get some dinner down and then had to struggle to stay awake until nightfall.

Treatment for Heat Exhaustion

The primary treatment for heat exhaustion is to rest in a shady spot or, better, an air-conditioned room, and to drink cool water. You can lower core body temperature by immersing yourself in cold water or spraying yourself with cold water and fanning. Water is usually enough to reverse dehydration, but electrolyte-enhanced sports drink can also be helpful for recovery. If you don’t feel better within an hour, it’s recommended that you seek medical treatment which can include rehydration via intravenous fluid and more aggressive cooling using ice blankets and cold water immersion.

Preventing Heat Exhaustion

  • The best way to prevent heat exhaustion is to prehydrate before a hike and to drink plenty of fluids in hot weather. Rather than drinking a lot of water at once, it’s best to drink a few sips very frequently. During periods of intense exertion, such as hiking up a steep trail in hot and humid weather, your body can lose 1 quart of perspiration per hour.
  • Hike early in the day and seek routes that are well shaded from direct sunlight between the hours of 10 am and 4 pm.  It will still be hot in the late afternoon, but less hot than during mid-day.
  • Wear loosefitting, lightweight, and lightly colored clothing that doesn’t hold in the heat and helps your body cool properly by sweat evaporation.
  • Eat salty foods such as chips or nuts to replace electrolytes than be lost by sweating. Electrolyte drinks can also be helpful.
  • Wear a wide brimmed hat or carry a trekking umbrella to help avoid sunburn. Sunburn make it harder for your body to cool itself. Cover up with light, loose clothing or wear sunscreen.
  • Scale back the distance and elevation gain you tackle on hot days. Take longer breaks and drink plenty of fluids while resting.
  • Monitor your urine. If you’re properly hydrated you should be peeing frequently and your urine should be clear. If your urine is a darker yellow, you need to drink more.

Have you ever experienced heat exhaustion?

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31 comments

  1. A friend of mine swears by Pedialyte, which I’ve never tried. On a group hike she was on, someone was experiencing heat-related difficulties, and they gave him Pedialyte and he recovered very quickly. Not sure the difference between that and Gatorade, really, but now she carries powdered Pedialyte on all her hikes, just in case.

    Pedialyte Powder Pack, 8 Count

    Also, I know you did mention this, but in some running articles I’ve read recently they say that keeping your skin cool actually helps more than keeping your core cool. So sitting in cool water or spraying cool water on yourself may be more effective that just staying hydrated (which of course you should also definitely do).

    I’ve been lucky to not (yet) experience heat exhaustion so these are both anecdotal, not from personal experience. Heat exhaustion doesn’t sound like much fun, though. Good thing you were smart enough to stop hiking before it got too dangerous for you.

    • The issue wasn’t dehydration but core body temperature. I was drinking plenty but over exerting in high heat and humidity. They’re obviously related though, but let this be a lesson, at least, for me, that hydration is not enough. Like hypothermia, ie the mumbles, heat exhaustion can be very hard to recognize when hiking alone.

      • re: the mumbles

        Just one of the Umbles siblings … the other two are stumbles and and fumbles. You are dead on, they are difficult for the self diagnoser to recognize

      • The same thing happened to me yesterday. 37C and I hiked a familiar but challenging trail, a fair bit of it in the sun. I noticed that my pace was extremely slowed by the heat, and I thought I was drinking enough water, but clearly I didn’t. Also ate salted nuts along the way, thinking this would help. I was sweating profusely, which didn’t alarm me, because of the terrain and the heat. But then I started feeling nauseous and my jaw muscles started clamping, and I noticed that even though I was sweating I had the shivers. I was hiking alone, but had reached a gorge with a stream running through it. I was able to find a shady spot and cooled myself in the water. Rested for quite awhile, and then slowly made my way back to civilization. I was also hiking alone and have been hiking for the last 25 years. Never had this happen to me before, and I feel a little embarrassed. But nothing like the absolute exhaustion I’m struggling with today. Giving my body a few days rest for now, but already planning my next route.

  2. I have done several hundred miles of Desert hiking, but the closest call I ever had with heat exhaustion was my first time on the Franconia Ridge Line.

    It was a very hot and humid day and we ran out of water just before MT. Lincoln and had no way to get out of the sun. My wife and I were new to “real hiking” and it was a foolish mistake we never made again.

    Thankfully, we made it to the Green Leaf Hut and stayed for about an hour before returning to the parking lot.

    I’ll never forget the anxiety we felt during those 3 or 4 miles. We had read about all dangers of being exposed above Tree Line. We were prepared for Hurricane winds, hail, rain and snow, but I never imagined the sun being our worst enemy.

    I always caution newbies to the White Mountains that being exposed above tree line doesn’t just put you at risk during bad weather, but you can be at risk during great weather. It’s similar to hiking in the desert in the sense that there is no way to get out of the sun and few places (if any) to refill water. The high winds evaporate your perspiration and you can find yourself in a dangerous situation even on the most beautiful day.

    • Interesting experience. I was just up there and loaded up on extra water at Liberty Spring because that section over Lincoln and Lafayettee is dry. But you can really feel the sun’s heat bouncing up at your on a hot day from the rocks. Like walking on hot pavement. And you’re right. You don’t even know it’s happening because the wind drys you off.

  3. Phil,

    Great article. Great reminder. I myself just experienced dehydration with severe cramping in my quads during an attempt at Mt Isolation this past week. I bagged it about 5 miles in; just 2 miles shy of the summit. Then I began to drink profusely and by the time I had returned to my car I consumed a total of 8 liters. Little did I know at the time, overhydration is also a concern. I suffered significant stomach cramping on the ride home (thank goodness my wife was driving) and I ended up vomiting loads of water. Dehydration and overhydration are equally as dangerous I’ve learned.

  4. I had an experience with it at age ten during a very hot Dallas summer–aren’t they all? My brother and I were building a tree house at the creek about a half mile from the house. There had been a number of deaths in Dallas that summer from the heat. I started getting very weak and all I wanted to do was lie down for a nap but I was aware of what was happening and knew if I took that nap, I’d never wake up. I got on my bicycle, struggled home, stumbled through the front door and collapsed in the living room. My mother was a nurse and she took care of me.

    Four years ago, I was hiking with a friend in west Texas when he started showing symptoms. It’s scary when there’s no shade whatsoever and you are a long way from any relief. We did our best to try to shelter him as we made our way to the trailhead but we weren’t well prepared. We did make it safely and he fully recovered after a couple days. After that incident, I bought a GoLite Chrome Dome hiking umbrella.

  5. I have found that with open summits, the sun boiling down on the rocks can be a real problem on an extremely hot day. The heat coming back up off the rocks is like being in a frying pan. As I get older I try to hike areas that have a canopy of trees when possible.

  6. 3 thoughts on food:

    The salt makes you thirsty which is great. Even on hot days if i’m really trying to focus I won’t drink enough. The salt stimulates thirst which is great.

    People always talk about trail mix or chips as good salty food due to taste but those are often high in fat. Personally I can’t handle alot of fat in my hiking diet…not sure why but for now I have to accept it for now. If you buy the right brand you can find pretzels that have a ton of salt and are low in fat. I think i had some that were <5% fat which makes it all carbs that are great for fueling a long day.

    Store your food in a non-readily accessible compartment if you are concerned about going to fast. This way you have to stop, take off your pack, unpack some and get it out. Ofcourse the flip side of this is you may just neglect your food all together but its something to think about.

  7. I always like the part where I seem to black out for a second or too and half to fight to stay focused. Was a problem for me during the many Desert Hikes in the Marine Corps and then on my own for some 31 years. And now that I live in the South it actually more dangerous with the humidity making you sweat so much to cool down where as in the Desert you barely feel the sweat evaoprating so you just naturally force yourself to drink more…I remember licking my skin and liking the taste of the salt. I used to force myself to take two Salt Tablets with each quart or canteen of water, I forced myself because the salt did not make me feel well at all, so it was a forced issue. Later Science discovered Salt wasn’t doing that much good for you….For the last 28 years or so I have using Gookinade which is now called Vidalyte created by a San Diego Cardiologist, I can’t find it here where I live so I have been using a pill form again I buy from an internet source it is called Heat-Aid electrolyte tablets, Sodium Free, Sugar Free. take with 8 ounces of water. Today as most days, I am working outside and was feeling poorly so I took the two tablets which come in a sealed pack..and I felt better in 20 miniutes…The real secret to prevention is to drink 4 ounces every half hour and if really sweating 16 ounces every half hour, I find that works for me..

  8. I was told that once you have experienced heat exhaustion that you are more susceptible to it. in addition to hydration and electrolytes, I have found that frequent wetting of my hair, hat, shirt collar, and wearing a wet scarf or towel around my neck helps a great deal. the gagging and/or vomiting, yes, I have also experienced that.

  9. Out here in California heat exhaustion is a big issue. I get around it by drinking plenty of water before I leave, carrying a full Camelbak and drinking it, and backing it up with an extra two bottles of water just to be safe. I sweat a lot so my wet shirt keeps me cooler than most. I avoid going out in the middle of the day for long hikes and I avoid narrow canyons where the wind cannot blow.

    I had one bad experience with heat exhaustion where I broke several rules. I was aiming for a 5000 footer called Bedford Peak via a grinding set of switchbacks called The Silverado Motorway. Some motorway: no car could manage its narrow track. We got about half way up, then I ran out of water and the soles of my wife’s boots melted off. That’s right. They melted off! We turned around, but on the way I started vomiting. Luckily we were positioned just right for a cell phone signal and called 911. The county sent in a helicopter with a rescue crew. One piece of advice for those in rescue situation: always carry a space blanket. It was the best $5 I ever spent. We laid it out near me. The rescue crew told me that they had no clue from my description where I was, but as soon as they saw the space blanket they were able to land within twenty yards of my location!

    I spent the rest of the day being hydrated at a local emergency center. Since then, I have avoided strenuous hikes on hot days and always carried more water than I thought I needed. I also carry salt tablets which can help when I’ve been sweating a lot.

  10. One of the other troubling things with heat stroke is that you don’t have to have heat exhaustion first. The problem is heat stroke is that the body has lost the ability to thermoregulate. This results in body temperatures greater than 104F (40C) and people will become profoundly confused or unconscious. They can also have seizures.

    Sweating is a important process the body uses to maintain body temperature, so if someone stops sweating is a bad sign. Confusion is also a very important sign. Normal healthy people should make sense, so if someone starts not acting right it is time to stop and rest.

    Treatment wise it is always important to get the person out of the heat source (i.e., the sun in most cases). If they are able to follow commands have them drink some water (preferably something with a little salt and sugar). Cooling in the wilderness may involve getting clothing wet or at the point of heat stroke (which require immediate cooling) submerging the person up to their neck in water (if available).

  11. Once I got heat stroke just power washing my house. We had rented a washer from Home Depot for a day, it was in the 90s out, and I drank over a gallon of water. At some point I realized that I was feeling bad and was confused about how to put the two ladder sections together (which is really easy to do). Took my temperature and it was 102F. Got in the tub, temperature went right down. I stupidly went to finish the power washing (only had a few hours before it was due back at Home Depot), and my temperature went right up again.

  12. Evaporating Water is much more efficient as a coolant than sweat. On these hot backpacking day, I douse my shirt in a flowing stream every hour or so. By the time I get it back on my body it is so cold I shiver. On the AT streams are often hard to come by, so I carry a gallon Ziploc, put my shirt in the Ziploc, and add about 10 oz of water. The shirt gets wet, and I don’t lose any water spilling onto the ground. I experienced heat exhaustion my very first strenuous hike after moving to the East, and I never want to go through that again!

  13. With daylight saving, especially out here in Oregon where we’re at the eastern edge of our time zone, the peak temperature of the day in midsummer occurs between 5 and 6 pm. Of course as the days get shorter in August, the cooldown will start a bit earlier. I think those 10 to 4 hours were developed before daylight saving! Around here, the hottest part of the day is more like 11 am to 7 pm. Of course that gives us more time in the morning! What I do in hot weather is to get on the trail at the crack of dawn by nautical twilight standards (currently 4 am here) and hike until noon, then hole up in the shade for the rest of the day. If necessary, another 2-3 hours can be hiked in the evening. I actually started this practice when hiking with my dog (dogs are far more prone to heat exhaustion/stroke than humans), but it works for me, too!

    I also find an electrolyte solution almost essential. It isn’t just salt that is needed, but other minerals (potassium, magnesium, calcium) along with it! Without the electrolyte solution, everything I drink seems to go in one end and out the other and I’m still thirsty. With the solution, I actually need less water and feel both less thirsty and more energetic.

  14. What an excellent article. I had heat exhaustion last week and it lasted for 3 days. It was like being really hungover or the first month of pregnancy feeling. So something you want to avoid. I will be posting this article for others to read. The comments are great as well.

  15. Thank you for the helpful info, oddly enough it was the first email update I viewed after completing our counter-clockwise Rae Lake Loop yesterday.

    My wife and I both experienced mild cases of heat exhaustion as we finished up the last 5 miles of our 23 mile day. I knew it was going to be hot as we came down in elevation so we started at twilight. Unfortunetly I did not expect to go through so many humid swampy sections and then right back to exposed granite stairs, that was a tough combination.

    Evaluating heat exhaustion in myself has always been difficult. I do not sweat very much to begin with and I seem to skip all of the normal signs and go straight to nausea and of all things water will do it for me (lucky me). So I too will soak my shirt, hat, hair and even wetting my legs. I also find that the power aid electrolyte water supplement works extemely well, for me anyway. Somehow I do not feel qweezy when I drink it and I bounce back quickly.

    The next challenge is trying to keep an eye on my wife and making sure she is safe. I had her read your post so she could understand the symptoms herself. I appreciate the suggestions by others as well and will look into the pedialyte.

    I think the most important thing you can do when hiking with others is making them feel comfortable enough to admit they don’t feel well. Too often they will ignore symptoms or obvious signs that something is wrong just so they are not that “one guy in the group”

    Thanks again for the tips

  16. I’ve learned a few things about dealing with the heat, since moving to Texas
    1) Pre hydrating is very important for me.
    2) When I feel water sloshing in my stomach, it is because I didn’t have enough electrolytes to allow me to absorb the water. Drinking more water will NOT help at this point. I like G2. (from Gatorade). Alternate G2, Water, G2, Water….
    3) Wide brim hat, with a wet bandana under the top part, works well for me. Since I’m bald, I don’t go to the mailbox without a hat in Texas.
    4) coolmax type fabrics work for me. (cotton is rotten).
    5) those gel things, you soak in water for 15 minutes, and tie around your neck, also work for me. Cools the blood to/from your head. A wet bandana around your neck works well, but it dries out very quickly.
    6) endurolytes (by Hammer, usually at bike shops) are electrolytes in a pill form. They worked well for me, but hard to adjust the dosage since you don’t taste the salt. Be careful if you are susceptible to kidney stones.
    7) if it’s above 100, or over 90 with high humidity, just avoid being outside in hottest parts of day.

    One time when I was overheated, and dizzy, a friend told me to drink pickle juice straight from the jar. It is a salty brine, you can digest very quickly. Sounds awful, tastes great when you are depleted (as I was). I felt 10 times better very quickly.

    Hope none of these are duplicates from above, as I didn’t have read them all.

  17. I too suffer from heat related symptoms on long hikes. A pharmacist recommended Pedialyte solutions. I haven’t had leg cramps on hikes since started this solution. Water just doesn’t do it. I’ve tried all kinds of tablets, salt shaker, and was doing well with dill pickles but the Pedialyte has been the best. I will look up the Gooklinaid/Vitalyte but unsure if I really need to change solutions. The neckscarves that have gel in them work great for wearing around the neck and a wet bandana/and or hat in the sun help too. I really liked this article and the comments. I have been searching for this type of info since I started hiking the 4000 footers of NH. This week I completed 6 of the 4000fts in Maine, and was without leg cramps! Finally. Thank you.

    • Update: I finished hiking my 67 highest in New England last week, in Baxter State Park. I did have leg cramps by the time we reached our second peak of the day, Hamlin. I used powdered G2 in my water bottle and was able to get the leg cramps to subside. Pedialyte seems to work the best, but I had not carried any on this hike, feeling like the powdered G2 would be enough. My suggestion is to alternate electrolyes with water all day during your hike, as Katahdin Dave said above. Keeping cool, hydrated and using electrolyte solutions: best I’ve found is the Pedialyte, pharmacist’s recommended to me. It is more that just salt loss. Potassium, magnesium etc is needed. Drinking more water doesn’t help if you are depleted from your electrolytes. The comments above are very helpful to me for learning the tricks of the “hiking” trade! Thanks.

      • You right on the money with regard to replenishing potassium, magnesium and other electrolytes. Bringing Pedialyte is a very good suggestion.

  18. I can’t thank you enough for this!

    Over an abnormally warm and humid Memorial day weekend this year I tackled ~25 miles of back country trails located in the 100 Mile Wilderness in two days. Only about 7 of these miles were on the AT – the others were some fairly rugged miles.

    I incorrectly estimated my next water source (maps were not good in this area) and had to hike ~2.5 miles without water over the hottest part of the day. Shortly there after I extremely very nauseous and began vomiting. I had initially attributed to Giardia as my water filtering procedure wasn’t perfect, but I’ve now learned that has an onset period of a week or two.

    I felt like I’d nailed down my water filtering procedure on subsequent hikes but was still dealing with slight nausea throughout the day and at diner time. After reading your article, doing some Google-ing, and reviewing my diet over the hikes, I’m fairly certain I’m not getting enough sodium.

    Thanks again Philip – I return to your site often as a good and reliable source of information.

  19. Heat exhaustion can slip easily into heat stroke. I had mild heat stroke decades ago in my early 20s and learned that getting immersed in cool water is very important to cool down the body quickly, especially if you are far from any kind of medical assistance. Here is what one of my docs told me: If you are not near a source of water, then learn to carry one or two of the chemical packs that upon hitting, will create a cold pack . Wrap the pack in one layer of cloth to avoid damage to your skin and gently apply it to your neck and up and down your limbs. Besides drinking it, pour some of your carried water on your head The Pedialyte solution is also useful. Sometimes older folks wonder just how much salt they should eat, especially when a doctor has told them to lay off the chemical. As always, consulting with your doctor about your outdoor activities will help the physician gain some perspective and make some suggestions that are germane to your particular activities, as the above suggestions are to mine.

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