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Flirting With Heat Exhaustion on Today’s Run

There’s a fine line between being tough about your training and being stupid. I crossed that line today, then continued to run a bit further.

I had 8 miles on my schedule, but honestly had not thought to look at the weather report this morning. I was working in my air-conditioned office at the clinic all day and never stepped outside. Around 2:30 I decided to head out for my run. When I stepped outside it felt pretty warm, not oppressively hot, but warm. My plan was to run a bit over a mile to a trail head, then do 4-5 miles on some tough trails, and finish with about 3 miles on the road back to the office.

About a quarter mile into the run I realized that it was indeed pretty hot, and that I had not brought along any water. “It’s only 8 miles” I told myself, not a big deal. That was the moment that I crossed the line into stupid-land.

I made it to the trailhead without incident, then had fun running the switchbacks up and down the hills through the woods. It was cooler under the trees, but it was tough going and I did notice that my mouth was getting really dry. But I was determined to get in the full eight miles. Another dumb decision.

I emerged from the forest around mile 5, and once I hit the asphalt I started to feel weak. For the next two miles I had no tree cover and I was baking in the sun. My legs felt completely fried, and it was a struggle to not walk. I was dying for some water, though I was still sweating plenty and did not feel dehydrated. Fortunately at mile 7 I reached a local park and found a water fountain. I drank a bunch, poured a bunch more over my head and legs, and managed to struggle through another mile and a half to get back to the office. I had absolutely nothing left, my legs didn’t want to move.

When I got in my car to head home the thermometer said that it was 88 degrees out. It was probably hotter where the direct sun was radiating off the asphalt. I honestly had no idea that it was that hot, but it explains a lot. That’s by far the hottest it has been so far this year in NH. For the next few hours I felt light-headed, occasionally dizzy, and weak. I had to leave the dinner table to go lie down. My legs felt shaky.

My wife told me that she was going to call me and warn me about how hot it was, but she thought I’d scoff and tell her I knew it was hot and that I’d be careful. I wish she had called, because I really had no idea and it would have at least prompted me to take water. She’s the more sensible one in this relationship.

I like to think that I continue to make stupid training decisions so that I can write about them here and tell others how to avoid doing the stupid things that I do. Today I was not smart, and I paid the price. It could have been worse – I probably would have had to walk the final mile if I hadn’t found the water fountain. I don’t think I’ve ever had full-blown heat exhaustion, but I may have come close today.

I’ll chalk this up as yet another reminder to me that I need to pay attention to the conditions outside as the weather continues to get warmer. A few weeks ago I flirted with dehydration, today it was over-exertion in the heat. Both made for pretty miserable runs.

So the take-home message here: Be smart, adjust your training schedule or run time if possible, and if you do decide to run when the heat is oppressive at least be smart enough to go really easy and bring some water.

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About Peter Larson

This post was authored by Peter Larson. Pete is a biology teacher, track/soccer coach, and dad (x3) with a passion for running, soccer, and science. If you'd like to learn a little bit more about who I am and what I do, click here, or visit


  1. Tom Davidson says:

    I picked up one of the smaller Nathan hand bottles (the 10oz one that fits in the palm) and I’ve used it twice this spring for runs just like you had today. It’s small enough not to be a burden on those <10mi runs. Might be worth checking out.

    • I’m usually pretty good about bringing a handheld or wearing my hydration pack on days like today, but was taken by surprise by the heat. Handhelds are great once you get used to them, and if you can build refill stops at parks into your longer runs they can help avoid the need to wear a pack. I have a Nathan Quickdraw handheld, but have not tried the smaller ones. Will have to check it out!

  2. Eman Coli says:

    I did a similar thing on Memorial Day, and brought water. Still got punched in the face by the heat. A long 14 became the worst 10 ever.

  3. Ruairidh says:

    Not wanting to be too annoying here, but I’d like to disagree with the overall message of your post. I think it’s very important once in a while to run well beyond what is one’s normal limits, to push oneself to a place that is so uncomfortable and painful it’s scary. As long as you’re not doing irreparable damage to yourself, which its sounds you haven’t, I think it’s a positive to remind yourself how hard it can, and should, be. Running shouldn’t be an easy sport and an unpleasant session does not equal a bad one. I don’t mean to launch a personal attack, it’s meant to be a more general comment, but your story just made me think that it can be taken for granted a wee bit.

    By the way, being from Aus I’m not sure how hot 81 in fahrenheit is or what it usually is over in the us of a.

    • Sure, you have to run in heat to acclimate which is why I do it, but pushing too hard in heat when not acclimated is not wise. There’s a difference between a hard workout and a hard workout in environmental conditions that could make it downright dangerous. My wife and kids wouldn’t appreciate a call from the hospital because I ran myself into heat stroke.

      I live in the Northeast US, very cold, snowy winters, hot summers but only for a few months. I ran a lot of runs in -10 Celsius or below this winter, and 88 converts to about 31 Celsius. The change is pretty rapid during May and June, and lack of acclimation causes me problems a few times each Spring when I forget that my body is not yet prepared to run in heat.

  4. Cody R. says:

    that’s why i keep it, on a hot day, either before 9 in the morning, or after 5 even stretching to 6 or 7 if it’s that bad

  5. The quote from your story sums up pretty well how our body deals with heat.”I was dying for some water, though I was still sweating plenty and did not feel dehydrated.” Your body was fine, just not use to the conditions. Have you read Waterlogged by Tim Noakes? Hydration has nothing to do with thermoregulation and the fastest runners are the most deyhdrated* at the end of a race.

    *Noakes has lots on what defines dehydration and heat exhaustion.

    • I need to read that book, but it’s a daunting one. I’ve spent the past 3 months working through the Game of Thrones books, now finished, so maybe onto some non-fiction :)

  6. I’ll be the next one to agree with Pete about being mindful of the conditions. This past Sunday I completed a fifteen mile trail run. The loop was 2.5 miles in length, and after 1-2 loops, I would refill my Nathan bottle (it holds roughly 22 ounces) at the water fountain and put another Nuun tab in for sodium and potassium.

    Though it’s early June, the humidity in Georgia, like other states in the Deep South, can be devastating if you aren’t acclimated. On the sixth loop, I felt like I was close to falling over from heat exhaustion, and it took me hours later in the day before I finally peed again. Heat, coupled with humidity, can wreck your run quickly. Run wisely.

  7. Seems like a world away from current conditions here in Scotland, it’s a “warm” day today at 15 degrees Celsius :-)

    I wonder if the bodies shock at finding unexpectedly hot conditions had a lot to do with your reaction as the conditions themselves.

    Could you central governor being upset by the your expectations of cooler conditions and prior runs in cooler conditions, compared the conditions that you encountered where your core body temperature rose quicker than expected?

    It’ll be interesting to see how you cope next time you got out in similar conditions, I suspect both physical and neurological adaptations will have started to take effect and you’ll have a much more mild reaction.

    Last summer I had a two week holiday in Spain and by the end of the holiday was able to do a tempo run in 35 degrees Celsius without undue stress. I never realised just how much I was sweating until I got indoors and out of the wind – suddenly I was drenched in sweat. It was really impressive to see how well I had adapted to the conditions. It took around 10 days to get really comfortable running in the hottest part of the day.

    • Opted for a hike today instead of a run since it was still pretty hot. Felt fine on the hike, but afterward a bit short of breath. Think I may need a day off tomorrow.

      • Why not try two short hikes/walks/runs rather than just one longer one. Give you body a chance to cool down in between and provide a nice double stimulus without any single bout of exercise being too stressful.

  8. Having run for 36 years in the furnace of Texas, I can tell you that the sun was more of a factor in your heat issues than the temperature. In July and Aug. here, it will be 92-95 degrees at 9 pm , but even those temps are comfortable with the sun down.

  9. Jacob Sconyers says:

    On my long run yesterday, I was also flirting with heat exhaustion. I’ve never before crashed and burned on a run like I did yesterday. I live in Boston, and I was out for a 16 mile run that would take me down the Neponset River, into the burbs, along a beach, then back home. When I started off, it was about 7:30am, sunny, and warm.

    The day started warming up very quickly, hitting about 85F and humid before long. I carry a Nathan waist pack with two 22oz water bottles, which is usually fine, though I plan runs to be able to top off my water as needed. Because my route followed a bike trail along the river, there was very little shade, and I was sweating profusely.

    About six miles in, there’s a park with a water fountain, and I took the opportunity to splash my face with cold water and top off my water bottles. I had probably consumed about 20oz at that point, but there’s no harm in keeping the bottles full. I would usually have another opportunity to top off my bottles at around mile 9, but the fountain was not on in that park. At that point, I had plenty of water, but was very hot along the exposed beach.

    After leaving the beach, I ran through some mild to moderate hills, and at about mile 12, I hit the wall like I never have before. My legs got heavy, and I started getting dizzy and sucking huge lungfuls of air. At one point, I looked down and my skin was very flushed and red. Even the palms of my hands were flaming red. I stopped and sat down in the shade of a building for several minutes until I could cool down slightly. It was scary.

    Over the last six miles or so, I stopped in the shade at least six times. I was almost out of water, so I was wringing sweat from my hat to help cool down my face and neck. I could maintain my pace while I was moving, but whenever the heat caught up with me, I got weak and dizzy and out of breath.

    As soon as my run was over, I drank a large bottle of water and a large iced coffee, totaling probably 50oz. This is on top of the approximately 60oz I drank while running. Drinking all those fluids at once at the end of the run was probably a mistake. I ate a small meal, took a cool shower, and then went grocery shopping with my wife. At the store, I got dizzy, very nauseous, and kind of short of breath. I chalk that up to hyponatremia, and it stopped after I had a fastfood burger and a couple of salt packets.

    For my body to have such an extreme response to what should not have been an extreme workout was scary. I’m going to pay more attention to the temperature in the future and start long runs earlier in the morning. I’m also going to pay more attention to salt intake when drinking a lot on a run.

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