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How the body handles exertional heat stress, and how you can manage it

May 31, 2017 by Spike Wimmer 2 Comments

Several issues ago, we discussed over hydration and the problems it can cause, and how to avoid it. With the heat of summer on the horizon, and endurance running events held at altitude and higher temperatures, we need to acclimatize our bodies before jumping from the frying pan into the fire. Winter temperatures will soon wane, and it would be good for your body to know how to prepare for an event where you expect it to be hot and dry throughout the race.

Since no two bodies and their metabolic requirements are alike, lets determine how much water we actually perspire and respire off during a workout or long run.

  • First we will need your bathroom scale. Weigh yourself naked prior to your run. Weigh your full water bottles that you will take with you on your run.
  • Run your complete work out, as hard as you would run in the event, try and keep the same pace.
  • Now weigh yourself again naked, note your weight – now weigh your water bottles again.
  • Determine what your weight loss was in respiration and perspiration, and take into account the weight of the water that you consumed.
  • Now you should have determined your personal rate of consumption of liquids over time or distance, or fluid expenditure.
  • This should give you a thumbnail estimate of whether you are hydrating enough or over hydrating, and how much water your body needs throughout the race.
  • For every pound that you lost, you need to replace 16 to 20 ounces of fluid and electrolytes to get back to where you started.

It is important that you sweat to cool your body’s core temperature. The areas that you will sweat the most, is the area that will cool your body off the quickest, so it is important that it is allowed to be exposed to evaporation as you run. Your back and your chest/torso will give up the most heat, and reduce your core temperature most effectively. In other words, wearing a hydration pack on a very hot race versus water bottles in each hand may hinder your body’s ability to give up heat and cool your core temperature. Secondary to your torso are your armpits, your groin and your neck, closest to your carotid artery.

***Using one of the new DPMR bandanas with ice and ice water will help tremendously in keeping your core temperature in check.

El Dorado creek sponge bath photo: Andrea Abel

How soon should I start pre-hydrating before a race?

Studies with ParaRescue Jumpers, deployed from cooler climates to say Afghanistan, determined that pre-hydrating 8 to 12 hours prior to deployment into an arid and or humid environment, was helpful in keeping their plasma volume adequate to stay ahead of dehydration.

Carbohydrates contain a higher amount of water than proteins, so the old carb loading adage, up to 3 days prior to an event will also help keep plasma volume optimal for starting your event in hot temperatures.

Without losing you further, I’ll stop here for now. If you have any questions that you would like a more in depth answer to, please don’t hesitate to message me. I could go on for hours as you can tell!

Best of luck to all of you trail animals this season…be safe, stay hydrated, and have fun!

 

~Spike

Filed Under: Fuel, General, Training

Reader Interactions

Comments

  1. Andy Pasternak says

    June 1, 2017 at 7:37 am

    Spike- I’m going to have to disagree with you slightly on this one but it’s mostly with the title and not the content. The data that pre-hydration or staying hydrated prevents heat related illness is pretty weak. You do need to listen to your thirst more as you do sweat more and fluid requirements do go up. However, most heat related illnesses are more related to intensity of exercise and wet bulb globe temp than hydration.

    Reply
    • Spike Wimmer says

      June 11, 2017 at 9:13 pm

      Yes, quite right Dr. Andy. I wrote the title, got short on time for deadline, and didn’t finish my complete thought. I completely agree that listening to your thirst is most important for individual requirements, and not listen to marketing strategies. Had I taken more time to write a complete article, it would have included heart rate monitoring in an arrid environment, say a sauna, at temps ~ 85°F…Taking 220 minus your age x (90-92%)= Target heart rate…perform for 10 minutes, increasing time each day by 10% for 7-10 days for heat acclimatization, and taking your wet bulb temp (humidity) into account as well. Also important, core temp must not exceed 107°F, but we are talking military extremes at this point. Thank you so much for reading my article, and giving valuable feedback. ~Spike

      Reply

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Keep an eye on Facebook for updates and cancellation due to weather.  Photo credit: Steve Woo These runs will depart from the Trout Creek Pocket Park, northwest corner of Bridge and Jiboom St (at the[...]
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5:30 pm Evening Speed-work with Martin @ Coldstream Canyon Truckee
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Evening Speed-work with Martin @ Coldstream Canyon Truckee
Join us for for Thursday evening speedwork for runner’s of all levels in Coldstream Canyon, Truckee. Run starts at 6pm.  Workout will be about an hour and can be adjusted to your level. Keep an[...]
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6:00 pm DPMR Weekly Social Run & Hangout... @ Trout Creek Pocket Park
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Oct 17 @ 6:00 pm – 7:15 pm
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Keep an eye on Facebook for updates and cancellation due to weather.  Photo credit: Steve Woo These runs will depart from the Trout Creek Pocket Park, northwest corner of Bridge and Jiboom St (at the[...]
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Who's psyched for the Pt Mariah Trail Marathon TOM Who's psyched for the Pt Mariah Trail Marathon TOMORROW?!! DPMR is so excited to bring you this second edition of the race that promises to be bigger and better than last year! RD Chris Cloyd and team have been working so hard all week with final prep. The course is in great shape with some beautiful fun flowy singletrack. He said he'd love a few more volunteers so checkout the signup genius on our volunteer page, but otherwise wants everyone to please come hang out, cheer, and join the party! 
Unique to this race is the 5 segment course that utilizes a central aid station and can be done as a 2 person or 5 person relay, in addition to challenging yourself to run the whole thing solo!
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Hey DPMRers!  We’ve got something special in th Hey DPMRers!  We’ve got something special in the works.  We’ve been collaborating with Alibi Ale Works to release a co-branded beer (YES!).   Join us for a social run next Tuesday, where we'll have the pleasure of running alongside Alibi's head brewer, Matt Garcia! We'll hit the trails together, and afterward, we'll gather at Alibi to brainstorm the perfect brew that represents our club.  And since the DPMR Pt. Mariah Trail Marathon is just around the corner, we're adding some extra fun to the mix. We'll also be assembling course markings during the event. It's going to be an unforgettable night! Hope to see you there!
🏃‍♀️🏃‍♂️ Calling All Running Ent 🏃‍♀️🏃‍♂️ Calling All Running Enthusiasts! Join Us in Supporting the DPMR Pt. Mariah Trail Marathon! 🏃‍♀️🏃‍♂️
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📅 Event Date: August 5th
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Sign up here for a volunteer shift today! Link in bio.
Thanks to everyone who came out and volunteered at Thanks to everyone who came out and volunteered at the Diamond Peak aid station this weekend at the Tahoe Rim Trail Endurance Runs.  Everyone out on the course really appreciated all of the support!!! Stay tuned, we will be posting the Volunt(hero) leaderboard soon!  In the meantime, we're seeking more incredible volunteers to join our team at the upcoming Pt. Mariah trail marathon, and we promise it'll be an experience you won't forget! 😄
Sign up today! No experience needed. Link in bio.
The heat is on! Our Volunt(hero) program is going The heat is on! Our Volunt(hero) program is going strong with more than 60 volunteers out helping runners get through our various aid stations this year. What is the Volunt(hero) program? The top 10 DPMR volunteers with the most hours logged in 2023 will be entered into a drawing for a chance to win free race entries for a year, up to $1000. We will be posting our leaderboard soon but only a few hours separate those at the top.  Adding a shift can catapult you in to one of the coveted top 10 spots to be included in the raffle.  So come and join us THIS WEEKEND out at TRT! There are still openings overnight, morning clean up Sunday, and sweeps for TRT (Double points for morning clean up).
All volunteers that work at least one 6 hour shift will be entered in to our lottery for a race entry in to the 2024 TRTER race. You get one entry for each 6 hour shift you work. Overnight shifts get a bonus with two entries! Winners of the lottery can choose the distance but 100 milers still must have a qualifying race.
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The Tahoe Rim Trail Endurance Runs are almost here The Tahoe Rim Trail Endurance Runs are almost here!!  Please consider volunteering with us.  We have many shifts available from Friday, July 14th through Sunday, July 16th! 
All volunteers that work at least one 6 hour shift will be entered in to our lottery for a race entry in to the 2024 TRTER race. You get one entry for each 6 hour shift you work. Overnight shifts get a bonus with two entries! Winners of the lottery can choose the distance but 100 milers still must have a qualifying race.
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Sign up here for a volunteer shift today! 🙏🏻
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