Starting the ‘Running in Heat’ Round Table Discussion

One of the topics that takes up constant brain real estate with runner’s this time of year is, how to successfully run thru the summer months.  You may have even already noticed lot’s of health and fitness articles or running articles specifically tipping you off on the best products out there to help you run or exercise thru the summer months.  I want to take more of a subsurface look, within this post and the next several I”ll be posting, about the specific things runners have to manage in their lifestyles 24/7 in order to be able to get thru a run safely, prepare for the next run and recover from the previous run.  My inner science geek loves understanding and learning about how we are physiologically affected by things like heat, dehydration, sodium loss, and an imbalance in minerals in our body due to excessive sweating.  Today’s blog post though is dedicated to Starting the ‘Running in Heat’ Round Table Discussion.

Common Terminologies

So, before we jump off into the deep end of the Running in Heat hot topic (haha, no pun intended…well ok, maybe somewhat intended;)) I want to just cover a few basics today.

Some common terminologies that you may come across when you read or hear information regarding dehydration are hyponatremia, thermoregulation, and heat acclimatization.   I also want to briefly just introduce a concept called “carbohydrate depletion/loading” and tell you why debatably it can be deemed as an unsafe regimen if you’re running in the heat and humidity but may have to save this slightly lengthier topic for the next blog post.  First things first,…terminology.

What is Thermoregulation?

In a nutshell, thermoregulation is our bodies abilities to maintain an internal body temperature despite the external surrounding temperature.  A few weeks back I wrote a blog post called How Being “Soft” and Teeth Chattering Have Real Effects on Running Performance”.  In my post, I talked about how the cold and rainy weather conditions affected runners and may have been the cause to an early “bonk” on marathon day for runners during this last Boston Marathon.   Even pro athletes were unable to physically find a homeostasis thru the harsh high-calorie burning race day weather.  This concept stepping on the fringe of hypothermia effects. Today’s post on thermoregulation in hot and humid conditions is similar, yet on the opposite end of the Fahrenheit gauge, and addresses hyperthermia

When your body is overheating, it’s cooling mechanism is to sweat which also contributes to a runner’s ability to thermoregulate.  This is of course at the expense of any stored body fluids.  Jack Daniels, Ph.D. schools us in his book ‘Daniel’s Running Formula‘, “when a loss of fluid causes body weight to drop 3-5%, adverse effects on performance will occur.” 

Concurring exercise scientist, Robert Murray quotes;

“If sweat loss is not replaced during exercise,” says Robert Murray, PhD, an exercise scientist who serves as a consultant for the Quaker Oats Company, “the resulting dehydration compromises cardiovascular and thermoregulatory function, increases the risk of heat illness, and impairs exercise performance.”

The “Science of Sweat”

You may also like to read one of the dedicated chapters in the book ‘Marathon’ by Hal Higdon, called “Drinking on the Run”.  The book breaks down the “Science of Sweat”  and gives us science geeks more insight into the relationship between dehydration and blood volume.

If you choose to read, you’ll learn a little bit about one of three roles in preventing muscle cramps when running long distances or running in hot and humid weather.  Higdon quotes and elaborates from several sources.  The first, Nancy Clark, RD, director of nutrition services for SportsMedicine Brookline in Boston and author of Nancy Clark’s Sports Nutrition Guidebook  says, “the three roots of heat cramping are salt loss, dehydration, and muscle fatigue” 

Secondly, he quotes Dr. Eichner, MD, of the University of Oklahoma Medical Center and a member of the Runner’s World Science Advisory Board.

“Sodium is key, not only to maintain blood volume but also to help nerves fire and muscles work.  Sodium depletion short-circuits the coordination of nerves and muscles as muscles contract and relax.” – Dr Eichner

According to Dr. Eichner in Higdon’s book, he suggests that sodium depletion can be one cause of muscle cramping.  He proceeds to advise a few strategies like, ample long runs within your training to build muscle endurance, and a balanced diet with fruits and vegetables which of course contain necessary vitamins and minerals like sodium, potassium, magnesium and calcium.  He also recommends alternating fluid intake between water or a sports drink, at fluid stations during a marathon.  Amongst a couple of other cramp preventing strategies he caps off his advice by suggesting that runners learn their sweat rates by weighing themselves naked before and after a 1-hour run.

He gives this ratio, “losing 1  pound equates to losing 16 ounces of sweat”.  For me, this may be an aggressive measure of action but if you are one that would consider yourself an extreme sweater or only have the option to run after work in the hot late afternoon or early evening summer, then this may be more of a reality for your proactive running self.

You can read up and find more specific ways to calculate and test your fluid loss in Daniel’s Running Formula book, which includes Worksheets for Calculating Fluid Loss and Determining Fluid Needs.

Acclimatizing to Heat

Scientists have discovered that the runner’s body will eventually acclimatize to heat after a couple of weeks of training in these conditions.  In fact, your heat tolerance can allegedly increase by 50 percent by conditioning according to one of Iowa’s very own exercise physiologists at the University of Iowa, Carl Gisolfi, Ph.D.   And according to previously mentioned Dr. Murr,ay we will expand our blood volume.

Through the process of acclimatization, we can even train our bodies to become more efficient sweaters and the sweat glands being to learn to conserve sodium.  Don’t forget this is our bodies defense mechanism in the form of condensation and cooling the hot engine within.

Main lesson here is not to wait until race day to perform a litmus test on your body’s ability to effectively function.  If you are able to train during a cooler time of day (morning or evening) to ease into the acclimatization process than do so.  Also, it’s pretty easy to snag up non-porous or ‘sweat wicking’ materials now that help keep heavy fabrics acting like “sweat blankets” off of the skin.  If you’re going to wear a hat for sun protection off of your face, try placing a wet sponge or even a dollar bin gel ice pack tucked underneath.

Of course, there are also a myriad of other hydration paraphernalia products out there to run with such as Camelbak hydration backpacks, Nathan hydration belts, etc.  I have both of these and use them not just for fluid but to keep cell phone in tow for the “just in case” scenarios.

Obviously, you’ll also want to make sure you’re drinking prior to running.  My simple advice here is if you’re an early bird runner (time of day when it’s actually the most humid) then start your hydration and fluids the 24 hours prior.  Don’t overestimate your ability when it comes to running in the heat!  Be conservative to start off and perhaps choose a route that loops past home instead of an out and back.  Or at the very least runs past a few splash pads or parks with drinking fountains along the way.  Know that the process of acclimatization may take 7-14 days and that you should plan to slowly progress any training into hotter temps.

You may also balance the hydration efforts with some slightly salty snacks like tortilla chips and guacamole (bonus two-fer for the healthy fat), pita chips and cottage cheese (bonus carb to protein ratio), or some sweet and salty trail mix.


I saved this term for last because after putting such a heavy emphasis and focus on dehydration and the safeguards in relation to running in heat and humidity, a concept like hyponatremia almost seems somewhat contradictory.   But does it?…

During the summer months the risk of dehydration, of course, has you constantly thinking about drinking as much as possible thru out your day.  And back in the day, you used to hear the advice of drinking 8 glasses of water a day.  However, can the same advice apply to two drastically different sized human beings?  I mean, if our adult bodies are made up of something like 60% water doesn’t it stand to reason then that someone like Shaquille O’Neal would have more of a percentage of a hydration requirement versus someone my size which is 5’3″ and somewhere around 105lbs?

I like the more scientific approach and advice of drinking half your body weight in ounces a day.  Simple math = simple hydration recipe.

So, with that being said and a realization being made in correlation to the ratio of our body mass vs water, we can take another step towards concluding that even further on the scale of hydration there is a risk of over-hydrating.  Now, over-hydrating is not necessarily a word or scientific concept but the point I’m getting at is the definition and extreme case of hyponatremia.

“Hyponatremia means low blood sodium.  Excessive fluid consumption lowers the concentration of sodium in the blood.” -Amby Burfoot, ‘The Thinking on Drinking’ (pg. 288, Marathon The Ultimate Training Guide).

You rarely hear of these instances but they are still a real cause for concern, especially if you’re running long distances of a half or full marathon.  Amby Burfoot shares the analogy in Higdon’s book of marathon runners who sip from their water bottles the entire day before a big race, while they’re meandering around the health expos and such, and then consume water at every aid station during the first 4-5 hours of a marathon.  It quickly gives you a visual of the sodium in the blood being diluted and sodium concentrations then becoming too low.

How Does a Carbohydrate Depletion/Loading Regimen Affect Dehydration?

Here is a quick synapse in my own layman’s terms and according to what I’ve gathered or understood from articles and books out there of what carbohydrate depleting/loading regimens are and why endurance athletes sometimes implement this regime as part of their training strategy.

Without getting too in-depth on the dietary strategies of a carbohydrate depletion/loading regimen (and because I’m not a professional dietician), what I can tell you is that it is basically a strategy that stemmed from scientists discovering that endurance capacities and race performances being enhanced after heavy carbohydrate consumption.

Scientists say that our muscles store carbohydrates in the energy form of glycogen and distance or endurance runners and athletes have shown stronger or faster performance by loading these energy stores prior to a race performance.  The philosophy is that if endurance runners limit carbohydrate intake and deprive the muscles of their glycogen, then essentially they’ll learn to perform from a depleted state.  Then just prior to an athlete partaking in their chosen endurance event they load the muscle stores and body with a high carbohydrate intake and then the glycogen “starved” muscles hoard, for lack of better terms, the glycogen and the equation comes full circle.

What does this have to do with dehydration?  Well, it’s the glycogen in our muscles that helps store water within our bodies.  So, very blatantly put, if there’s low glycogen that means there’s less water content in our bodies.  A simple analogy is the no-carb diets and the body shedding instant pounds by loss of water weight.  So, you can quickly see the correlation between potential dehydration and carbohydrate depletion.

*Let me add here that I am NOT a doctor, or licensed dietician, and would encourage you to do your own research on this topic and the relationship to distance running to make your own conclusions.

Tricks to Keep Your Hydration Game Strong

Okay, so now are you thoroughly confused on whether to hydrate or how to hydrate?  I hope not and I hope that what you have gained was at least a better understanding of some of the terminology surrounding the hydration game topic and how to beat the heat as a runner.

No one recipe for hydration should be considered a fail-safe prescription for all!  Practice and experiment safely with what works or doesn’t work for you.  I will share what’s worked for me, or tips I’ve read about that I can share.

  1.  Run during the coolest parts of the day – early morning or late evening when the sun is not at it’s peak.
  2. Choose a shady route – preferably one that offers opportunities to hydrate along the way.  Concrete and asphalt are going to retain heat from the sun more than grass or a pea gravel trail
  3. Look at your weather app and try to choose running into the wind on the return route home, which will be on the latter half of your run or core temperature having already risen from the first half of your run.
  4. Wear loose or light fitting clothing that offers sweat wicking properties.  Or if you’re comfortable with running shirtless (men) or in just a sports bra (women) then go for it.
  5. A hat with a brim can actually trap heat being emitted from the head but you could soak it in cold water before heading out to keep yourself cool along the way.
  6. Don’t wear black or dark colored clothing if the sun is still up.  Wear light colors to reflect the sun.
  7. Drink on the run and learn how, when, and what your body likes best to drink.  Consider investing in a hydration belt, or the like, of some kind.
  8. Take advantage of front yard sprinkers or splash pads at parks to run thru.  The cool water will help you keep cool and lend a cooling effect on the surface of the skin.
  9. Err on the side of caution and run slower or shorter distances until you become more acclimatized.
  10. Let family or loved ones know your common running routes and take a cell phone as back up

Run safe, run smart!!