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This post could save your life.  Running a marathon might sound straightforward.  Keep running for 26.2 miles, and that’s all there is to it, right?  Wrong!  The physiology behind marathoning is complicated.  It is also serious.  Today we will cover an aspect of marathoning that directly impacts your safety.

Your body needs fluids and fuel to complete a marathon.  These also help ward off “the wall” (as we talked about in a previous post).  Now most peoples’ running energy (glycogen) store is depleted after about two hours of running.  Running out of “gas in your tank” obviously compromises your ability to keep running.  Furthermore, your body sweats out fluids faster than you are physically capable of drinking them in while running.  This is where it gets dangerous.  Both dehydration and over hydration are serious conditions.

Key takeaway:  You must refuel your body with ENERGY and FLUIDS during runs.

Now for my interpretation of the complicated science (in layman’s terms)…you sweat out more than water.  You sweat out minerals (or more specifically, electrolytes).  Those electrolytes include Sodium, Chloride, Potassium and Magnesium.  Maintaining a balanced ratio of these electrolytes and fluids helps your body properly function.  If you take in too much fluid and not enough electrolytes, your body becomes overhydrated.  Over hydration is very dangerous.

Key takeaway:  You must maintain an acceptable balance of fluids and minerals.  Do not OVER HYDRATE.

How much fluid you need in order to maintain hydration, but not overhydrate, is unique you and how much you sweat.  The experts recommend a broad guideline of drinking when you are thirsty, but NO MORE than 24 ounces (710 mL) of water or energy drink per hour.  Some runners go as far as taking the “sweat rate test“, weighing themselves pre/post run to estimate fluid loss.  I don’t go that far, but I do pay close attention to the quantity of fluids I take in.

Key takeaway:  Follow the recommended intake guidelines (14 – 24 oz. or 710 mL per hour) to maintain the proper hydration balance (ratio of electrolytes to fluids). You must have ACCESS to and MONITOR the AMOUNT of fluids you consume while running.

And what about fuel?  Fuel is no less complex!  Most runners can take in around 60g – 80g carbohydrates per hour (whereas they are burning up to 200g per hour). The ideal fuel contains easily absorbed carbohydrates (Sucrose, Glucose, Maltodextrin or a mixture of these).  Your fuel should also be quickly absorbable.  Studies show that fastest absorption happens when carbohydrates are 2%-8% of the ingredients.  Anything containing a higher amount of electrolytes (Sodium, Chloride, Potassium and Magnesium) is a bonus, as most energy drinks and carbohydrate gels contain very little.  Another nice to have is protein/amino acids, which can help increase endurance and minimize muscle damage.

Key takeaway:  You MUST refuel your body with easily and quickly absorbed carbohydrates (60g-80g per hour) during long runs.  If your fuel also has protein and electrolytes, that’s even better.

Summary:

Long answer to a short question.  Ideally, you would run with one source of fuel that addresses all of the above takeaways.  Unfortunately, there is no energy drink or running energy source does it all in terms of maintaining hydration balance and fueling your body.  I use a combination of water, energy drink and carbohydrate gels.  It hasn’t given me any trouble, but to be honest, it doesn’t meet all of the above criteria.

I will experiment and report back on alternatives in a future post.  In the meantime, use these takeaways to help determine a fuel and hydration strategy that works for you.   Here are some additional details on fuel options:

Options:

• Consistency (Energy drinks, gels, pastes, gums, bars, beans, powders, and the list goes on…)
• Flavors (ranging from gingerbread to vanilla)

What to look for:

•  Main carbohydrate source from Sucrose, Glucose, Maltodextrin or combination
• Carbohydrate concentration of 2-7% (hard to find)
• High level of electrolytes (hard to find)
• Protein/Amino acids
• Vitamins C and E (minimizes oxidative damage)
• Easy to carry (lightweight, doesn’t fall out) and consume while running
• Doesn’t upset your stomach (flavor, consistency)

Tips:

• I prefer gels for running because they are self-contained and easy to eat (squeeze like toothpaste).  They provide carbohydrates, protein and some electrolytes all in an easy to digest, frosting-like little nugget!
• Look for endurance/distance running formulations of energy drinks.  These are formulated to have higher amounts of electrolytes and lower concentration of carbohydrates than those in the grocery store.
• As a result of being formulated for higher concentration of carbohydrates and electrolytes, running energy products may taste stronger than what you are used to.  Consider diluting energy drinks a bit or consuming with a sip a water to help get them down.

How did I do?  I tried to give you the straight scoop without scaring you or overwhelming.  But fuel and hydration are more technical and serious aspects of marathon training.  If you learn nothing else from this series, PLEASE, remember that maintaining fuel and hydration is crucial.  Still have a question about energy for runners?  Post it on our Facebook site, and I’ll get you the answer.

Resources referenced in this post:

• Roberts, Bill, John Cianca, and Joseph Chorley. “Optimal Hydration: Establishing a Hydration Plan for Marathons.” American Medical Athletic Association: 1-2. American Road Race Medical Society. Web. 24 Apr. 2012.

• Noakes, Tim. “IMMDA Advisory Statement on Guidelines for Fluid Replacement During Marathon Training.” New Studies in Athletics: The IAAF Technical Quarterly 17.1 (2002): 17-24. Print.

• Rapoport, B.I. “Endurance Calculator.” Endurance Calculator. PLoS Computational Biology, Oct. 2010. Web. 25 Apr. 2012. <http://endurancecalculator.com/>.

• Fitzgerald, Matt. “Hydration and Nutrition During Running.” Runner’s World Performance Nutrition for Runners: How to Fuel Your Body for Stronger Workouts, Faster Recovery, and Your Best Race times Ever. [Emmaus, PA]: Rodale, 2006. 97-120. Print.

• Amy Jamieson-Petonic, R.D., manager of the Fairview Hospital Wellness Center in Cleveland. 

• Tucker PhD, Ross, and Jonathan Dugas PhD. “The Science of Sport: Sports Drinks, Sweat and Electrolytes.” Sports Drinks, Sweat and Electrolytes. The Science of Sport, 27 Nov. 2007. Web. 28 May 2012. <http://www.sportsscientists.com/2007/11/sports-drinks-sweat-and-electrolytes.html>.