Tips & Tricks: It’s Not Bonking, It’s Dehydration


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**Kinda scientific article, not meant to be medical advice, nor has it been reviewed by a doctor or other medical professional.  It is however, based on research of published articles in medical journals and other sports related articles linked below so you can look for yourself.**

Riding a bike has a lot of different dangers and obstacles, many of which are out of your control.  Whether biking across across town or taking on a double century, the first major obstacle your body will encounter is dehydration.

Dehydration peaks its ugly head in many different ways.  Among those are: dry mouth, reduced aerobic capacity, muscle cramps, decrease in sweating, eyes drying, reduced fine motor skills, decreased urine, lightheadedness, and eventually weakness, heart palpitations, nausea and vomiting.

I personally had a sever case of dehydration at a Half Ironman triathlon in the US Virgin Islands.  I got out of the water to start my next leg on the bike and my muscles just felt heavy. I could not get going and at first though it was the headwind.  Then I realized my power was gone and I just felt weak, and it just continued through the run and to the end of the race.  It was one of those days when most of the racers were not only done, but were also out of the transition area and clapped as I and the last 25 racers came to the finish line.  It was a very tough and humbling day.  But it was also a great lesson how dehydration affects your body.

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We’ve all experienced some degree of dehydration while exercising, but what’s really happening inside your body? Dehydration is the body’s loss of water such that it contains an insufficient volume of water for normal functioning.

The volume of water in your body is directly related to the volume of blood in your body.  As we all know, blood carries oxygen to your muscles to keep them functioning during aerobic exercise, but another core competency of your circulatory system is to maintain your core temperature (at ~37 degrees C) to help prevent overheating which can lead to coma through a process called thermoregulation.

Basically, the circulatory system performs thermoregulation by carrying heat away from your heart and other vital organs using heat transfer.  This type of heat transfer works by pumping blood through the organs and then to the skin.  The blood cells oxygenate the organs while the water in the blood cells absorbs the heat within the organs.  Water has a large heat capacitance (ability to store heat) and is the main part of the blood cell that assists in thermoregulation.  The “hot blood” is then sent to the skin to dissipate the heat through the skin surface.  This process regulates your core temperature.

The amount of blood flow to the skin during rest, or non-exercise periods is typically 4%.  This amount can increase to remove the excess heat from the core up to 48%!  This huge potential fluctuation in blood flow redirection is one of the main reasons maintaing blood volume, via hydration, is so important for cyclists and other endurance athletes.  Muscle tissue needs oxygen to produce power.  If your blood volume decreases, the amount of blood available to oxygenate your muscle tissue reduces, resulting in reduced ability to produce power.  (See Control of skin blood flow during exerciseMed Sci Sports Exerc. 1992 Mar;24(3):303-12; see also Major Functions of the Cardiovascular SystemHydration: Is your sports drink making you dehydrated?; and Skeletal Muscle Blood Flow).

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So the solution would be to replace that lost water by drinking a lot of water while working out, right?  Well, no, it’s not that simple.  Research has found water by itself does not work to rehydrate the body.  There’s an element missing in water, that element is sodium.  (See Sodium-free fluid ingestion decreases plasma sodium during exercise in the heatJ Appl Physiol 100: 1847–1851, 1999.)

So then just use a salt tab, right? Wrong.  Salt is sodium chloride (NaCl), what your body actually needs is Sodium Citrate (Na+).  While salt is ok in small doses, increased ingestion leads to gastrointestinal distress, which is neither helpful or fun during a long ride.  Sodium Citrate actually increases water retention resulting in greater hydration.  Hydration: Is your sports drink making you dehydrated?

So the question becomes, what can you drink that has the higher concentration of Na+?  A study at Drake University performed testing to determine the amount of sodium (Na+) was found in various sports drinks and other foods.  The sodium was either in the form of trisodium citrate or sodium bicarbonate, as both are effective in oral rehydration.  (See Citrate can effectively replace bicarbonate in oral rehydration salts for cholera and infantile diarrhea, Bull World Health Organ. 1986; 64(1): 145–150.)  The study looked mainly at sports drinks like Gatorade, Gatorade Endurance, Powerade and Accelerade.  (See Electrolyte (Na+, K+, Cl-) Concentrations in Assorted Sports Drinks and Milk).

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However, as the study was released in 2010, there are some newer kids on the block of rehydration for athletes.  They are Osmo, Nuun, Cytomax and DripDrop.

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Normalizing the results for the amount of Na+ in a 16 fluid ounce (~0.5 L) serving of each, here is the amount of Na+ in each of the major rehydration beverages:

 

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Gatorade: 8-11 (mmol/L)

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Powerade: 11.5 (mmol/L)

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DripDrop: 30 (mmol/L)

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Accelerade: 63.5 (mmol/L)

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Gatorade Endurance: 105.5 (mmol/L)

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Cytomax: 180 (mmol/L)

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Nuun: 360 (mmol/L)

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Osmo: 360 (mmol/L)

There’s more to replacing the fluids lost in your body than just the Na+ content, but good rehydration starts there.

We have both had success with Osmo, Nuun and DripDrop, although we have done our best using Osmo on the ride and Nuun as a pre-ride hydration aide. Since my experience in the USVI, I revamped my hydration by adding two more bottles to my bike and starting to us Osmo as my hydration supplement.   Less than a month after my experience at the Half Ironman in the USVI, I competed in the Escape from Alcatraz and had one of my best races ever!  I am a firm believer in the value of hydration.

Get out there, try out the rehydration beverages that look best to you and good luck on your next ride!!!

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