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Dehydration

The importance of adequate bodily hydration cannot be overstated in its relation to proper physiological functioning.  The act of training takes this relationship a step further, in that hydration becomes absolutely invaluable to the conditioning of professional, amateur, and recreational athletes & bodybuilders who routinely engage in high-intensity and long-duration training.  Although the present accumulated wealth of information on this subject would immensely benefit this demographic, very little reliable and valid data trickles down to much of this population. 

At its core, the condition of dehydration amounts to nothing more than rudimentary arithmetic.  According to the Mayo Clinic, “Dehydration occurs when you lose more fluid than you take in and your body doesn't have enough water and other fluids to carry out its normal functions.”  It lists the ‘Common Causes’ of dehydration as intense bouts of diarrhea, vomiting, fever, or excessive sweating, and cites the inadequate intake of water during hot weather or exercise as traditional culprits for otherwise healthy people.  The clinic goes on to state that mild to moderate dehydration can usually be reversed by increasing the intake of fluids.  This is a clear and accurate depiction of what dehydration is on the surface, but like most athletes’ understanding of this concept, it too simplistically equates dehydration with mere water consumption and is therefore only part of a larger equation.

A better understanding of the other half of this equation can be gleaned from the inverse of dehydration, namely over/hyper-hydration and the phenomenon that best (and most extremely) illustrates this point is called Hyponatremia.  Better known as ‘Water Intoxication,’ Hyponatremia is a condition in which too much water is consumed too quickly.  This rapid, high-volume intake literally flushes valuable electrolytes and salts from the body at a faster rate than replenishing can occur, the result of which can be fatal.  The most recent publicly cited incident occurred on Friday, January 12, 2007.  Jennifer Strange, a 28-year-old mother of three, was found dead in her suburban Rancho Cordova, CA home hours after taking part in the “Hold Your Wee for a Wii” contest in which KDND 107.9 promised a Nintendo Wii video game system to the winner.  “A preliminary investigation [which was later confirmed] found evidence consistent with a water intoxication death,” said assistant Coroner Ed Smith.  The story can be found at:  http://www.msnbc.msn.com/id/16614865/.  So, regardless of whether not enough water or too much water is present, it’s evident that there is another factor involved in the regulation of hydration, namely that of sufficient electrolyte levels.

Much of what we know about the parameters of intense training and the resulting dehydration comes from animal studies.  Tufts University’s Cummings School of Veterinary Medicine studies on sport horse hydration are at the forefront of this research.  In one of their more prominent works entitled ‘Dehydration and Electrolyte Losses in the Sport Horse,’ the authors state: “You can lead a horse to water but you can't make him drink is a maxim that has long been used to underscore the apparent stubbornness of the horse.  In the heavily exercising, or heat-exhausted horse, however, this refusal to drink has nothing to do with personality or temperament, and everything to do with physiology…fluid and electrolyte composition…and the particular requirements of the equine athlete in work.”  Similarly, in human beings physiology takes precedence, and just as, if not more important to hydration than fluid consumption, is electrolyte level maintenance. 

At the most basic level, electrolytes are salts, such as table salt, that dissociate into separate ions when they are dissolved in water.  The most important electrolytes sodium (Na+), magnesium (Mg2+), potassium (K+), calcium (Ca2+) and chloride (Cl-) are integral to nerve and muscle function, as well as to almost every other physiological function in the body.  These electrolytes are distributed throughout the body in a highly ordered fashion, and disruption of said order can result in severe bodily dysfunction including heart and gastrointestinal problems, the inability to think clearly, and muscles cramps.  Fortunately, unless sickness occurs, humans typically only experience the latter, which is prevalent among poorly hydrated athletes.  Understanding why a horse won’t drink can help us better understand why drinking frequently and, more specifically, consuming electrolytes is so beneficial to the vigorously training athlete.

According to Tufts: “Your horse's body gets the signal that it is thirsty when one of two things happens: either the blood volume drops, or the sodium concentration in the extracellular fluid increases - that is, it gets concentrated, or salty.  Horses get the thirst signal more slowly than humans.  This is because in humans, Na+ is less concentrated in sweat, so sodium becomes more concentrated in the blood, and the thirst signal goes out quickly.  In horses, the sweat glands are very poor at conserving Na+ so even though the horse has lost a large amount of water and Na+, the signal does not go out for the horse to drink until a serious drop in blood volume occurs due to dehydration. Consequently, even though your horse is clearly dehydrated, when you lead him to water you can't make him drink!  He's not stubborn - his body is just not giving him an early enough warning signal.”  So, what lesson does the equine athlete teach the human one?  Basically, that one must pay attention to the body’s signals and replenish deficits of both fluid and electrolytes as readily and effectively as possible. 

The Gatorade name comes from The University of Florida football team, the “Gators.”  Gatorade Thirst Quencher was invented at The University of Florida to assist their athletes in combating the dehydration that limited their performance-hence “Gator…ade.” For more information on the origins of Gatorade, please visit the Gatorade Story Section.  In early summer of 1965, a University of Florida assistant coach sat down with a team of university physicians and asked them to determine why so many of his players were being affected by heat and heat related illnesses even though they drank plenty of water.

The researchers — Dr. Robert Cade, Dr. Dana Shires, Dr. H. James Free and D r. Alejandro de Quesada — soon discovered two key factors that were causing the Gator players to ‘wilt’: the fluids and electrolytes the players lost through sweat were not being replaced, and the large amounts of carbohydrates the players’ bodies used for energy were not being replenished.  The researchers then took their findings into the lab, and scientifically formulated a new, precisely balanced carbohydrate-electrolyte beverage that would adequately replace the key components lost by Gator players through sweating and exercise.  They called their concoction ‘Gatorade.’  Soon after the researchers introduced their Gatorade formula to the team, the Gators began winning… outlasting a number of heavily favored opponents in the withering heat.  In the years that followed, more and more NFL teams began placing Gatorade on the sidelines of their games and practices, and in 1983, Gatorade became the official sports drink of the NFL—a title it holds to this day.  Two decades after Dr. Cade and his team worked diligently to develop the optimum hydration formula that would become Gatorade.  In 1985 the Gatorade Sports Science Institute (GSSI) was founded in Barrington, IL, to conduct scientific research in the areas of exercise science, hydration, and sport nutrition.  Three years later, the lab would be expanded to provide advanced testing for athletes and new Gatorade products and flavors and develop education materials for sports health professionals around the world.  Gatorade is now also the official sports drink of the NBA, AVP, and PGA, Major League Baseball, Major League Soccer, and numerous other elite and professional organizations and teams.

The formula is primarily composed of 110mgs of sodium, 30mgs of potassium and 93 mgs of chloride.  As you can see this scientific blend consists of three of the five above mentioned electrolytes.  But, this unique drink also makes precise use of carbohydrates, another perspiration lost component, which promotes enhanced synergy.  Dr. Craig A. Horswill in ‘Is More Carbohydrates in a Sports Drink Better?’ noted that more is not better: “Research shows that optimal carbohydrate content for sports drinks is 6%. Gatorade is an example of a 6% carbohydrate beverage that is formulated with an amount of carbohydrate that helps stimulate fluid absorption.  Sports drinks with higher carbohydrate, content of 8% or more, slow fluid absorption.” 

The GSSI performs, among other things, in- depth studies on the subject of hydration with regard to athletes.  More specifically, they examine Hydration Research, Hydration and Performance, Dehydration and Rehydration, and Fluid Absorption/Gastric Emptying.  Edward E Coyle, Ph.D., in his work ‘Fluid and Carbohydrate Replacement During Exercise: How Much And Why?’ notes that: “Even a slight amount of dehydration causes physiological consequences.  For example, every liter (2.2 lbs) of water lost will cause heart rate to be elevated by about eight beats per minute, cardiac output to decline by 1 L/min, and core temperature to rise by 0.3o C when an individual participates in prolonged exercise in the heat.” 

Lastly, in ‘Sports Drinks: Myths and Facts’, Bob Murray, PhD, and Director of the GSSI addresses many of the falsehoods commonly associated with sports drinks which include:
Myth: Water is the best fluid replacement during activity.
Fact: While water is good, it has its limitations.
•    Water doesn’t have flavor to encourage drinking.1
•    Water turns off thirst before complete rehydration takes place.2
•    Water lacks electrolytes and carbohydrate energy that athletes need to perform at their best.3
Myth: Sports drinks are all the same.
Fact: The formula matters a lot. Research shows that:
•    Too high of a carbohydrate level slows fluid absorption.4
•    A blend of simple carbohydrates (i.e., sucrose, glucose and fructose), at an overall concentration that’s not too high, can help speed fluid absorption.5
•    Sodium content is important. Having enough sodium in the beverage will keep the thirst mechanism active for better drinking and will result in a more complete rehydration.6
•    Taste and flavor matter. If they’re not suitable for the exercise occasion you won’t consume enough to maintain proper hydration.7
Myth: Sports drink consumption during exercise contributes to weight gain.
Fact: According to research, exercisers who drink sports drinks during activity can work out longer and harder3,8 and are less likely to overeat following a workout.9 Research also shows that consuming carbohydrate during exercise makes activity feel easier.10 These are all positive benefits for those exercising to manage weight.

Myth: Sports drinks are high in sugar and calories.
Fact: Ounce for ounce, sports drinks have about half the calories and sugar of fruit juice or regular soft drinks. For example, Gatorade has only 50 calories and 14 grams carbohydrate per 8-oz serving versus fruit juice or regular soda, which have 100 to 110 calories and 27 grams of carbohydrate per 8 oz serving.
Myth: Sports-drink consumption triggers an exaggerated insulin response during exercise.
Fact: Actually, there is a modest insulin response to sports-drink consumption at rest or during exercise. Insulin release is a natural response to ingestion of carbohydrate-containing foods or beverages. High doses of simple carbohydrates (sugar) evoke the greatest insulin response. Comparatively speaking, sports drinks have low carbohydrate content and are often consumed during exercise, which blunts the insulin response. A slight rise in insulin following ingestion of a sports drink during exercise helps to increase the rate of glucose uptake and use by working muscles – a desirable effect to help boost performance.11,12
Myth: Sports drinks are only for events lasting more than 60 minutes.
Fact: Sports drinks provide benefits over water during vigorous exercise, even during bouts lasting less than 60 minutes. Research demonstrates that sports drinks help performance in endurance competitions as well as shorter-term events or stop-and-go sports, like football, basketball, soccer, tennis, and hockey.8,13
Myth: Sports drinks have too much salt.
Fact: Sodium is an important ingredient, but it doesn’t take a lot to make a sports drink work. For example, Gatorade contains enough sodium (110mg/8oz) for you to rehydrate, yet it is classified as a low-sodium beverage by the FDA. To put it in perspective, Gatorade has less sodium than an equivalent serving of milk or a slice of bread. Sodium is used in a sports drink because it activates thirst helping to ensure you drink until fully rehydrated.


REFERENCES
1. Passe, D.H. et al. Appetite 35:219-229, 2000.
2. Wilk, B. and Bar-Or, O. J Appl Physiol 80:1112-1117, 1996.
3. Below, P.R. et al. Med Sci Sports Exerc 27:200-210, 1995.
4. Ryan, A.J. et al. J Appl Physiol 84:1581-1588, 1998.
5. Shi, X. et al. Med Sci Sports Exerc 27: 1607-1615, 1995.
6. Wemple, R.D. et al. Int J Sports Nutr 7:104-116, 1997.
7. Passe, D.H. et al. Med Sci Sports Exerc 31:S322, 1999.
8. Davis, J.M. et al. Int J Sports Nutr 10:476-485, 2000
9. Melby, C.L. et al. FASEB J 15:A990, 2001.
10. Utter, A. et al. Int J Sports Nutr 7:274-285, 1997.
11. Febbraio, M.A. et al. J Appl Physiol 89:2220-2226, 2000.
12. Coyle, E.F. et al. J Appl Physiol 55:230-235, 1983.
13. Davis, J.M. et al. Int J Sports Nutr 7:261-273, 1997.
14. Mendoza, J.R., et al. Med Sci Sports Exerc 32:S238, 2000.

CITATIONS
Craig A. Horswill                                                                                                                            IS MORE CARBOHYDRATE IN A SPORTS DRINK BETTER?                                                                      Gatorade Sports Science Institute http://www.gssiweb.com/Article_Detail.aspx?articleid=436&level=2&topic=1
Edward E. Coyle, Ph.D.
FLUID AND CARBOHYDRATE REPLACEMENT DURING EXERCISE: HOW MUCH AND WHY? (1994)
SPORTS SCIENCE EXCHANGE
http://www.gssiweb.com/Article_Detail.aspx?articleid=23&level=2&topic=2

Bob Murray, PhD, FACSM
SPORTS DRINKS: MYTHS AND FACTS
Director, Gatorade Sports Science Institute

MayoClinic.com
‘Dehydration’
http://www.mayoclinic.com/health/dehydration/DS0056
Tuft University’s Cummings School of Veterinary Medicine http://www.tufts.edu/vet/sports/dehydration.html

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