I choose this subject because I love to coach, and especially, I like to coach football. In my country, football is played in the spring's and summer's months, and at this time hydration cause a lot of problems to the players because in summer the weather is really hot and humid (sometime 75% humidity). More importantly, this sport is not well organize jet, so coaches and players are really unresponsable in taking care of their water intake.

Hyperhydration

Definition: The practice of increasing the body-water stores by fluid consumption prior to an athletic event; a state of increased water content in the body (1).

In terms of survival, fluid replacement is the primary concern during prolonged exercise in the heat (3). The primary aim of fluid replacement is to maintain plasma volume so that circulation and sweating progress at optimal levels (1). Blood volume becomes reduced when sweating causes a fluid loss of about 2% of body mass (3). What is the best fluid for an exercising body? Surprisingly, cool water, especially in warm weather. It is best for two reasons, first because it rapidly leaves the digestive tract to enter the tissues where it is needed, and second because it cools the body (4). Superhydration can delay the effects of dehydration and help prolong endurance capacity. Hypohydration may increase heart rate and reduce plasma volume therefore stress will rise the core temperature in the cardiovascular system (1). Normal kidneys function very effectively to eliminate excess water during hyperhydration and conserve water during hypohydration (1). Wise athletes preparing for competition drink extra fluids in the few days of training before the event. The extra fluid is not stored in the body, but drinking extra fluids insures maximum tissue hydration at the start of the event (2). Must athletes who arrive even slightly dehydrated from chronic under-consumption of fluid arrives with a disadvantage (4). Two hours before exercise one needs to drink at least 3 cups of water (2). To better understand and measure the water intake, one cup of water is about 3 sips of water. After that, the athlete should hyperhydrate with about 16 ounces (or 400 to 600 mL.) of cold fluid at 40 to 50 F or 4.4 to 10 C about 10 to 20 minutes before exercising (1,3). Cold fluids are emptied from the stomach at a fast rate than fluids at body temperature (3). Fluid osmolarity must be taken in consideration because gastric emptying is slowed when the ingested fluid is concentrated with simple sugars, whether in the form of glucose, fructose, or sucrose. For example, a 40% sugar solution is emptied from the stomach at a rate only one-fifth that of plain water (3). When the weather is hot, drink water with only small amounts of glucose and electrolite, about 7% concentration (3, 10).

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Techniques to improve hypohydration during exercise:

Fluid volume is important because gastric emptying speeds up for each 100 mL increase in gastric volume up to 600 mL. Ingesting a volume of about 250 mL (8.5 oz.) every 15 minute is a realistic goal for fluid intake during exercise because larger volumes tend to produce feelings of a "full stomach" (3). This is about 1 liter per hour which could be enough to maintain fluid balance with mild to moderate sweating (1). It is really important re-hydrate during exercise because the thirst system is not activated until about 1 to 2 percent of body weight loss in dehydration (1). During exercise thirst becomes detectable only after fluid stores are depleted (2), so after exercise capacity is compromised. It is really important to understand that during periods of heavy sweating, it is very difficult to intake and to absorb enough fluids to replace all of the fluid lost. It is proved that can be lost 50 milliliters of fluid per minute, but only 20 to 30 milliliters per minute may be absorbed from the intestines (1). This is why hyperhydration and re-hydration are techniques that will help an athlete to not dehydrate ones' body in way to damage ones' performance and health. Also, it can be helpful to use sponging head and torso techniques. It is proved that using cold water in skin wetting techniques help reduce sweating so water lost. The benefits of this techniques are more prevalent in long endurance exercise (1), and they are more psychological rather than effective in decrease core body temperature. On the other hand, it also theorize that skin wetting in sports may be potential harmful. The psychological sense of relief may invite athletes to accelerate their pace increasing eat production without providing for control of the body temperature (1). If the core temperature increases, the risk of heat exhaustion may occur. It is important do not use cold water in skin wetting and especially do not poring water on the head or torso, but it will be better to use a sponge technique with water at room temperature so to decrease the body sweat and do not give false psychological informations to the brain. Another crucial factor is to pay close attention to water intoxication. Under normal conditions, a maximum of about 9.5 L (10 quarts) of water can be consumed daily without excessively straining the kidneys or diluting important chemicals. Consuming more than this volume can produce hyponatremia, or water intoxication, a condition related to significant dilution of the body's normal sodium concentration (3), and with a result in transient defect in renal diluting capability to excrete free water (7). In very hot environment decreasing the carbohydrate concentration promote gastric emptying of fluids. By maintaining a low osmolarity secretion is reduces, thus leading to a greater rate of net fluid absorption. Adding sodium and carbohydrate up to about 7% increases the net intestinal absorption rate. Increasing carbohydrate concentration above this level begins to have a deleterious effect on intestinal absorption of fluid. Sodium also promotes retention of ingested fluids and leads to an increased plasma volume response during re-hydration. In short, beverage composition to maximize fluid provision will not maximize carbohydrate availability (11). Also, after exercise water and 6% carbohydrate-electrolite beverage are better reabsorbed fluids (water 64 +/- 5% reabsorption: carbohydrate-electrolite 69 +/- 5% reabsorption: compare to caffeinated diet cola 54 +/- 5% absorption)(8).

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Hydration in cold weather:

Hypothermia, a below normal body temperature, or a loss of body heat, can pose a serious risk to our health (2). In cold weather the body still sweat, and body water is an excellent conductor for body heat. The hypothalamus is usually very effective in controlling the body temperature. If the skin receptors detect a colder temperature or the blood temperature is lowered, then the body will react to conserve heat or increase heat production(1). First, the blood will be shunted away from the skin to the central core part of the body. This decreases heat loss by radiation and helps keep the vital organs at the proper temperature. After that, shivering may be produce, which is the automatic contraction of muscles for extra heat (1). If the body continue to sweat there will be a decrease in blood volume and a decrease in internal temperature which it can cause damage to the vital organ that have to maintain a constant internal temperature (about 37 C). Fluid intake is really essential also in cold weather and the fluid should be warm or at room temperature (2). Dress in layers so clothing may be adjusted as body temperature changes (2-10). Muscular incoordination and mental confusion are early signs of hypothermia (1).

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Body adjustment in hypohydration:

Hypohydration effects physical performance because it lows the blood plasma. This is the main problem in losing water. Also, plasma osmolarity increase which is cause by the decrease of water in the extra-cellular plasma, the space between the cells. Sodium becomes more dense in the extra-cellular environment, so it pulls water from the intra-cellular plasma, inside the cell. As a result blood viscosity goes up; in other words, there is more chemicals, sodium and potassium, than water, and the central blood volume decrease. Because of that, the blood lose fluibility and the filling of the heart is more difficult, so there is a decrease in the filling of the heart which cause the heart to bit faster if it wants to pump the same amount of oxygen to the body tissue. Consequently, the stroke volume and the cardiac output decrease (9). Because of our body needs of sustain life, the blood concentrate more in replenish our organs, first. In consequence, the skin blood flow decrease so does the sweating mechanism. More importantly, the effect of this changes increase the core temperature which is the most important threat that leads to heat exhaustion (5). Symptoms of heat injuries are weakness, feeling of chills, goose pimples on the chest and upper arms, nausea, headache, faintness, disorientation, muscle cramping, and cessation of sweating (1).

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Is sport dehydration an advantage for certain sports?

Voluntary dehydration is often used by boxer, wrestlers, body builder, high jumper and volley ball players. There are many techniques to dehydrate our body; the most used are: exercise induce sweating which could be exercising in a hot environment with excessive clotting so to produce excessive sweat; or thermal induced sweating which could be taking a sauna; or diuretics (caffeine) to increase urine losses; or decreased intake of fluids and food; or a high protein diet based as a primary source of energy so that water is decreased because it is needed for the effect of the by-product urea excretion (1). A high percent of the wrestlers used dehydration techniques, sauna (51%), wrestling in a heated room (74%), wearing rubber or plastic suits while exercising (42%), restricting drinking (58%), laxatives (5%), and vomiting (11%). This are all hazardous practices (6). A major concern have been raised about dehydration among young athletes such as wrestlers and gymnasts. It seams that dehydration can delays growth and development during a period of active growth, can initiate eating disorders and short term effects including weakness, cold intolerance and lack of concentration (6). In a controversial study, hypohydration even up to a level of 8 percent of the body weight loss, will not effect physical performance factors in events involving brief, intense muscular effort (1). It could be a good way to perform better for high jumper and body builder (which I believe has to dehydrate more than 8 percent to be considerate in the winning competitors.) Another study have reported significant impairments in sports, with body weight losses of 4 percent or higher. An important factor is that anaerobic muscular endurance tasks lasting longer than 20-30 seconds have been impaired when subjects were hypohydrated. Suggested mechanisms of impairment include loss of potassium from the muscle and higher muscle temperatures during exercise (1). In aerobic endurance performance hypohydration of more than 2 percent of the body weight usually will lead to reduction in performance, The performance reduction is proportional to the degree of hypohydration, greater fluid losses leading to greater impairment (1). Hypohydration would significally decrease maximal aerobic power by 4-8 percent with a 3 percent weight loss during exercise, and this will be greater in hot environment (3).

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Ergogenic effect of glycerol in hyperhydration:

Adding glycerol to the water may be helpful to prevent dehydration and thermal injury(1). With experience in superhydration one may be able to tolerate larger amounts of water. An important thing to keep in mind is the diuretic effects that too much water can produce in the intestine, so if one tries to hyperhydrate, it is better that one practices first and not in the actual competition. Glycerol induced-hyperhydration was more effective than a water induced-hyperhydration to reduce the thermal stress of moderate exercise in the heat. The dosage was 1 gram of glycerol per Kg. of body weight along with 21.4 ml of water per Kg. (1). Glycerol may be used to increase body water stores prior to exercise in the heat and may regulate body temperature more effectively, which could provide ergogenic effects (1). Glycerol-induced hyperhydration was more effective than water-induced hyperhydration to reduce the thermal stress of moderate exercise in the heat. The result reported that the glycerol induced hyperhydration significally improved performance in a cycling endurance test to exhaustion at 65% of of VO2 max. During glycerol trial heart rate and rectal temperature were lowered and the plasma volume was increase. The finding was that glycerol induced a greater retention of fluids in the body than water hyperhydration. Glycerol helped to maintain the osmolarity of the blood, leading to better preservation of serum. It also lowered urinary output of water with better preservation of serum ADH level (5). The finding was that glycerol may be an effective ergogenic aid, particularly, for prolonged exercise under warm environmental conditions because of extra-fluid storage in the extra-cellular compartment (5). In conclusion, I can said that hydration is really important in sport performance and also in normal pleasurable exercise time. It can prevent illness and assure good health in players as well as in people who like to have a healthy exercise. Moreover, if hydration is not taken seriously during exercise as well as in normal life, it can produce risky health problems in all human being. As an ergogenic help hyperhydration with glycerol can improve the intake of water in the body by maintaining a better osmolarity in the extracellular environment, by lowering urinary output, and by reducing the thermal stress of exercise in hot weather so regulating temperature more effectively.

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References

1.- William, M. H. (1992). Nutrition for Fitness and Sport. Dubuque IA: Brown.

2.- Sizer, F., Whitney E. (1994). Nutrition: Concepts and Controversies. New York: West.

3.- Katch, F. I., McArdle W. D. (1993). Introduction to Nutrition Exercise and Health. Malvern, PA: Lea and Febiger.

4.- Hamilton E. N., Rolfes S. R., Whitney E. M. (1991). Understanding Nutrition. New York: West.

5.- William, M. H. (1995). Nutrition for Fitness and Sport. Dubuque IA: Brown.

6.- Berg, M. F. (1993). Obesity and Health. Hettinger ND: Health and Obesity.

7.- Putterman, C., Levy L., & Rubinger D. (1993). Transient exercise induced water intoxication and rhabdomyolysis. American Journal Kidney Dis., 21 (2) 206- 209.

8.- Gonzalez A. J., (1995). Rehydration after exercise with common beverages and water. Internal Journal of Sport Medicine, 13 (5). 399- 406.

9.- Heaps, C. L., Gonzalez A. J. & Coyle E. F. (1994). Hypohydration causes cardiovascular drift without reducing blood volume. Internal Journal of Sport Medicine, 15 (2). 74-79.

10.- Beeley, J. M., Smith D. J., & Oakley E. H. (1993). Environmental hazards and health. Medical Bulletin, 49 (2). 305- 330.

11.- Rehrer N. J. (1994). The maintenance of fluid balance during exercise. Internal Journal of Sport Medicine, 15 (3). 122- 127.

E-mail: Giorgio Volpi