Recommendations for Hydration
TYPES OF SPORTS DRINKS
Fluid Replacers
Examples: Water, Gatorade, 10K, Quickick, Max
These drinks are absorbed as quickly as water and typically are used for activities lasting less than 2 hours.
Carbohydrate Loaders
Examples: Gaterlode, Exceed High, Carboplex
These drinks replace more muscle glycogen to enhance greater endurance.
They should be used after ultra-endurance events to increase muscle glycogen resynthesis after exercise.
Nutrition Supplements
Examples: Gatorpro, Exceed Sports, Ultra Energy
These supplements are fortified with vitamins and minerals and they help athletes maintain a balanced diet.
They can be used as a meal replacement supplement for athletes who wish to skip a high fat meal, or as extra calories for athletes who wish to gain weight.
WHAT NOT TO DRINK
Drinks with Carbohydrate (CHO) concentrations of greater than eight percent should be avoided.
Fruit juices, CHO gels, sodas, and sports drinks that have a CHO greater than six to eight percent are not recommended during exercise as sole beverages.
Beverages containing caffeine, alcohol, and carbonation are not to be used because of the high risk of dehydration associated with excess urine production, or decreased voluntary fluid intake.
HYDRATION TIPS AND FLUID GUIDELINES
Drink according to a schedule based on individual fluid needs.
Drink before, during and after practices and games.
Drink 17-20 ounces of water or sports drinks with six to eight percent CHO, two to three hours before exercise.
Drink another 7-10 ounces of water or sport drink 10 to 20 minutes before exercise.
Drink early - By the time you're thirsty, you're already dehydrated.
In general, every 10-20 minutes drink at least 7-10 ounces of water or sports drink to maintain hydration, and remember to drink beyond your thirst.
Drink fluids based on the amount of sweat and urine loss.
Within two hours, drink enough to replace any weight loss from exercise.
Drink approximately 20-24 ounces of sports drink per pound of weight loss.
Dehydration usually occurs with a weight loss of two percent of body weight or more.
WHAT TO DRINK DURING EXERCISE
If exercise lasts more than 45-50 minutes or is intense, a sports drink should be provided during the session.
The carbohydrate concentration in the ideal fluid replacement solution should be in the range of six to eight percent CHO.
During events when a high rate of fluid intake is necessary to sustain hydration, sports drinks with less than seven percent CHO should be used to optimize fluid delivery. These sports drinks have a faster gastric emptying rate and thus aid in hydration.
Sports drinks with a CHO content of 10 percent have a slow gastric emptying rate and contribute to dehydration and should be avoided during exercise.
Fluids with salt (sodium chloride) are beneficial to increasing thirst and voluntary fluid intake as well as offsetting the amount of fluid lost with sweat.
Salt should never be added to drinks, and salt tablets should be avoided.
Cool beverages at temperatures between 50 to 59 degrees Fahrenheit are recommended for best results with fluid replacement.
FLUIDS & HYDRATION
Hyponatremia and Dehydration
Dehydration
During exercise sweat and water vapor from increased respiration cause a reduction in body fluid. The rate at which this occurs depends on climatic conditions, exercise intensity, and individual fitness and acclimatization. This is variable from person to person. It is most easily measured by weight lost during exercise. The role of sweating during exercise is heat dissipation. As sweat evaporates from the body it cools the surface of the skin which in turn cools the body. Radiant heat obstructs this process as do dark colored clothing and non-breathable fabrics. Wind expedites heat dissipation. That is why cyclists have fewer problems with over heating. However, they need to be aware that they are losing fluid just the same and will need to replace lost fluid and electrolytes as well.
Exercise studies have shown that dehydration, or inadequate fluid intake, can lead to diminished performance and premature exhaustion. Weight loss of 3% or greater has been shown to result in reduced performance levels. The most serious effect of dehydration is impaired heat dissipation, which can elevate body core temperature to dangerously high levels, resulting in heat exhaustion and potentially fatal heat stroke.
The symptoms of heat exhaustion include: cool, moist, and clammy skin, heavy sweating, low blood pressure, high pulse, dilated pupils, headache, nausea / vomiting, giddiness, confusion, decreased urine production, and collapse. It may actually develop over several days. Symptoms for heat stroke may include a lack of sweating, confusion, weakness, dizziness, rapid breathing, convulsions and coma. It too may develop over days. Treatment for both includes rapid cooling and rehydration and emergency care as soon as possible.
The goals of hydration during exercise are to maintain adequate fluid and electrolyte levels to maintain optimal performance and to help the body dissipate heat during exercise.
To prevent heat related conditions from occurring:
1. Stay hydrated. Thirst is not a good indicator of fluid balance.
2. Drink about two cups (500ml) of fluid 2-3 hours before exercise. Continue to drink approximately 3-5 oz of fluid every 20 minutes of exercise.
3. After exercise fluid and electrolyte replacement remain important issues. Changes in body weight are more accurate in gauging how much fluid you lost and how much fluid needs to be replaced.
4. Weigh yourself prior to workouts. At the end of the workouts, weigh your self after toweling off the sweat. The weight loss in ounces represents the fluid volume in ounces to be replaced.
6. For activities lasting over one hour, beverages containing 6-8% carbohydrate and electrolytes are recommended for hydration in addition to water. Prolonged exposure to heat, humidity and sunlight can lead to accumulated losses of electrolytes as well as fluid.
The following conditions may increase your risk for heat illness:
obesity, low fitness level, lack of heat acclimatization, sleep deprivation, use of diuretics or antidepressants; or a recent illness with fever, diarrhea, or respiratory symptoms.
Hyponatremia
Previously thought to be a rare condition associated with chronic illness, hyponatremia has become much more frequently diagnosed in endurance athletes. Hyponatremia (low blood sodium) can result from drinking too much water during prolonged exercise (greater than 4 hours). Sodium is lost from the body through sweating. When training in hot humid environments and /or when exercising for long periods of time, sodium replacement is as crucial as fluid replacement before, during, and after endurance activity. Avoid drinking excessive amounts of water and fluids in general. If water alone is used as a replacement drink, sodium deficits would actually increase. Electrolyte replacement is better than water; but, it may still cause over-hydration if used to excess during prolonged and strenuous exercise. Nonetheless, sodium replacement is important. This is especially true in people
who sweat excessively.
Hyponatremia can present with such symptoms as nausea and vomiting, weakness, in coordination, severe headaches, puffiness, disorientation and confusion. Difficulty breathing, seizures, and even death may occur as well. This condition often occurs a few hours AFTER endurance activity ceases.
For the last twenty years it has been diagnosed in ironman distance triathletes and ultra marathoners. More recently, it has been diagnosed in marathoners. It is more prevalent in hot, humid climates. It occurs almost exclusively in slower marathoners, typically finishers beyond 41/2 hours. The cause of this condition is over-hydration. This may be in response to fears about the heat and dehydration. It may occur in slower runners because they are on the course longer and are likely to drink more frequently and to drink greater volumes per water stop. As marathons have become more popular with first time and novice runners, problems associated with hydration and especially hyponatremia have increased.
Hyponatremia is a very serious and life threatening condition. Dehydration rarely is. It is vitally important that runners understand the dangers of drinking too much and the relative danger of drinking too little. The adage of drinking until your urine is clear is misguided and inappropriate. Urine should remain light yellow and volume should normal. Dark urine is an indication of dehydration or blood in the urine (if pink or red). However to extrapolate that clear urine is better is incorrect.
Preliminary data indicates that women may be more prone to hyponatremia than men. This may be hormonally based. It may also be somewhat behaviorally based as women tend to drink more than men; however, they are smaller and therefore would need less fluid volume than a man to replace fluid lost during exercise.
There has not been any clear association of NSAIDs (Advil, Motrin, Aleve) with the incidence of hyponatremia. However, it is not wise to use these medications in large doses without a physician's advice.
To PREVENT this serious and potentially fatal condition from occurring:
1. In hot and humid conditions or when exercising over one hour, replenish fluid loss with beverages containing electrolytes. Water alone is ineffective as it can reduce the stimulus to drink as well as cause increases in urine production (and, greater fluid loss). Drink small amounts of fluid (3-5oz) every 20 minutes.
2. Drinking fluids with carbohydrates can be a more effective form of re-hydration. Carbohydrates can be beneficial as fuel replacement as well, thus enhancing performance. However, carbohydrates will slow down absorption of water. As the concentration of carbohydrate increases, the absorption rate of the fluid decreases. High carbohydrate concentrations (>10%) will actually cause fluid to be pulled back into the gut, worsening dehydration. Most commercially available carbohydrate drinks are 3-6% carbohydrate.
3. Salt your foods. Ingesting excess sodium is rarely a problem if volume intake is sufficient and kidney function unimpaired. However, salt tablets are not recommended as the amount of sodium is so great that it will cause fluid to enter the gut, causing nausea and vomiting. This will worsen hydration problem.
4. Determine individual rates of fluid loss by weighing yourself before and after a run after toweling off the sweat. The weight loss in ounces represents the fluid volume in ounces to be replaced. This is the most accurate way to prevent over and under hydration during and after long runs and races.
5. If you are going to be exercising for more than four hours, try experimenting with salty snacks (i.e. pretzels, saltines) when you get hungry during the run.
6. Avoid using pain relievers and anti-inflammatory medications during endurance activity.
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