Hydration for Athletes

Possibly the most under-emphasized aspect of sports nutrition, hydration can make or break an athlete’s performance. While fuel depletion during exercise can impair performance, inadequate water not only impairs exercise capacity, but can create life threatening disturbances in fluid balances and core temperature. With as little as 1% of body weight lost in fluid, athletes can experience thirst, fatigue, and weakness. (1) Thirst drives a person to drink, but it can actually lag behind the body’s need. When too much water is lost from the body and not replaced, dehydration develops. Dehydration refers to an imbalance in fluid dynamics when fluid intake does not replenish water lost. On the flip side, water intoxication occurs with excessive water intake or kidney disorders that can reduce urine output. In healthy individuals, dehydration is more common than water intoxication, but appropriate water balance is crucial to optimal performance and ultimately survival.

  • Water and Body Fluids

Water constitutes about 60 percent of an adults weight and it is the medium in which all life processes occur, including:* Carrying nutrients and waste products through the body* Maintaining the structure of large molecules* Acting as a solvent for minerals (i.e., sodium and potassium) and other small molecules* Acting as a lubricant and cushion* Maintaining blood volume* Helping the body regulate temperature.  Every cell in the body contains fluid specific for that cell called intracellular fluid, and around it is extracellular fluid. These fluids continually lose and replace their components, but the composition of each compartment remains remarkably constant. Because an imbalance can be devastating, the body continually adjusts water intake and excretion as needed. This type of balance is referred to as homeostasis. The body must excrete a minimum of about 500ml (about 2 cups) of water each day as urine to eliminate waste products that the body makes through metabolism. Above this amount, the body adjusts by excreting excesses to balance intake. In addition to water lost in the urine, the body also loses water from the lungs as vapor and the skin as sweat. The amount of fluid lost depends on the environment (heat and humidity), and physical conditions such as activity. On average, the body loses about 2.5 liter/day. Fluid maintains blood volume, which influences blood pressure. The homeostatic balance of fluids and solutes in the body is carefully regulated by the kidneys with assistance from several hormones including antidiuretic hormone (ADH) and aldosterone. The primary solutes that are involved in maintaining fluid balance are sodium, potassium, proteins, and glucose. Adequate intakes of water and electrolytes maintain hydration levels and regulate fluid shifts between the intra- and extra-cellular compartments. To maintain water balance, intake from liquids, foods, and metabolism must equal losses from the kidneys, skin, lungs, and GI tract.

  • The Needs of the Athlete

One of the primary functions of water for all individuals, especially athletes, is thermoregulation. A person can tolerate a drop in body temperature of 10 degrees (c), but an increase of only 5 degrees (c). Heat generated by active muscles can raise core temperature to levels that would incapacitate a person if caused by heat stress alone. (2)The body uses three mechanisms to dissipate heat:* circulation* evaporation* hormonal adjustment. The circulatory system works to deliver warm blood to the body’s shell. This produces the typical flushed face. Sweating begins within several seconds of the start of vigorous exercise and this evaporative cooling controls heat dissipation during exercise. Lastly, because sweat contains water and electrolytes, the body makes hormonal adjustments to help prevent the loss of salts and fluid. When the fluid lost in thermoregulation results in dehydration and a drop in blood volume, the end result produces circulatory failure and core temperature levels can increase to lethal levels.

  • Water Replacement

Total water intake at the reference level of 3.7 liters for adult men and 2.7 liters for adult women per day covers the expected needs of healthy, sedentary people in temperate climates. The obvious dietary sources of water are water itself and other beverages, but most foods contain some water as well. Most fruits and vegetables are almost 90% water, and many other foods like meats and cheese are approximately 50% water. The body also makes water during metabolism, when energy-yielding nutrients break down and their carbons, hydrogens, and oxygens combine to make carbon dioxide (CO2) and water (H2O).According to the Dietary Reference Intakes: The Essential Guide to Nutrient Requirements, published by the Institute of Medicine (3), most people get adequate fluids by drinking when they’re thirsty. However, the report does add that prolonged physical activity and heat exposure will increase water losses and therefore may raise daily fluid needs. Very active individuals, who are continually exposed to hot weather, often have daily total water needs of six liters or more. Both heat acclimatization as well as nutrition intervention is indicated for this population. According to the American College of Sports Medicine, general guidelines for fluid replacement are as follows: (5) Consume a nutritionally-balanced diet and drink adequate fluids during the 24-hr period before an event. Drink about 500 ml (about 17 ounces) of fluid about 2 hours before exercise to promote adequate hydration and allow time for excretion of excess ingested water.* During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating or consume the maximal amount that can be tolerated.* It is recommended that ingested fluids be cooler than ambient temperature [between 15 degrees and 22 degrees C (59 degrees and 72 degrees F])] to enhance palatability and promote fluid replacement.* Addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events of duration greater than 1 h since it does not significantly impair water delivery to the body and may enhance performance. Water loss by sweating peaks at about 3L per hour during intense exercise in heat. However, just about any degree of dehydration can impair performance. Adequate fluid replacement sustains the body’s potential for evaporative cooling. Rehydration protocols are often based on water lost as measured either by urine color, urine specific gravity, or changes in body weight.(4) If collecting urine is not feasible, sweat loss as reflected by weight loss can be used. An athlete’s pre and post workout (or event) weights are taken and whole body sweat rate can be calculated by dividing the sweat loss by the time period of collection. The following equation can be used to determine volume of fluid lost: (5) Sweat loss = (body weight before – body weight after) + amount of fluid intake – toilet loss. Alternatively, taking a simple measure of body weight each morning after emptying the bladder can show a pattern of hydration over time, provided gains or losses of fat and muscle tissue are not also taking place. Fluid balance, electrolyte homeostasis, cardiovascular function, and thermoregulatory control are intimately linked to fluid consumption and each has a major impact on health and performance. Fluid replacement helps maintain hydration and, therefore, promotes the health, safety, and optimal physical performance of individuals participating in regular physical activity. Athletes and their coaches should be aware of fluid replacement needs, and develop strategies and protocols to insure athletes drink enough to keep pace with sweat loss.


7 Common Factors of Successful Weight Management

Weight Management
These days, the topic of what’s in food is probably less important than what youYou’re working hard to lose the weight and get in shape. You bought a Beachbody® workout program. For some people, the results they’ve worked so hard for slowly disappear as bad habits return. Some wonder how “those thin people” can stay that way all the time.

In 1993, the National Weight Control Registry (NWCR) was founded to study the behaviors of “successful losers.” Those studied lost an average of 72 pounds, with a minimum weight loss of 30 pounds, and were able to keep the weight off for at least 5 years. Looking at various studies on obesity, the researchers found 7 common factors among those who were successful in maintaining their weight loss.

1. Eating a low-calorie, low-fat diet
Those studied ate an average of 1,385 calories per day (plus or minus 557), with an average of 26.6 percent coming from fat. Although 26.6 percent from fat may seem high to you, it is lower than the typical American’s diet, which consists of simple carbs and ready-to-eat, low-cost processed food. Also, the researchers found that fast food visits were limited to less than ONE per month (step away from the fries!).

2. Participating in a high level of physical activity
Those studied burned an average of over 2,600 calories per day. This calorie burn came from doing normal, everyday physical activity, including a lot of walking. In fact, over 75 percent of the participants included walking as a form of exercise, with 48 percent of the total participants adding walking to other forms of exercise. Think it can’t be done? The next time you go somewhere, try parking a little farther away and walking, take the stairs instead of the elevator, get off the bus or subway one stop sooner, or walk the dog around the block the next time you want to reach for a snack. It’s a great way to get in a little more exercise time.

3. Limiting TV viewing
I heard something great the other day. Someone said that they had always made excuses about not having enough time to exercise. Yet, they always fit in 3 hours of TV viewing every night. Instead of plopping down in front of the TV at night, try to find other things to do. Why not take this time to pop in your favorite exercise DVD? Take a walk with your kids, read a book, or take a class. Not only will it get you moving, it also stimulates your brain in a way that TV viewing can’t. It can also kill that urge for mindless snacking while watching TV.

4. Eating breakfast
Those studied rarely skipped breakfast. After “fasting” all night, your body actually needs the energy that a healthy breakfast can provide. Eating breakfast makes you less likely to grab that pastry in the kitchen at work or run out for fast food at lunchtime. It also keeps your metabolism going, so that your body doesn’t shift into the “protect and conserve all fat” mode.

5. Maintaining dietary consistency
To the successful weight losers (or winners!), “diet” is not a bad word. They are always consistent with how many calories they are eating. There is no “cheat” day or falling off of the wagon during holidays or vacations.

6. Maintaining a high level of dietary restraint
This goes along with factor #5. Those who are successful at weight loss are always conscious about the types of foods that go in their mouths. When you are trying to maintain your hard-deserved weight loss, be conscious of the types of foods you are eating. One hundred calories of your favorite candy treat are not the same as 100 calories of a protein shake. But, if you “mess up,” don’t beat yourself up. Those who are successful at keeping the weight off jump right back in where they left off, which leads us to the last common factor . . .

7. Frequent self-weighing
Seventy-five percent of those looked at by the NWCR weighed themselves at least once a week, with almost half (44 percent) weighing in every day. This allowed them to keep track of any weight gain (or loss) and to address it before it became a “big” problem. Also included in this self-monitoring behavior was the continued counting of calories and fat grams. This continued “reinforcement” goes a long way toward keeping you on track for a slimmer today and healthier tomorrow.