Drink water before, during, and after exercise to make sure you're getting enough.

Water is truly a performance enhancer. When a star U Conn basketball player took the advice of his sports nutritionist Nancy Rodriguez, RD, and started drinking enough to consistently void light-colored urine [what everyone should be aiming for], he was amazed at how much better he felt all day. Unfortunately, too many athletes overlook the power of this essential nutrient. Perhaps it’s your turn to give water a try? This article offers tips to enhance your water IQ, optimize your water balance, and help you feel and perform better.

•  You don’t have to drink plain water to get adequate water into your body. All fluids count, as do foods that have a high water content:

• Water is a major component of the cells in muscles and organs; about 60 percent of a young male’s body weight is water, as is about 50 percent of a young woman’s body weight.

• Water is essential for proper functioning of our metabolism, the biochemical reaction by which our bodies get energy. Your body simply cannot function without sufficient water, as noted by the fact that athletes die from dehydration. Your body also needs water to moisten food (saliva), digest food (gastric secretions), transport nutrients to and from cells (blood), discard waste (urine), and dissipate heat (sweat).

• Different body parts have different water content. For example, blood is approximately 93 percent water, muscle is about 73 percent water, and body fat is about 10 percent water. Water constantly moves between the inside and the outside of cells. In fact, about 4 to 10 percent of your body water gets replaced every day with “fresh” water.

Note: Bioelectrical impedance (BIA) methods of measuring body fat actually measure body water. From that, a formula estimates the ratio of water to muscle and fat. Hence, if you use a Tanita Scale or Omron device, be sure to maintain adequate hydration. If you’re dehydrated, you’ll end up with an inaccurate (higher) estimate of body fat.

Did you know? When muscles burn glycogen (long-term fuel), they release water to prevent dehydration—important during races.

• Your body produces about 8 to 16 oz. (250-500 ml) water per day during normal metabolic processes. During a marathon, a runner’s muscles can produce that much water over 2 to 3 hours. When muscles burn glycogen, they simultaneously release about 2.5 units water for each one unit of muscle glycogen; this helps protect against dehydration.

• Coffee is a popular source of water. Although once thought to have a diuretic effect, current research indicates coffee (in amounts normally consumed) hydrates as well as water over a 24-hour period. That is, after drinking coffee, you may urinate sooner, but you won’t urinate more than you consume. Army research on caffeine and dehydration confirms coffee (iced or hot) is an acceptable source of fluid for athletes, even during exercise in the heat. Hence, coffee and other caffeinated beverages such as tea or cola do count towards daily water intake.

• An increased concentration of particles in your blood triggers the sensation of thirst. If you’re a 150-pound athlete, you’ll start to feel thirsty once you’ve lost about 1.5 to 3 pounds of sweat (1 to 2 percent of your body weight).  You are seriously dehydrated when you have lost 5 percent of your body weight.

• Body water absorbs heat from the working muscles and sweat dissipates the heat, keeping you from overheating during exercise and in hot environments. The evaporation of a liter (about 36 ounces) of sweat from the skin represents a loss of about 580 calories.

• To determine how much water you lose when you sweat, weigh yourself (with little or no clothing) before and after an hour of hard exercise with no fluid intake. The change in body weight reflects sweat loss. A one-pound drop in weight equates to a loss of 16 ounces of sweat. A two-pound drop equates to 32 ounces—that’s one quart. Drink accordingly during your workouts to prevent that loss!

Body water absorbs heat from the muscles when you work out—and sweat dissipates that heat.

• When you sweat, you lose water from both inside and outside the cells. The water outside the cells is rich in sodium, an electrolyte that works in balance with potassium, an electrolyte inside the cells. Sweat contains about 7 times more sodium than potassium, hence sodium is the more important electrolyte to replace during extended exercise.

• Most athletes who lose more than 2 percent of their body weight  (3 lbs for a 150-pound athlete) lose both their mental edge and their ability to perform optimally in hot weather. Yet, during cold weather, you are less likely to experience reduced performance, even at 3 percent dehydration. Three to 5 percent dehydration does not seem to affect muscle strength or performance during short intense bouts of anaerobic exercise, such as weight lifting. But distance runners slow their pace by about 2 percent for each percent body weight lost by dehydration. Sweat loss of more than 10 percent body weight is life threatening.

• Adequate fluid intake can reduce problems with constipation and urinary tract infections. But, there is no research to back up theories that excessive (meaning more than the normal amount) water intake will improve weight loss, remove toxins, or improve skin tone.

• Best advice: drink in response to thirst. No scientific evidence supports the rule that you should drink eight glasses of water a day [although that's often a good rule of thumb to aim for], so you can simply drink in response to thirst. You can also monitor the volume of your urine. If your urine is scanty, dark, and smelly, you should drink more! If you have not urinated during your work or school day (8:00 a.m.- 3:00 p.m.), you are severely underhydrated.

While bottled water is more convenient, it may not be any better for you than plain old tap.

• Is bottled water better for you than tap water? Doubtful. According to the Center for Science in the Public Interest, nearly half of  bottled waters come from municipal water supplies—not from the mountain streams pictured on the labels. This suggests standard municipal tap water is high quality. Rather than spend money on bottled water, turn on your tap! This will help stop the flood of 95 million plastic water bottles that get discarded each day, of which only 20 percent get recycled. Drink plenty of water—but think “green.”

Copyright: Nancy Clark MS RD CSSD Feb 2012