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Water Enhances Sports Performance

Looking for ways to help your child perform better at sports? Try drinking more water

Drinking more water is a wonderful way to achieve peak performance in sports. When a star U Conn basketball player took the advice of his sports nutritionist Nancy Rodriguez, RD and started drinking enough to consistently void a light-colored urine, 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 child's turn to give water a try? Here are some "droplets" of information to enhance your water IQ, optimize water balance, and help your child feel & perform better in sports:

  • It's a myth that only plain water works for hydration. All fluids count, as do foods that have a high water content, including food such as
    • oatmeal (84% water);
    • low fat milk (90% water);
    • coffee (99.5% water);
    • lettuce (96% water);
    • tomato (95% water);
    • broccoli (89% water);
    • low fat vanilla yogurt (79% water); and
    • ice cream (60% water).
  • Water is the solvent for biochemical reactions. The human body cannot function without sufficient water, which is why athletes can die from dehydration.
  • Your body needs water for a variety of reasons, including to:
    • moisten food (saliva)
    • digest food (gastric secretions)Basketball player drinking from water bottle
    • transport nutrients to and from cells (blood)
    • eliminate waste (urine), and
    • dissipate heat (sweat). 
  • Water is a major component of the cells in muscles and organs:
    • about 60% of a young male's body weight is water
    • about 50% of a young woman's body weight.
  • Different body parts have different water contents:
    • blood is approximately 93% water
    • muscle is about 73% water, and
    • body fat is about 10% 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 are dehydrated, you'll end up with an inaccurate (higher) estimate of body fatness.

  • Water constantly moves between the inside and the outside of cells. About 4% to 10% of body water gets replaced every day with "fresh" water.
  • The human body produces between 8 and 16 ounces (250-500 ml) of 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 will not urinate more than you consume. Research by the United States Army on caffeine and dehydration confirms that coffee is an acceptable source of fluids for athletes, even during exercise in the heat. Hence, coffee and other caffeinated beverages such as tea or cola count towards water intake.
  • An increased concentration of particles in the blood triggers the sensation of thirst. If your child weighs 150 pounds, he will start to feel thirsty once he's lost about 1.5 to 3 pounds through sweat (1% to 2% of body weight). Sweat loss of more than 10% body weight is life-threatening.
  • Body water absorbs heat from the working muscles and sweat dissipates the heat. That is, the evaporation of a liter (about 36 ounces) of sweat from the skin represents loss of about 580 calories. Sweat keeps your child or teen from overheating during exercise and in hot environments.
  • To determine how much water your child has lost through sweat, she should weigh herself (with little or no clothing) before and after an hour of hard exercise with no fluid intake. The change in body weight reflects water (sweat) loss. A one-pound drop in weight equates to loss of 16 ounces of sweat. A two-pound drop equates to 32 ounces-that's one quart. She needs to drink accordingly during her workouts to prevent that loss!
  • When an athlete sweats, they 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% 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, they are less likely to experience reduced performance, even at 3% dehydration. Three to 5% 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 ~2% for each percent body weight lost by dehydration. That means, if your son or daughter weighs 150 pounds and lose 3 pounds sweat (2% dehydration), their 8-minute mile slows to an 8:19 pace. That's preventable!
  • Adequate fluid intake can reduce problems with constipation and urinary tract infections. There is no scientific validation of theories that excessive water intake will improve weight loss, remove toxins, or improve skin tone.
  • The "drink eight glasses of water a day" advice is a myth.  There is no scientific evidence to supports such rule.  Drinking in response to thirst is okay, monitoring the volume and color of urine, is better, and weighing-in before and after exercise is best for monitoring hydration status.
  • Is bottled water better 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% get recycled. Drink plenty of water, but think "green."

Visit the MomsTeam Hydration Center for comprehensive information about hydration, dehydration, and heat illness.

Nancy Clark, MS, RD, CSSD (Board Certified Specialist in Sports Dietetics) is a MomsTeam nutrition expert


Armstrong, L, Pumerantz A, Roti M, et al.  Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption. Int J Sport Nutr Exerc Metab 2005;15:252-265

Koslo, J. Water, hydration and health: What dietetics practitioners need to know, SCAN's Pulse, Academy of Nutrition and Dietetics, 2012 31:1

National Academy of Sciences. Institute of Medicine. Food and Nutrition Board.
Dietary Reference Intakes for Water

Wilmore J, Costill D. Physiology of Sport and Exercise (Human Kinetics 1994).

Posted February 6, 2012