4. Your body parts have different water contents.
Water constantly moves through your cells. About 4 percent to 10 percent of your body-water gets replaced every day with "fresh" water. For example:
- Blood is approximately 93 percent water.
- Muscle is about 73 percent water.
- Body fat is about 10 percent water.
5. Bioelectrical impedance (BIA) methods of measuring body fat actually measure body water.
This 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 fat.
6. Your body produces 8 to 16 oz. (250 to 500 ml) water per day.
This occurs during normal metabolic processes. During a marathon, a runner's muscles can produce that much water over two to three hours. When muscles burn glycogen, they simultaneously release about 2.5 units water for every 1 unit of muscle glycogen; this helps protect against dehydration.
7. Your coffee is a 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.
Army research on caffeine and dehydration confirms 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 your water intake.
8. An increased concentration of particles in your blood triggers the sensation of thirst.
If you are a 150-pound athlete, you'll start to feel thirsty once you've lost about 1.5 to 3 pounds of sweat (1 percent to 2 percent of your body weight). You are seriously dehydrated when you have lost 5 percent of your body weight.
9. Body water absorbs heat from your muscles and sweat dissipates heat.
The evaporation of 1 liter (about 36 oz.) of sweat from the skin represents a loss of about 580 calories. Sweat keeps you from overheating during exercise and in hot environments.
10. You can measure your water losses after a workout.
To determine how much water you lose when you sweat, weigh yourself (with little or no clothing) before and after one hour of hard exercise with no fluid intake. The change in body weight reflects sweat loss. A one-pound drop in weight equates to loss of 16 oz. of sweat. A two-pound drop equates to 32 oz.—that's 1 quart. Drink accordingly during your workouts to prevent that loss.