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When normal conditions exist in the body, various mechanisms preserve fluid and electrolyte balance. If the mechanisms fail due to illness, stress, exercise, climate variations, supplements, foods, or beverages, life threatening imbalances may occur.
Symptoms of dehydration include:
• dry skin
• fatigue and weakness
• increased body temperature
• muscle cramping
• darker-coloured urine
• dry mucous membranes (mouth, nose, eyes)
Severe dehydration can also include:
• muscle spasms
• dark urine
• vision problems
• loss of consciousness
• kidney and liver failure
Stuff to know…
During exercise, we need more water. The increased metabolic rate of muscle exertion requires a larger amount of nutrients and oxygen along with faster waste and heat removal from the body.
So where do we get fluids to maintain balance? Well, remember that water intake doesn’t come only from drinking water. It also comes from tea, coffee, non-dairy milks, milks, and water from solid foods. With thirst as a guide, humans are generally well hydrated. There is extreme variability in water needs based on climate and physical activity levels.
For men, an average of 16 cups of water a day from fluid and non-fluid sources (e.g. fruits and vegetables) is adequate; for women, an average of 11 cups.
Ever wonder why IV fluids are typically given as normal saline? Well, normal saline is 0.9% concentration, similar to that of blood (isotonic).
Be aware of thirst cues.
If no fluids are going to be given during exercise, you can pre-hydrate with the following regimen:
• 500 ml of fluid on the night before exercise
• 500 ml in the morning
• 500 to 1000 ml, 1 hour before exercise
• 250 to 500ml, 20 minutes before exercise
Consume nutrient dense foods/beverages after exercise to assist in the re-hydrating process.
Those with a history of cramping and “salty sweat” should consider adding salt to foods/beverages after exercising (a quarter to one-half teaspoon).
For every pound of sweat lost during exercise, rehydrate with 2 cups of fluid.
Dark colored urine can be indicative of a low water reserve in the body. So make sure your urine is light-colored and clear.
Journal of the American Dietetics Association (Volume 99, number 2, pages 200-206, 1999) that discusses water needs. In this paper, the author states that:
"To be well hydrated, the average sedentary adult man must consume at least 2,900 mL (12 c) fluid per day, and the average sedentary adult woman at least 2,200 mL (9 c) fluid per day, in the form of noncaffeinated, nonalcoholic beverages, soups, and foods. Solid foods contribute approximately 1,000 mL (4 c) water, with an additional 250 mL (1 c) coming from the water of oxidation."