Considering that anywhere from 45% to 75% of our bodies are water (varies with fat mass – the more fat tissue the less water), it’s no wonder our bodies crave it. The amount we should consume to maintain a proper level is dependent on a number of conditions: our body size and surface area, activity level, sweat rate, metabolism, diet composition and environmental conditions. Exercising muscles can generate heat at a rate of 100 times that of inactive muscles. Athletes working out in hot, humid environments need to be extra cautious about replacing sweat loses and maintaining a safe internal body temperature. Even in winter months when we don’t sweat as much during activity, we must be careful to drink enough fluids. Our bodies can lose a lot of fluid from breathing in cold, dry air, then exhaling air that is filled with our body’s moisture.
Athletes or exercisers can lose 1 to 2, even 3 or more, liters of fluid per hour during periods of vigorous activity, particularly in hot, humid environments. (Performance can suffer after losses of 1 to 2 liters of fluid.) Fluids are lost by several means – the kidneys (excreted as urine), gastrointestinal tract (feces), respiratory tract (breath) and skin (sweat). We must replace these fluids by consuming fluids in the proper amounts at the right times prior to, during and after activity. Although various factors dictate how much fluid should be consumed, general recommendations for activity are as follows:
- Drink 16 ounces 2 hours before activity
- Drink 8 to 16 ounces about 15 minutes prior to activity
- During activity:
- Drink anywhere from 4 to 16 ounces of fluid every 15 minutes
- During lengthy, strenuous activity in the heat, particularly if lasts more than an hour, consume fluids with small amounts of electrolytes, such as sports drinks
- Drink 24 ounces of fluid for every pound of body weight lost during activity
- Another way to determine hydration status is urine color. The darker the urine, the more dehydrated. Drink until urine color is fairly clear.
Consuming plenty fluids and healthy, fluid-containing foods in the diet, such as fruits and vegetables, on a daily basis will help keep you hydrated. Approximately 20% of our daily fluids come from food. A good, balanced diet will also replace electrolytes (e.g. sodium, chloride, potassium, magnesium) lost during activity. Maintain a healthy diet with plenty of fluids so that you’ll be at peak levels of hydration and won’t begin your workout in deficit.