Dehydration

Dehydration literally means the removal of water. During the day you lose water when you go to the bathroom, sweat, and even when you breathe. Mild dehydration is indicated by increased thirst, decreased urine volume, abnormally dark urine, and unexplained tiredness. As dehydration progresses, symptoms can include headache, muscle cramps, sudden episodes of blurred vision, decreased blood pressure, and dizzy spells or fainting. Dehydration is serious! If left untreated, dehydration can result in delirium, unconsciousness, or even death. This is not meant to scare you, but to make you aware that you need to give yourself a constant supply of fluids throughout the day.
 
Even if you lose as little as 2% of your body mass through water lost it can have a negative impact on important body functions. The water in your body is important for regulating your internal temperature. So if you lose too much water, this could result in heat exhaustion or heat stroke. This is why it is so important to drink plenty of fluids while you are exercising, whether you are outside on a hot and humid day or a cold and dry day. Sweating rates increase with increasing temperature and humidity and it is not uncommon for a person to lose 2% to 3% of body mass during a workout. This is a lot of water! And you need to make a conscious effort to replace all of this fluid even if you don’t feel thirsty.
 
In order to prevent dehydration, one rule of thumb is that if you are perspiring, you should be drinking small, frequent sips of water. It is important to realize that during exercise, the sensation of thirst lags behind the need for fluid replacement. This is why relying on thirst alone may be insufficient. One simple way to determine how much water you should drink during exercise is to measure your fluid loss by weighing yourself before and after an exercise session, and replace every pound of weight lost with 20 ounces of fluid. Another way to prevent dehydration is to monitor the frequency and character of your urine. If you are urinating frequently and your urine is pale or colorless, it is likely that you are well hydrated; if you are not urinating often and your urine is deeply colored, it is time to drink up.