Dehydration is the excessive loss of the body’s water. When water leaves the body, especially through sweat, it takes electrolytes with it. Electrolytes like magnesium, calcium, potassium, and sodium all are necessary for muscular function. When the body loses water, so do the body’s cells. Water is necessary for metabolic function. Some symptoms of dehydration are headaches, muscle cramps, muscle fatigue, and in very serious cases it can cause seizures.
Most of the human body is made up of water. The typical range is 50% to 75%. This should tell you how important water is to the body and its metabolic functions. The thirst mechanism is the first sign of dehydration. Dark yellow urine can also indicate low hydration levels. You should not wait until you are thirsty to take in fluids, especially while training. Men should intake at least 3 liters of water and women should drink 2.2 liters. If you sweat a lot during training then the amount should be higher.