DehydrationThe basic rule of thumb is to start a walk having had 16 oz. of water (a pint or half liter), then replenishing with a cup of water every 15-20 minutes. That is about a water bottle-full an hour, about a half liter or pint. End your walk with a big glass of water. That will prevent dehydration - losing too much fluid from your body. New guidelines in 2003 tell distance walkers and runners to drink as soon as thirsty.
Signs of dehydration: Dry mouth, fatigue, dizziness, stomach ache, back pain, headache, irritability, decreased urination.
Hyponatremia (loss of sodium or body salt)Sweating removes both water and salts - electrolytes - from your body as you walk. Depending on the humidity, you may not notice how much you are sweating. For walks of over an hour, replenishing your electrolytes with sports drink is also important to prevent hyponatremia. It is recommended to drink 1 bottle of sports drink for every 2 bottles of water. Eating salty snacks such as pretzels before and during long walks is another source of salt. New guidelines in 2003 emphasize not overdoing it on plain water, as some walkers drink more than the recommended water amount and flush out their body salts, ending up sick with hyponatremia. Do not overdrink at the end of you walk, either. Be sure to have salty snacks or sports drink after your walk.
Signs of hyponatremia: nausea, headache, cramps, confusion, slurred speech, bloating and swollen hands.