On one recent hike I was feeling sluggish after a couple days. I realized that I had been a bit dehydrated and was running low on electrolytes. Here's a portion of a book I'll be releasing soon about diet and nutrition on the trail:
After about 90 minutes of hiking, sometimes longer or shorter depending on temperature, we will lose enough water through sweating to affect performance levels. Water is vital. It transports nutrients, regulates body temperature, lubricates joints and organs, and helps preserve cardiovascular function.
Along with fluid loss comes loss of electrolytes such as sodium, potassium, and chloride. These minerals come out in our sweat. If you have ever noticed white sweat rings on your cloths after a good workout or a tough hike, these are the electrolytes we sweat out. These electrolytes are needed to regulate nerve and muscle function, balance blood acidity and pressure, and help rebuild tissues stressed during physical activities.
How often should we replenish our bodies with fluid? That depends on several factors, and everyone is different, but a good rule of thumb is to stop at least every two hours to drink a liter of water with electrolytes. Electrolytes can also come in the form of sodium in food; water and a salty snack will do the trick. The amount of fluids and electrolyte replenishment will depend on temperature and how intense the hike is.
The danger of not getting enough fluids is, of course, dehydration. Dehydration is when the body is starved of fluids required to maintain normal body functions.
Feeling thirsty is usually a sign that we are already dehydrating. Other symptoms of dehydration include less frequent urination (this should happen at least every couple hours), dark colored urine (darker than lemonade), fatigue, dizziness, muscle cramping, and even confusion. Allowed to continue, dehydration can manifest in other ways: heatstroke, depression, constipation, hypertension, kidney stones, uremia, gallstones, intestinal failure, seizures, hypovolemic shock, and joint complications. Dehydration is no joke.
Hydrate often. Every two hours will help keep the fluid supply where it should be, so you stay healthy on the trail. If it helps, set an alarm on your phone or wristwatch as a reminder.