Practical Hydration

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Hydration is complex and controversial, but this page gives simple, practical advice based on The Science Of Hydration. The basic guidelines to follow:

  • Drink to thirst, as you thirst works remarkably well and mild dehydration is not as much of an issue as was once thought.
  • If you're sweating heavily, increase your salt intake. I recommend adding 1/4 to 1/2 teaspoon of salt to each quart/liter of drink.
  • Don't drink to ease your suffering, only to quench thirst. If you're not thirsty, drinking won't help your misery.
  • Don't drink a fixed amount; let your thirst guide you.
  • If you're thirsty, don't skip drinking to make up time; unless you are very close to the finish, you'll end up slower.
  • Don't start your run thirsty - it is better to hydrate before you start than to try to 'catch up' on the run. However, drinking lots of water before a run without plenty of electrolytes is a bad thing. This practice can flush out electrolytes, creating a problem ahead of time.

1 Symptoms and Possible Meanings

These are suggestions and guidelines rather than firm rules, so apply with caution and common sense.

  • Thirsty. If you're thirsty, drink.
  • Thirst and Urination. If you are thirsty, but everything you drink creates urine without quenching your thirst, you may be low on electrolytes.
  • Swollen Hands. The most likely cause is lack of electrolytes, but can also be triggered by re-hydration following prolonged dehydration. (There are other possible causes outside of hydration.)
  • Skin Turgor. When you pinch the skin on the back of your hand and release, it should spring back into shape. If it moves back slowly, you may be dehydrated. If it 'tents', then you may be badly dehydrated.
  • Salt Stains. These salt stains on clothing, or a salty crust on the skin are sometimes considered a sign of 'salty sweating'. I do not believe this is the case, but rather an indication that conditions are producing a lot of sweat that is evaporating quickly and leaving the salt behind. Cooler conditions produce less sweat, and warmer/humid conditions cause the sweat to roll off, taking the salt with it.
  • Lack of urine. This can be a sign of dehydration, but not always. One cause of Hyponatremia is a hormone that stops you producing urine. If you are not producing urine but are not thirsty, it's okay to take a small drink to see if this triggers your thirst, but nothing more. Dehydration is self-correcting and rarely causes a problem, but over-hydration is dangerous and can be fatal.

2 Weight Drop from Dehydration

If you weigh yourself before and after you run the difference between the two numbers will be the change in body water. However, on a longer run (~16+ miles), you will lose about 4 pounds due to burning off carbohydrate (Glycogen). So if your weight has dropped 0-4 Lb, you're probably hydrating okay. If your weight has dropped much more than 4lb, you may need more fluids and possibly electrolytes. If your weight has gone up, you probably need more electrolytes.

3 What to drink?

Drinking just water is fine most of the time as long as you're not sweating a lot and on a low sodium diet. For shorter runs (marathon or less), salty snacks after the run may be sufficient, depending on how much you sweat and how long the race takes you. For longer runs, you may need to consume salt during the run. I drink water with 1/4 tsp of salt per quart as a cheap solution, or make up my DIY Electrolyte Drink. Many people use a sports drink, but these rarely contain more than trivial amounts of electrolytes. While Electrolyte Capsules can be useful, I recommend avoiding them because they bypass the sense of taste. Our taste for salty things reflects our sodium balance. Electrolytes other than salt (sodium) are important, but generally not critical in the short term.

  • I often add a pinch of 'no salt' (potassium chloride) to my drink to give me a bit of potassium.
  • Magnesium is vital for mental functioning, reducing migraine and maintaining performance.
  • Eating a nutritious diet is important to get a variety of micronutrients. (Bananas have a lot of potassium, but potatoes have more.)

4 The Fellrnr Drinks

Pre-run - 24-32 oz of fluid with 1/4 tsp salt about an hour before the run. This gives my body a chance to keep or flush out the fluids and electrolytes. (I also take a pinch of potassium salt ('No Salt') and a magnesium supplement before the run.) For training runs where I don't need extra calories, I drink add 1/4 tsp salt, plus a pinch of 'no salt' to each quart of water. This tastes a little odd, like very soft water. For races, or training runs where I want extra calories, I use Gatorade with the same extra 1/4 tsp salt, plus a pinch of 'no salt' to each quart. This makes the Gatorade taste very strong - try it before you run with it.