Hydration: How long does it take to rehydrate

Proper rehydration is more than just drinking 32 oz right after a run. It goes hand in hand with proper nutrition. Lots of fruits and veggies, drink all day, keep your drinking at night to less than a twelve pack.

I believe we can absorb roughly 32 oz per hour. So if you lose a gallon of sweat (~ 8 pounds) on a run, it will take at least 4 hours to recover.

Noakes estimates that the average runner can absorb somewhere between 400 and 800 milliliters per hour

Th context of that quote is while running. I'm not sure if the body absorbs any slower or faster while at rest.

Here's the deal, when you lose a lot of water from exercise, that water came from both extracellular fluid (blood plasma mostly) and intracellular fluid (the water inside your cells). When you get dehydrated, your kidneys will reabsorb more of the water that is filtered making more concentrated urine. In order to rehydrate properly, you will ingest water which will be put into your blood (as plasma), and then some of this water will enter your cells to bring them back to normal levels. This second part takes much longer than the first part. When you chug a bunch of water when dehydrated, that fluid enters your bloodstream much more quickly than the cells in your body can absorb it. Your kidneys sense that there is too much fluid and causes you to pee it out, along with some solutes such as Na+ and K+ (which you are likely already low on if you've been sweating a bunch). So, by chugging a bunch of water while dehydrated you actually aren't rehydrating very well and losing further increasing your loss of electrolytes. This is why it's better to rehydrate somewhat slowly. I don't know what that means in number of ounces or minutes, but you can usually just listen to your body. Drink until your thirst is quenched initially, then drink some more in 15min or so when you start to get thirsty again.

I just spent a whole week dehydrated, weak, listless, running terribly, and never able to get the hydration, etc. right. I'm still not 100 percent. Once you are really far gone it is tough to fix. I only started to feel better after pulling a Kempainen on the "run" home last night. Any suggestions other than drink gradually?

what did you use to rehydrate? Just using a LOT of water is a bad idea (unless you eat a good amount, with salt and other nutrients around that time). Because as we all know, this can lead to hyponatremia (at the risk of stating the obvious: you sweat out a lot of salt with the water you lose. Only replacing the water dilutes your blood (serum). Water moves from the extracellular fluid to inside the cells to balance the concentration on each side. This can lead to swelling of brain cells). Also, large amount of water taken at once will often be peed out fairly quickly, therefore causing you not hydrate very well.

As others mentioned, you need electrolytes to better absorb and maintain fluid. Adding carbs and proteins further enables one to maintain fluid better than just taking in water (due partly to slower gastric emptying). Milk has all of these. Milk is actually the best hydration drink you can consume. but of course, some combination of plain water, milk, juice, gatorade, and food will do the trick, and not only rehydrate you, but aid in glycogen resynthesis and protein rebuilding.

In response to the OP, first, see what I wrote above, and second, one needs to take in more water than they sweated out during a workout in order to rehydrate due to urine loses and further sweating post workout.

jjjjjjjj wrote:

I only started to feel better after pulling a Kempainen on the "run" home last night. Any suggestions other than drink gradually?

What is "pulling a Kempainen"?

+1, Thanks for that explanation.

Do you even Gatorade?

When you become dehydrated your blood volume slightly drops, so you have slight hypovolemia. When you drink a lot of water quickly, the water enters the blood and corrects hypovolemia even more than needed, which slightly increases the blood pressure, what will trigger water excretion through the kidneys and you will excrete clear urine - but to be rehydrated the water needs to enter your body cells not only blood. This means you can excrete clear urine while still dehydrated.

The difference between hypovolemia and dehydration is described here:

http://www.ehealthstar.com/hypovolemia

It is your body weight loss that tells you how dehydrated you are. A common recommendation is to drink 1.5 liters water for every kilogram of weight loss and the same recommendation says to replace one half of the total amount of water needed in the first four hours.

http://www.nata.org/sites/default/files/FluidReplacementsForAthletes.pdf

If soon after drinking you excrete copious amounts of urine you drink too fast.

Consuming regular salted foods along with drinking helps to retain water in your body.

I'm not aware of any specific water absorption limit. I personally have drunk 4 liters of water in 20 minutes in one occasion when I was quite dehydrated. I don't recommend doing this to anyone since it can actually cause hyponatremia.