How fast does water go from your mouth to your tissues?

Factual Questions
1

I’ve been riding my bike to work for the last week or so, and I’ve noticed a strange thing.

If I don’t drink a lot of water before I set out, I hardly perspire at all, and it’s difficult to ride. My muscles don’t respond as quickly or with as much strength as when I do have enough water, and I get really, really hot. As soon as I drink a bottle of water, I sweat a lot**, and feel much stronger. After a while, the sweating stops, and it gets harder to ride, so I stop and drink more, then the cycle (haha!) continues.

My guess is that I’m not dehydrating, as such, but my body is getting a signal that water is scarce, then switching into rationing mode. I drink, generating a signal that water is available again, so I go back into wasteful mode.

So anyway, I guess my question is twofold:
a) Is my guess above, about how the body works regarding water conservation, correct?
b) If a person really was dehydrated (to a dangerous degree), how fast would water get back into the system and rehydrate their tissues? Are we talking about seconds after drinking? Minutes? Hours?

Ok, it’s threefold. c) Is there anything I can do to help speed my adjustment to the climate? I mean is there any sort of diet modification or supplement that will help, or do I just need to tough it out for a few summers until I adjust naturally?

**[sub]When I’m riding in the summer, sweat literally almost pours off my forehead, as if I had dumped a cup full of water over myself. I never had this problem when I lived in NM, so I assume that this is what is happening: When I overheat here, since sweating doesn’t cool you off when humidity is high and water can’t evaporate much, my body says “wow, I’m not cooling off…better sweat more!” And it escalates to an almost cartoonish level.[/sub]

2

As a person who bikes centuries in seriously hot weather, I can tell you that you need to stay hydrated, not just try to reach a level of wetness once you feel thirsty. If you don’t start drinking until you feel thirsty, it’s already too late.

Keep well hydrated all the time. When you know that you are going to exert yourself in hot weather, start increasing your fluid intake several hours beforehand. If it’s going to be a few days of exertion, start a day or two early with the hydration.

Also make sure you are getting rid of liquids at a fairly frequent rate. If you are drinking lots of water and not urinating, something is wrong.

Also, add in a little gatorade or some kind of electrolyte drink. Otherwise all that water will wipe out your electrolytes and you’ll be just as bad off.

To your question, I am not sure exactly how long the water takes to get into your system, but it does take some time. If it happened within minutes there would be no need to put dehydration victims on IVs.

3

That’s interesing, I didn’t know that was important. Thanks for the tip. I doubt it will make my ride any easier, but at least I won’t be destroying my body at the same time. :slight_smile:

Getting rid of liquids is not a problem. The last few days during my ride (about 9 miles, I do it in about 50 min including two stops to drink), I’d estimate that I sweat out pretty close to the amount that I drink, if not more, within about 10-15 minutes. Is that a problem?

Huh, hadn’t thought about that. But, some of the time patients aren’t given water orally to avoid vomiting, because I guess the stomach isn’t able to handle it under certain conditions (like after surgery or trauma).

Thanks for the info.

4

To answer the question generally, a drug (such as nitroglycerin) absorbed sublingually takes about 10-15 seconds to achieve a systemic effect through the circulation.

5

yeah, nitro works great sublingually, but water isint absorbed highly through the sublingual route.
the great kicker is once you get profoundly dehydrated one of the first things your body turns off blood supply to is your gut – no blood there = you throw up anything you drink/eat…thats why those who get really dehydrated get stuck with IVs and have lots of fluid pumped back into them

6

I’ve often wondered about that cliche where someone mistering to a severely dehydrated person always limits the amount they are permitted. Seen it a thousand times. Blood supply, huh.

So, it is therefore common that when water is supplied, the blood rushes to the gut, and the dehydration victim loses erectile function?

If Bob Dole drank more water, he wouldn’t have humiliated himself on TV?

But seriously folks: thanks. I’ve often wondered why anyone who desperately needs water would puke when he gets it.

7

thats a good question :wink:

IIRC – I know for a fact that digestion is a parasympathetic response, and I belive that the erectile response is also a parasympathetic response, so I would guess that active digestion shouldnt pull any blood away from other such responses, but thats simply a guess.

the reasion that you have less blood to the gut is because as you loose fluid your actually going into a state of shock – your not loosing red blood cells to the outside of the body, but the fluid to carry them is disappearing (hypovolemia) – so what fluid you do have is diverted to the imporntant stuff, and at that moment your gut isint one of them.

8

Parasympathetic? Is that like some guys who pretend to give a shit but are only interested in nookie? And should I drink a big glass of water before I’m, like, parasympathetic. If I was gonna be.

9

okay okay, a picture is worth a 1000 words

http://jimswan.com/anatomy/parasympathetic_division.gif

http://jimswan.com/anatomy/sympathetic_division.gif