On Sun, 14 Aug 2016 22:51:36 -0400, Frank Krygowski
wrote:

On 8/14/2016 9:56 PM, John B. wrote:


Your post inspired me to do a little research on "dehydration" and it
turns out that related to exercise it is a fairly complex subject.
Bicyclists apparently drink all the time while the top level
marathoners drink relatively little and typically lose 7 to 8 pounds
during a race, about 3 - 4 liters of water, or 6 to 8 bicycle bottles.

I'll have to ask the family marathoner about that.


Actually I cheated a little, it ain't all water. The top guys and a
lot of the little guys glycogen load and are carrying probably 2 kg.
extra weight, say 500 grams of glycogen, stored in the liver, and the
necessary 3 grams of water required to store each gram of glycogen, at
the start.


In addition when one begins to lose water content one doesn't
immediately become thirsty and after water is imbibed it takes as much
as 20 minutes before your body has absorbed it into the body's fluid
systems and adding complexity is that chemicals in the water determine
how quickly it will be absorbed. GaterAid was not originally designed
as a "sports drink" but as a liquid that the body absorbed faster than
pure water.

Given that the human body has a sort of sell leveling fluid system the
logical thing to do is to drink as much as possible, as often as
possible, as the body's automatic volume control will eliminate any
surplus :-)

Commenting on those two paragraphs together: My only double century was
done on a very hot summer day. The worst of it happened at about mile
130 (IIRC) when I was feeling very dehydrated, but at the same time very
uncomfortable because of a belly full of water. I could actually feel
it sloshing around in there.

It eventually occurred to me that I was hyponatremic. I ate a bunch of
salt packs from a fast food restaurant and almost immediately felt better.

So "drink as much as possible" may make sense, provided the proper
electrolyte balance is maintained. These days, if a ride's anticipated
to be long and hot, I'll sprinkle some salt substitute into my water
bottles before filling them. It's got sodium chloride, plus potassium
chloride and magnesium sulfate. The brand name is "Cardia Salt".

BTW, a good friend swears by V-8 Juice for those hot sweaty rides. I
find it works, too, and it's easy to find at remote convenience stores.
--
cheers,

John B.