Calculating fluid (sweat) loss -- account for glycogen?

"Tom B." <[email protected]> wrote

>I just tried this for the first time today; weighed myself before and
> after a run. It was an incredibly miserable day here in Baltimore, so
> I expected a loss, but I was shocked at how much it was.

> temp/RH = 81 deg/82%

Much more telling than relative himidity, is dewpoint (dp). DP is about 75
degrees today in Baltimore, which is unbelievably sticky for us out west.

A dp of 75 means that a glass of water at room temperature (anything under
76 degrees) will have condensation forming on the outside -- that's a lot of
water in the air.

In LA today, DP is about 60 degrees, enough so that I was soaked, with sweat
dripping down my legs after today's trail 9 miler, but the breezes were
cooling, and I didn't overheat.

> dist/time = 15.14 mi/1:43:10 (medium intensity, ~30 sec/mi slower than
> MP)

Given the conditions, that's quite a strong effort, actually, I'd say it was
equivalent of MP in more humane conditions. The question of the hour is,
how trashed will you be tomorrow?

> fluid intake = 32 oz
> net weight change = -5.5 lbs!!!

Pretty amazing, eh. I lost 7 lbs during 1:44 at my last race (a mountainous
1/2 marathon)

> I thought I could get away with just one extra-large water bottle, but
> obviously this was not enough by a long shot. I sipped it pretty
> slowly, but it was finished by mile 12.

It's easier when you're not dehydrated...

> So what I'd like to figure out here is how much more fluid I would have
> to take in to stay hydrated. 5.5 lbs is 5.5 extra pints, but shouldn't
> I use a lower number to account for glycogen depletion during the run?
> If I just take a wild guess that 50% of my calorie burn was glycogen,
> that would be about 60 kcal/mi = 900 kcal CHO = 225 g * 4:1 (?) for
> water needed for storage = approx 2 lbs.

I assume that I've got 2-3 lbs of glycogen in the tank. I consider a long
or hard effort (such as yours) to be a hydration success if I'm down only 2
lbs.

> So this leaves me with 3.5 pints deficit, which I probably wouldn't be
> able to drink in such a short interval anyway. But I could probably
> drink 2 extra pints if I stash a second bottle on my course.

Sure you can drink that. I've trained myself to drink up to 40 oz/hour
(approximately your sweat rate today).

I plan my hydration strategy for each run (I never run less than an hour).
I usually run on trails with water available every few miles, and can get by
most of the time with a 1 or 2 bottle pack. I carry cytomax powder in a
plastic bag and mix my brew at the water stops. For some reason, water
tastes like cardboard to me on long runs and I crave a bit of flavor. The
carbs in the sports drinks (~200 cals/hour) also feed your legs.

If you find yourself not thirsty, sloshing, or slightly queasy during your
runs, and are therefore unable or unwilling to drink, that's a sign of low
salt (read up on Succeed caps). If you replace the salt you sweat, your
thirst should keep pace with your dehydration.

> Comments, anyone? (Dan? Donovan?)

How's that??

-- Dan

I never saw my original post in Google groups, but did see your reply,
Dan. Not sure what Google is up to.

Dan Stumpus wrote:
> "Tom B." <[email protected]> wrote
> > dist/time = 15.14 mi/1:43:10 (medium intensity, ~30 sec/mi slower than
> > MP)
>
> Given the conditions, that's quite a strong effort, actually, I'd say it was
> equivalent of MP in more humane conditions. The question of the hour is,
> how trashed will you be tomorrow?

Felt sore the next day (which is today), but I think that was more due
to jumping back into running after a layoff with a big effort -- just
got back from an 11-day, ~1000 mi bike trip in OR/CA, and all that
cycling really did a number on my running form. But it was so worth
it.

> Pretty amazing, eh. I lost 7 lbs during 1:44 at my last race (a mountainous
> 1/2 marathon)

I thought you had this hydration problem licked...

> > that would be about 60 kcal/mi = 900 kcal CHO = 225 g * 4:1 (?) for
> > water needed for storage = approx 2 lbs.
>
> I assume that I've got 2-3 lbs of glycogen in the tank. I consider a long
> or hard effort (such as yours) to be a hydration success if I'm down only 2
> lbs.

It sounds like you're agreeing with me, in a roundabout way.

> > So this leaves me with 3.5 pints deficit, which I probably wouldn't be
> > able to drink in such a short interval anyway. But I could probably
> > drink 2 extra pints if I stash a second bottle on my course.
>
> Sure you can drink that. I've trained myself to drink up to 40 oz/hour
> (approximately your sweat rate today).

I think I'll shoot for 24-32 oz/hr on the next miserable weather
long(er) run. I've just started a somewhat accelerated marathon
buildup (Oct 15) with this 15-miler, which was the reason for rushing
my return from cycling. So I will have a few more chances to suffer in
the crappy summer weather here. I will probably try sports drink next
time, and might even add some salt. I can think of a few places to
stash bottles, but it's a pain to drive them out there beforehand.

> > Comments, anyone? (Dan? Donovan?)
>
> How's that??

Thanks for the input, Dan.

Dan Stumpus wrote:
> "Tom B." <[email protected]> wrote
>
> Sure you can drink that. I've trained myself to drink up to 40 oz/hour
> (approximately your sweat rate today).
>

Without extra pee breaks?

"Tom B." <[email protected]> wrote

>> Pretty amazing, eh. I lost 7 lbs during 1:44 at my last race (a
>> mountainous
>> 1/2 marathon)
>
> I thought you had this hydration problem licked...

Actually, I drank 20 oz during, so net loss was only 5.75 lbs. I made a
conscious choice to just hang in there for such a short race, and do more or
less what the other guys I was competing with were doing (which is drinking
very little).

I normally race ultras, where I'm out there for 5-9 hours, so I thought I'd
see what happened at a short event. I was able to maintain my pace despite
the loss, but it was a cool and overcast day. There may be some kind of
trade off of weight versus dehydration under these conditions.

-- Dan

"timeOday" <[email protected]> wrote

>> Sure you can drink that. I've trained myself to drink up to 40 oz/hour
>> (approximately your sweat rate today).

> Without extra pee breaks?

I drank over 40 oz/hour throughout the Avalon 50 miler in April, and only
needed one stop (in an 8+ hour race). I was also taking Succeed caps. I
think if you drink what you need that pit stop frequency isn't affected
much.

-- Dan

>I never saw my original post in Google groups, but did see your reply,
Dan. Not sure what Google is up to.>

It's a personal vendetta against you. Actually a lot of posts are
missing the last few days, not uncommon for a weekend on Google.

I just ran 10 miles in 85' with humidity at 74%, and I lost 1lb. When I
hear stories like "I lost 7lbs running today" I cringe. I mean that
can't be healthy, and it leads me to believe you are overhydrated. I
drank plenty all day yesterday, and this morning prior to my run, so I
was well hydrated, and I sweat accordingly. But 7lbs? I think if you
have 7lbs of water to sweat out, you have to be overhydrated.

>I think if you drink what you need that pit stop frequency isn't affected much.>

I believe that too. People who stop 2,3,4 times to go to the bathroom
drank and/or ate too much.

On 2005-07-18, Tom B. <[email protected]> wrote:
>> I assume that I've got 2-3 lbs of glycogen in the tank. I consider a long
>> or hard effort (such as yours) to be a hydration success if I'm down only 2
>> lbs.
>
> It sounds like you're agreeing with me, in a roundabout way.

FWIW, I also agree with your comments.

I don't think being down 5lb or so is going to kill you, but the last 5
miles or so probably will be easier if you drink a little more.

Do you have access to any drink fountains so you can top up your bottle ? I
never carry drink with me.

> I think I'll shoot for 24-32 oz/hr on the next miserable weather
> long(er) run.

I suppose you've already got this covered -- but do you drink before the run ?
If you take say 16oz before the run, that's 16oz you don't need to hand-carry.

Trying to "water load" before a run is a bad idea, but being in a well hydrated
state with a full tank -- a few pounds up from average weight -- is probably a
good thing.

For example, my normal weight is about 153 now. If I start the run at 148, even
losing 3lb is probably going to leave me pretty trashed. But if I start at
154-155, I could drop 4-5lb and still feel pretty good.

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/

<[email protected]> wrote in message
news:[email protected]...
>I just ran 10 miles in 85' with humidity at 74%, and I lost 1lb. When I
> hear stories like "I lost 7lbs running today" I cringe. I mean that
> can't be healthy, and it leads me to believe you are overhydrated.

Yes, it's likely not healthy but it's not the absolute amount but the
amount of loss for your weight. If you started at 140 pounds then you
are 5% and in any race that has scales, it would be demanded that you
park your ass in a chair and hydrate to get you weight back up. 1-3 %
the EMT's will suggest you drink more but continue. 4-5% they will
suggest you sit and rehydrate(this included food), 6-7% your tag is cut
and pulled from the race.

I some of my races I hydrate properly and drink half the Mississippi
River during the race and still lose 5 pounds. Believe me there is
easily 7 pounds of fluid in the average person that could be lost. I
know some ultra guys 240 and 7 pounds would a little perspiration.


> drank plenty all day yesterday, and this morning prior to my run, so I
> was well hydrated, and I sweat accordingly. But 7lbs? I think if you
> have 7lbs of water to sweat out, you have to be overhydrated.

You can NOT extrapolate your sweat rate to anyone but yourself.

-DF

>Yes, it's likely not healthy but it's not the absolute amount but the
amount of loss for your weight. If you started at 140 pounds then
you
are 5% and in any race that has scales, it would be demanded that you
park your ass in a chair and hydrate to get you weight back up. 1-3 %
the EMT's will suggest you drink more but continue. 4-5% they will
suggest you sit and rehydrate(this included food), 6-7% your tag is cut

and pulled from the race.>

Sounds complicated.

>I some of my races I hydrate properly and drink half the Mississippi
River during the race and still lose 5 pounds. Believe me there is
easily 7 pounds of fluid in the average person that could be lost. I
know some ultra guys 240 and 7 pounds would a little perspiration.>

Yeah but you do ultras, 7 lbs in 8 or 9 miles (as was mentioned
earlier) seems excessive. But I admit I've trained myself to run an
hour in any heat, without any needed hydration, or even feeling
thirsty. But I strongly suspect if I overhydrate I could do 7lbs on my
185lb frame fairly easily, but it isn't required, and probably not
healthy. I really never paid much attention to this in the past, as
it's never been a problem.

>You can NOT extrapolate your sweat rate to anyone but yourself.>

I didn't mean to sweetie.
TBR

>>You can NOT extrapolate your sweat rate to anyone but yourself.>

>I didn't mean to sweetie.

Yes, after all, everything's different for you ladies, Mildred.

[email protected] wrote:
> I just ran 10 miles in 85' with humidity at 74%, and I lost 1lb. When I
> hear stories like "I lost 7lbs running today" I cringe. I mean that
> can't be healthy, and it leads me to believe you are overhydrated. I
> drank plenty all day yesterday, and this morning prior to my run, so I
> was well hydrated, and I sweat accordingly. But 7lbs? I think if you
> have 7lbs of water to sweat out, you have to be overhydrated.

That seems a little hard to believe, even for someone who doesn't sweat
all that much. I assume you didn't drink anything during the run,
right? 1 lb is practically nothing -- only about 8 oz of sweat plus 8
oz of glycogen (I'm guessing on the split). 85 deg/74% RH is pretty
damn sweaty weather, and 10 mi is a pretty long run. Are you sure you
only lost 1 lb?

I know that runners can acclimate to the heat, but I didn't think this
meant less sweating -- just more-rapid, less-salty sweat.

Donovan Rebbechi wrote:
> I don't think being down 5lb or so is going to kill you, but the last 5
> miles or so probably will be easier if you drink a little more.

Agreed. It wasn't a big deal, but I'm sure I would have been more
comfortable at the end with more water. I just never would have
guessed such a dramatic weight loss. I don't know why I never tried
this test before, but the conditions were so unusually bad, and this
topic has been discussed a lot recently on r.r.

> Do you have access to any drink fountains so you can top up your bottle ? I
> never carry drink with me.

Not really. I have carried 2 26-oz bottles in a waist belt/pack
before, and it's not too comfortable. One bottle is not bad at all,
and I've had extremely good results carrying a single bottle in my 2
marathons (filling about every 10 miles from the aid stations, and then
drinking slowly as I go). To do a long run around here without
carrying any water at all would be virtually impossible.

> I suppose you've already got this covered -- but do you drink before the run ?
> If you take say 16oz before the run, that's 16oz you don't need to hand-carry.

I think I was pretty well hydrated before starting out, but will be
extra-attentive next time.

> Trying to "water load" before a run is a bad idea, but being in a well hydrated
> state with a full tank -- a few pounds up from average weight -- is probably a
> good thing.

I try not to drop too far below well-hydrated. I doubt I could tank up
to be any more than 1 lb over my nominal weight.

>That seems a little hard to believe, even for someone who doesn't sweat
all that much. I assume you didn't drink anything during the run,
right? 1 lb is practically nothing -- only about 8 oz of sweat plus 8
oz of glycogen (I'm guessing on the split). 85 deg/74% RH is pretty
damn sweaty weather, and 10 mi is a pretty long run. Are you sure you
only lost 1 lb?>

Well I did drink at a water fountain, a minimal amount, about 45
minutes into it, but that's it. I sweat pretty good in this heat, so
I'm not sure that applys. Ok, no I'm not sure, I just didn't feel any
lighter LOL! But the humidity was at 85%, mea culpa.

>I know that runners can acclimate to the heat, but I didn't think this
meant less sweating -- just more-rapid, less-salty sweat.>

I do seem to stay drier than my running companion, but then again she's
only 100lbs wet, runs nice and slow, and just looks awsome with her
waist length strawberry-blond wavy hair, in her cute little blue halter
top, as her cute lil butt twitches along... not relevant, I was just
bragging LOLOLOL!
Bill "who thinks he maybe in love" Rogers

>Yes, after all, everything's different for you ladies, Mildred.>

I'm Dougs kind of woman too, the kind with a package LOL.

Jumping in late and a little behind...

Muscle glycogen does account for some of the loss in weight, but calculating
it is going to be hard to do. Noakes addresses this in "Lore of Running,
4th edition" which is not handy at the moment.

<[email protected]> wrote in message
news:[email protected]...
>I just ran 10 miles in 85' with humidity at 74%, and I lost 1lb. When I
> hear stories like "I lost 7lbs running today" I cringe. I mean that
> can't be healthy, and it leads me to believe you are overhydrated. I
> drank plenty all day yesterday, and this morning prior to my run, so I
> was well hydrated, and I sweat accordingly. But 7lbs? I think if you
> have 7lbs of water to sweat out, you have to be overhydrated.

I have to wonder as well - I've gone running in 100°/95% for 80" with
one good water break, and never showed more than 1lb weight loss. Every
time I try to weigh in/out on a long workout (even when I get dehydrated by
the end of the run) I get virtually no weight loss. So 7lb would scare me.

Dave

"Tom B." <[email protected]> wrote:

>Comments, anyone? (Dan? Donovan?)

I'm even later than Sam sorry.

I wouldn't count the water part of the glycogen. It gets released but not
lost as such.

FWIW, I weighed myself before yesterday's run. Fully clothed, with waist
belt and a full 800ml drinking bottle. Did same when I'd finished after 1:15
at 70% HRmax and had lost 1.7kg => 2.5kg of water + CO2 out, 800g isotonic
sports drink in.