Hydration for the Distance Runner
by John
Steitz, MCP Coach
Without proper
hydration, you have no hope of completing a marathon. You need to watch your Hydration before,
during and after ever training run (and on race day!)
If you remember nothing else from this clinic, remember that Hydration is a BALANCE, that even a *little* dehydration can cause a lot of problems, and that Hydration Begins at Home!
Both Dehydration and Hyponeutremia are serious problems for distance runners, caused by the body’s hydration being seriously out of balance.
Dehydration (not enough water in your system) is a medical condition with serious or fatal consequences: reduced physical capacity and heat tolerance, deterioration in cognitive function, failure of thermoregulation, physical incapacity, and ultimately, organ failure. Even mild dehydration, if repeated over and over again, can lead to renal stones, urinary infections, severe constipation, rectal afflictions, and cutaneous membrane drying.
Progressive symptoms of Dehydration include increased thirst, decreased urine output, concentrated urine and/or urine that is deeply yellow or amber in color, dry mouth and swollen tongue, the inability to sweat, weakness, confusion, dizziness, sluggishness, fainting, and palpitations (feeling that the heart is jumping or pounding). If you ever notice a runner with two or more of these latter symptoms, please summon assistance for that runner from a coach or race official.
Mild Dehydration can be treated on the scene, with shade, rest, and having the victim drink small, but frequent small amounts of fluids. Moderate to Severe Dehydration requires medical attention, because treatment may require IV fluids and/or hospitalization. Moderate to severe dehydration may be combined with other conditions requiring medical attention, e.g., Heat Stroke. When in doubt, get the runner off the trail and onto the ground, and call for medical assistance.
The opposite of Dehydration is Hyponeutremia (too much water in your system), a medical condition with serious or fatal consequences. Hyponeutremia (or “water intoxication”) comes from ingesting water (only) for a period of time, but sweating out both water *and* electrolytes [sodium (Na+), potassium (K+), chloride (Cl-), calcium (Ca2+) , magnesium (Mg2+) , bicarbonate (HCO3-), phosphate (PO42-) and sulfate (SO42-)]. Full-blown Hyponeutremia is very rare, but it has been seen in slower runners, who take several 4+ hours to complete a marathon, and who ingest nothing but water during their run. The Marine Corps Marathon has had one fatality from Hyponeutremia.
Progressive symptoms of Hyponeutremia include fatigue, lightheadedness, weakness, cramping,
weight gain, nausea, boating and/or swelling, dizziness, headache, confusion,
fainting, disorientation, seizures (severe cases) and coma (severe cases). Notice
how some of these symptoms appear the same as those for Dehydration! Unless a runner can *clearly* communicate
symptoms, Hyponeutremia can look like Dehydration, and vice versa. When a runner is confused or disoriented (or
worse), seek professional medical attention – do not attempt treatment unless
you are a medical or first aid provider.
The medical assistance
required to treat Hyponeutremia can include fluid
restriction and/or diuretic therapy. Cf.: http://www.ace.cc/Critical%20Care%20Topics/electrolyte_disturbances.htm
Mild Hyponeutremia
(e.g. cramps) is often miss-diagnosed.
If you, yourself, ever have *severe* cramps, seek medical assistance
immediately.
Hyponeutremia is
better prevented than treated. To avoid
it, replace the fluids you lose through sweat while running – and no more. Drink small amounts frequently, rather than
large amounts all at once. Consume salty
foods and beverages before, during and after the run. And determine *your own* fluid needs during a
run through body weight monitoring.
Thirst is a highly
INACCURATE indicator of how much fluids you body needs at any given time. Lack of thirst does *NOT* mean that you are
fully hydrated……..or properly hydrated.
To find the actual
amount of water you need each day – without running, just your body’s normal
requirement for living - , divide your weight by 16. (You actually take half
your weight and divide it by eight—the number of ounces in a glass.) So, a
115-pound person needs to drink 7.2 8-ounce glasses of water a day, 180-pounder
needs 11.25, and a 225-pounder needs 14.
To this base number,
consider the effects of: heat, humidity, diet, medications, and bleeding/menstruation. Each of these may increase your daily fluid
requirements – on top of what your body needs for vigorous exercise over
extended periods of time.
[Humidity is an
especially nasty factor in hydration.
The cooling effect you gain from sweating comes not from the release of
sweat, but by from the *evaporation* of that sweat off of your skin. That is why technical shirts with wicking
fabric spread out your sweat all over the place, to increase the surface area
of that sweat, and increase the amount that evaporates.
But with high
humidity in the air around you, there is no place for the evaporation to go –
the air is already saturated with vaporized water molecules. You sweat, and sweat, and sweat, and
sweat……and nothing happens! You remain
overheated and covered with sweat, but *now* you’re dehydrated, too!]
To figure out how
much water you lose *while running,* one easy way is to measure your weight
both before and after the run. Subtract
your end weight from your starting weight, to determine your net loss of
weight, in pounds. Most, if not all, of
this weight lose is loss of fluids during the run.
Each 8.35 pounds of
lost weight corresponds to loss of a gallon of fluid during the run. If you drank fluids during your run, you
need to add that amount to your loss, as your real lose was even greater,
modified only by the fluids you consumed.
Say, you started out
with 180 lbs before the run, and were 3 pounds lighter at the end:
Starting weight in lbs. 180
- Ending weight in lbs. 177
Net weight loss:
3 lbs.
Pounds/8.35 = gallons of fluid .35
gal.
+ Fluid
consumed .25 gal
=
Gross fluid loss:
.60 gal!
The consequences of
fluid loss are often expressed as a percentage of one’s total fluid content,
which is a function of one’s gender and body weight. Water makes up about 60 percent of a man’s
weight and 50 percent of a woman’s. So
a 180 lb man might have a base on 108 lbs of water, while a 150 lb woman might
have a base of 75 lbs. of water. In
doing the math, convert all fluid quantities to pounds, to make the arithmetic
easier.
In the case above,
the gross fluid loss during the run was .60 gallons, but the net loss was only
.35 gallons, because the runner drank .25 gallons (a quart, or, roughly, a
liter) during the run. .60 gallons of
fluid corresponds to 5.01 pounds lost, while .35 gallons equates to only 2.92
lbs.
For runners of
varying weights, a loss of 5 pounds corresponds to a percentage of body weight
as follows:
100 lbs – 5%
120 lbs – 4.2%
150 lbs – 3.4%
180 lbs - 2.8%
Compare this to a
loss of only 2.92 pounds of fluids during the run:
100 lbs – 2.9%
120 lbs – 2.4%
150 lbs – 1.9%
180 lbs - 1.6%
In the example
above, only the 150 and 180 pound runners kept their fluid loss below 2%, and
even then, only when they consumed a quart of fluids (32 ounces) during the
run.
And that’s
significant, because as little as 2% dehydration can have measurable effects on
performance, like a 7% decrease in endurance. Lack of water in the system
thickens blood in arteries and veins.
Thicker blood doesn’t move as fast, so its ability to transport oxygen and
glycogen (carbohydrate fuel) to working muscles is compromised. So too, is the bloodstream’s ability to
remove lactic acid and CO2 from those muscles.
A dehydrated bloodstream provides less lubrication to muscles, making
them more prone to injury. And the
collapse of good form from muscles prematurely fatigued from dehydration can
compound chances for injury in the latter stages of the run.
To avoid these
consequences, you need to ingest *some* fluids during your run – not too much
(as we’ll discuss below), but up to 33 ounces an hour.
The best way to
ingest fluids (and food) during a run is in small quantities spread throughout
that run. For those practicing the
walk/run (“
On race day, take a
half-cup of fluids at every aid station, preferably the sport beverage that is
adding some sodium and potassium that plain water just doesn’t have.
But slower runners
may not be able to wait to drink at water stations. If water stations are 2 miles apart (as at
MCM), they are encountered every 14
minutes for 7 minute per mile pace, every 20 minutes for 10 minute per mile
pace, and only every 28 minutes for 14 minute per mile pace. Assuming each runner gets about 5 ounces of
fluid at each water station, the seven-minute-miler gets 20 ounces an hour, the
ten-minute-miler gets about 15 ounces, and the fourteen-minute-miler gets only
10 ounces per hour –far short of their theoretical 33 ounces per hour that
their digestion can handle, and perhaps far short of the fluids that are losing
each hour.
And whatever your
pace, you have to practice taking fluids during your training runs, if you’re
going to be able to do it without screwing up your digestion on race day.
There are many
popular bottle-holders and belts that let you carry extra fluids and spread the
weight out evenly around your waist.
Some runners find that the backpack bladder devices (Camel pack,
Hydrapak, et al.) offer a better option, because you carry the weight in your
shoulders and upper back, rather than your waist and lower back.
If you hate to carry
the weight, consider hiding a bottle along the course of your training
run. Or at a race, enlist your
spectators as support personnel, and give them bottles of fluids to hand off to
you at specific points along the course.
And don’t forget –
you need to replace electrolytes as well as water during your run. For sports beverages – READ the LABEL. The products vary widely in the amount of
sodium and other electrolytes, as well as simple carbs, they provide.
For example 8 ounce
servings of the following beverage provide:
Carbs (gram)
Calories (kcals) Sodium (mg) Potassium (mg)
Water 0 0 0 0
Orange Juice 26 112 3 496
Gatorade 14 50 110 30
Gatorade Endurance 14 50 200 30
Powerade 19 70 55 30
Electrolytes can also
be replaced with salty foods or sodium pills marketed at running stores.
As with anything
else in your training, first try a new hydration device, or a fluid-ingestion
plan, on your mid-week short runs. If it
works there, try it on a few long runs.
If it works on the long runs, then, and only then, should you use it on
race day.
So ingesting fluids
during a race……or a long run…….is a very, very good idea. But can you ingest enough fluids during a run
to compensate for all the fluids you lose?
Probably not.
No matter how much
you drink, your stomach and digestive tract can only absorb about 1 liter – 33
or 34 ounces – per hour – and that’s under the best of conditions. Unabsorbed
fluids will either slosh around in your stomach, or worse, they will go
straight to your bowels, where they will pull salt from the body and dilute the
mineral balance in the tissues…which is the very definition of Hyponeutremia.
http://www.nfrmag.com/July-Aug%2005/Hyponeutremia.asp Even if you escape the more serious symptoms
of that condition, you may still be greeted with some really nasty cramps.
For that reason, you
really shouldn’t drink more fluids than you lose through sweat during a run and
UNDER NO CONDITIONS should you drink more than 33 ounces per hour, no matter
HOW much fluid you lose during a race or training run.
And even drinking 33
ounces an hour is a difficult trick for anybody running at more than 75% of
their maximum heart rate. Furthermore, during your run, your body will be less
able to absorb water, electrolytes and nutrients than normal, because of blood
flow away from the stomach toward working muscles.
So no matter how
great your personal system for hydration-during-the-run, assume as a matter of
caution, that you will almost always lose more fluids during a long training
run or race in the heat and humidity of DC than you can replace by drinking
during that run. What to do?
Well, that’s my
final point: Hydration Begins at Home!
If you come to the race or training run well-hydrated, you can still
lose more fluids than you replenish during that run, but not be in physical
distress from dehydration. And if you
come in well-hydrated, you need not worry about over-hydrating during the run
(more than 33 ounces per hour), because you can back off drinking a little
during the race, with fewer ill effects.
Yes, being
well-hydrated going into a race has its drawbacks. But you should rejoice every time you have to
urinate before or during a race or a training run, because that is a sign that
your hydration balance is at least middle-of-the-road, if not
well-saturated. [In my own 12
marathons, the only common denominator among my best times is the need for a
pit stop in the privy mid-course.]
Before a marathon or
long training run, I would counsel you to hydro-load the way you would
carbo-load. 2-3 days before the long
run, drink more fluids in small amounts throughout the day. 66% of what you ingest will be urinated away,
but 33% will remain in your body for the run.
For example, to gain
1/2 gallon (4.175 pounds) of extra fluids in your system prior to a long run,
you would need to ingest a total of 1.5 gallons in the two to three days prior
to the long run. Over three days, 1.5 gallon equals ½ gallon, or 64 ounces, per day. Because your body absorbs only about 1 liter
(33.81 ounces) per hour, you must drink small amounts over a period of time to
absorb extra fluids (over and above what you would drink normally). 64 ounces over 12 hours is 5.33 extra ounces
per hour – a little more than a half glass of fluid, or ¼ of a 20 ounce bottle
of a sports beverage.
Don’t take large
quantities of fluids at any one time, even if you’re not exercising. Large fluid quantities will slosh around in
your stomach or worse yet, bypass your digestion and go straight to your
bowels. [Hyponeutremia!] Large quantities of fluids without food
solids may also cause gastric distress.
And as you would
during the run, don’t just drink extra water before the run, lest you dilute
your electrolytes! Make sure your
electrolytes are topped off too, not just your H2O or carbs! Eat
salty pretzels, or your favorite salty snack, as you hydro-load before a
marathon or long run. Or, depending on
your normal diet, just eat normally (or carbo load!)
- the average American diet contains *plenty* of
sodium! Some runners drink sports
beverages (Gatorade, et al.) while wandering the expo or sitting in clinics the
day before a race. And bananas contain Potassium, an electrolyte that helps the
body retain sodium.
With a little extra
fluid each hour over the course of 2 to 3 days, you can build a good fluid
reserve prior to the race or long run.
Like all other aspects of marathon training, this is something you would
have to try, and perfect, prior to your Saturday training runs, before you ever
tried it prior to a race.
Make proper hydration before, during, and after your long runs a habit. You will perform better, and will *feel* better, with less risk of injury.