A X I M U M H Y D R A T I O N
Now that it's almost summer, hot weather means that all firefighters
and emergency medical field forces must pay closer attention to
the potential dangers of physical stress and overheating. When temperatures
exceed 90 degrees, or on hot humid days, it is especially important
to keep hydrated. As explained in the article which follows, drinking
plenty of liquids before, during and after a call or run is the
first step to staying fit.
One effective way to delay the onset of the detrimental effects
of dehydration is by increasing your total body water and blood
plasma volumes. Described below are four simple ways to significantly
increase your capacity to carry water.
Recent studies show that by engaging in almost any type of physical
exercise on a regular basis you will realize, in very short order,
as much as a 10-12% increase in your circulating blood plasma volume.
Current research also indicates that with continued training, especially
aerobic type training, their results ian increase in the efficiency,
the effectiveness, and the working capacity of the body's cooling
mechanisms, especially the sweat mechanism.
As a direct effect of training, the well tuned Firefighter/EMT/Paramedic
will carry more water, sweat less while achieving greater cooling,
and lose less salt via sweat enabling him or her to rehydrate more
quickly, and completely.
Carbohydrate is the Performance Fuel for Firefighters, EMTs and
Paramedics. This Foodstuff Fuel provides firefighters, emts and
paramedics with energy to work, and the water to sweat. By consuming
a diet that is rich (60%) in carbohydrates, fruits, vegetables,
breads, cereals, grains, rice and pasta, you can increase your capacity
to store carbohydrate by over 100%, and right along with it, significantly
more water. Additionally, most fruits, and vegetables contain large
amounts of water (up to 96%), and therefore, represent an excellent
source of both fuel, and water to enhance performance, and facilitate
Decreased Body Fat
Muscle tissue contains about 75% water, and fat cells contain less
than 25% water. Consequently, the less lard, and more lean mean
muscle tissue that you feature, the greater your percentage or,
volume of water.
Fat also acts as a tremendous insulator, and excess fat imposes
an absolutely useless additional burden upon your body. The consequences
of an increase percentage of body fat are a less efficient cooling
mechanism, and an increased absolute workload. The results are an
increased risk of injury, and an elevated rate of fatigue.
The adage that has been applied to athletics for generations is
that, "if you want to perform in the heat, then you better
train in the heat." The physiological basis for this old coaching
tip is that by subjecting your body to an increase heat load, especially
by working, or exercising in a heated, or hot and humid environment,
that your body will adapt; increasing blood plasma volume, and improving
the efficiency of your cooling mechanisms, especially the sweat
The benefits to be reaped from acclimatizing to heat are very similar
to those obtained through training. In fact, the most dramatic improvements
are realized in those humans that combine the two; exercising in
the heat. However, before you begin exercising in the heat, you
should first consult the F.D.N.Y. Health and Fitness Unit at 1-212-860-9252
for guidelines on training safely, and intelligently in heated environments.
The constant replacement of bodily water lost via sweat, and respiration
is absolutely essential for the maintenance of circulating blood
plasma volume, physiologic function, health, and performance. Generally,
this is an easy task for the hydration-conscious firefighter, emt
and paramedic, however, while in the performance of duty there are
frequently times when continued, or, immediate rehydration is impossible.
While operating at fires, emergencies, extended operations, or even
when confined within an apparatus while responding to a series of
alarms, firefighters, emts and paramedics are not afforded the opportunity
to rehydrate themselves, yet, current research shows that they can
lose bodily water at rates that exceed 2.5 quarts per hour! Marked
dehydration can result, and for reasons of personal health, and
safety must be remedied as soon as physically possible. Listed,
and described below is the "DOSs", and "DON'Ts"
of Rapid Rehydration designed to enable you to replace lost fluids
as quickly, and safely as possible.
- Drink Cold Fluids
The colder the better down to about 40 degrees F.
- Drink Dilute Beverages
Most common beverages, and some so-called "replacement fluids"
contain much too high a concentration of sugar, or, some other
nutrient to move swiftly from your stomach to the primary site
of absorption in the small intestine. You can facilitate the process
by diluting your chosen beverage with water. Ideally, your replacement
fluid should contain less than about 8% glucose, sucrose, or glucose
polymer, and a small measure of salt, (about 1/3 teaspoon of table
salt; sodium chloride, per quart of fluid).
- Drink Until Nearly Full
At your first opportunity, you should fill your stomach to about
75-80% of capacity by drinking approximately 20-or-so ounces of
your chosen replacement fluid.
- Continue Drinking
After initially filling your stomach to the point of being nearly
full, you should supplement your initial intake by consuming an
additional 6-8 ounces every 10-15 minutes. All totaled, during
periods of exposure to heat stress, and while in recovery, your
should ingest of at least between 1-2 quarts of fluid per hour.
- Move About
The mechanics of moving about casually while in the period of
recovery may actually facilitate the movement of fluid, and enhance
the rate of rehydration.
- Do Not Drink Hot Beverages
- Do Not Drink Concentrated Beverages
Fluids that contain relatively high concentrations of sugar, starch,
protein, or fat tend to sit in your stomach, and retard the process
- Do Not Consume Solid Food
Especially hot, solid food.
- Do Not Continue Working at a High Relative Intensity
Working at intensities that exceed 75% of your maximum aerobic
ability will retard the passage, and absorption of ingested fluids,
slowing the rehydrative process.
- Do Not Consume Beverages Which Contain Either Caffeine
Alcohol, and caffeine are two drugs that work decidedly against
you. The consumption of caffeine, or alcohol via food, drink,
or drugs (prescription, or non-prescription), will contribute
towards Dehydrating you as opposed to Rehydrating you!
- Do Not Rehydrate in the Vicinity of the Fire/Emergency
If possible you should rehydrate and recover in an environment
that is devoid of direct sun, heat, smoke, loud noise, and excessive
HOW TO MONITOR YOUR HYDRATION LEVEL
Because even a seemingly minor drop in bodily hydration level can
have a rather dramatic impact on your perception of effort, cardiovascular
function, ability to dissipate heat, and physical work capacity,
it is recommended that you monitor your hydration level frequently.
Described below are two methods with which you may evaluate your
hydration level daily.
- The "ABC's" of Morning Maintenance
a. Pass Water
b. Weigh Yourself
Probably the easiest way to monitor your daily state of hydration
is by weighing yourself. As described above, each morning you
should get up, pass water, weigh yourself, and then rehydrate
as need be. You will obtain the most reliable readings if you
follow this routine, starting first thing each morning, using
the same scale, and wearing approximately the same amount of clothing.
If upon weighing yourself you notice that you have dropped 2,3
or 4 pounds compared to your last few weigh-ins, remember, that
a 200 pound firefighter, emt or paramedic doesn't burn a full
pound of fat running the NYC Marathon, so, in spite of your best
wishes, the weight that you have lost is much more likely an indication
of water loss (dehydration), than anything else. For each pound
of water weight lost, you need to consume approximately sixteen
ounces (2-8 ounce cups, or, one 16 ounce pint) of either water,
or some other suitable replacement fluid.
- Maintenance Check for the PM Period
During the day, or throughout your tour of duty, evaluation of
hydration level by weight is less reliable because body weight
can fluctuate independent of hydration level due to meals, and
other variables. Evaluation of hydration level via the thirst
mechanism is also inappropriate, because in most cases you do
not develop the sensation of thirst until you are already significantly
The best bet is to start the day well hydrated; employing the
"AM ABC's", and then continue to take
in fluids via beverages, fruits, and vegetables throughout the
day. Then if you steer clear of, or minimize your intake of alcohol,
and caffeine, you can be reasonably assured of an adequate level
of hydration provided you continue to pass water on a regular
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Dr. Kerry Kelly
Chief Medical Officer
Dr. David Prezant
Chief Medical Officer
Director, FDNY CSU
Mary T. McLaughlin
Director, FDNY BHS