Everyone knows it is important to rehydrate if sweating profusely
after strenuous activity. However, determining the amount
of fluid intake necessary to offset this fluid loss can be
It is important to note that cool fluids are more beneficial
than warm fluids when rehydrating. There is no data available
to support the fact that cool fluid intake while exercising
causes intense stomach cramping.
If fluid loss has accelerated to the point of heat illness,
I.V. fluid replacement is the treatment of choice. However
in wilderness settings, that is not always possible.
Please note: Potassium intake should NOT be started
until serum electrolyte levels are available. This is important
because many commercial drinks being marketed today do contain
potassium; it vitally important to understand how your body
is affected by what you are put into it. Remember: As indicated
by Dr. Auerbach, YOU CANNOT RELY ON THE THIRST MECHANISM TO
Many times, the thirst mechanism does not work as efficiently
as we might think. After strenuous activity, there should
be mandatory scheduled breaks every 20-30 minutes including
fluid intake. If done routinely, we’d have fewer deaths
on the athletic field due to heat stroke/illness resulting
Fluid replacement beverages
With the emphasis on physical fitness in the United States,
targeting an overweight population, commercial drinks have
become extremely popular, with companies vying for greater
commercial time to increase their sales. There is much confusion
regarding the great variety of drinks being marketed. Which
are better for fluid replacement? Is it better to replace
electrolytes or increase carbohydrates? Is one of greater
importance than the other? Without getting into the major
physiologic details when comparing the gastric absorption
of carbohydrates and electrolytes, per the 1996 American College
of Sports Medicine’s guideline for replacing carbohydrates,
carbohydrates should be ingested at the rate of 30-60 grams/hour
to maintain oxidation. To my knowledge, this guideline has
not been challenged.
Sports drinks should contain about 5-10% of carbohydrates
in the form of glucose or sucrose to enhance endurance. Many
athletes suffer from cramps, nausea and diarrhea after drinking
10% glucose solution, per Dr. Auerbach. Research studies across
the board indicate that when engaging in prolonged, strenuous
activity, there should be fluid intake every 15-20 minutes,
or approximately one quart/hour.
Drinking carbohydrates during prolonged exercise may enhance
the performance of athletes. As per Dr. Auerbach, carbohydrate
containing beverages SHOULD NOT be placed into canteens, or
metal containers since microbial contamination would be inevitable.
In closing, clearly everyone knows that we need to replace
our fluids during prolonged exercise.
- Don’t rely on your thirst mechanism to alert you
to your need for rehydration. Rehydrate every 15-20 minutes
whether you want to or not.
- There are not a lot of differences between sports drinks
for rehydration purposes.
- You do not need to replace potassium to any great extent.
- You want to hydrate at about one quart/hour during heavy
exercise. Obviously one must take into consideration environmental
conditions such as heat and humidity, and your endurance
level, including body’s ability to acclimate.
- Know the differences between dehydrations symptoms, heat
stroke symptoms, heat exhaustion symptoms and hyponatremia
- In the outdoors, if you observe anyone experiencing mental
confusion, this should be considered a medical emergency,
with heat stroke the mostly likely cause.
- In moderate to severe dehydration, when replacing fluids,
drinking large amounts of fluids and gulping frequently
leads to extreme nausea and emesis (vomiting). You can still
rehydrate, yet avoid potential vomiting, even in children,
by taking in frequent, but very small amounts of fluid.
Even if it is a tablespoon of fluids every 15 minutes, this
will decrease the load on the gut, and decrease the nausea/vomiting
For further details on direct physiology of dehydration,
rehydration and fluid replacement, please review Wilderness
Medicine by Auerbach, which is a great reference.