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| Staying
Hydrated |
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Is it necessary for athletes
to drink fluids during exercise, or will this fluid cause the
athlete to "drag," that is, not to perform as well ? Restricting
fluids during exercise could actually cause a DECREASE in the
athlete's performance, and could cause serious medical problems
to an athlete. Some investigators have found that having the
athlete drink fluids before exercise and during exercise can
actually IMPROVE the athletes performance.
Fluid replacement is very important for athletes. An eighteen
year old who is not vigorously exercising needs approximately
2.5 quarts of replacement water every day. This is needed to
replace water excreted via urine (1.3 quarts), the skin (0.85
quart by perspiration), and the lungs (0.35 quarts by exhaled
air). To replace this water, the average individual consumes a
minimum of 1.2 quarts (38 ounces or five glasses) of fluid each
day, and an additional 1.0 quarts in foods, such as fruits and
vegetables, which contain large amounts of water. In addition,
0.3 quarts of water is formed when food molecules are degraded
for energy. With vigorous exercise, there will be an increase in
the loss of fluid from the skin (from up to 3.0 to 5.0 quarts)
and from the lungs (up to 0.7 quarts). This increased loss of
water will make the player dehydrated unless replaced; the
athlete needs to drink several quarts of water to
prevent dehydration.
During exercise, the body works hard at performing, which
produces a large amount of heat
internally. The core temperature of the body rises, and there is
a need for the body to
dissipate this additional heat. The major way that the body
handles this additional heat is by
sweating and evaporation of perspiration from the skin. Also,
players lose additional water
during exercise from exhaled air in the lungs. The body can
react unfavorably to fluid lose. An
athlete can experience early muscle fatigue, loss of
coordination, irritability, and a
inability to perform at an appropriate level if he/she becomes
dehydrated.
How, when, and with what should this water be replaced ?
The thirst mechanism is triggered by an abnormally high
concentration of salt (sodium) in the
blood, which can result when you sweat. As you sweat, you lose
water from the blood. The
remaining blood becomes more concentrated and has a high salt
(sodium) level. This triggers the
thirst mechanism and increases your desire to drink. To quench
your thirst, you drink water and
other fluids to decrease the blood concentration of salt
(sodium). However, this thirst
mechanism does not always work early enough for athletes
undergoing strenuous exercise. If an
athlete waits until the thirst mechanism kicks in, the player is
probably already dehydrated.
Water replacement should start before the game or practice,
continued during the activity, and
include post activity hydration.
Plain water, preferably cold, is the best fluid replacement.
Cold water leaves the stomach
faster than warm water, and will decrease bloating. Plain water
leaves the stomach much faster
than drinks containing glucose (sugar), such as Coca Cola,
Pepsi, Gatorade or Exceed. The
purpose of hydration in sports is to get water to the working
muscles and cells as soon as
possible.
During exercise lasting less than ninety minutes, there is no
evidence that a
carbohydrate-electrolyte drink (such as Gatorade) is any better
than plain water.
In addition to the fact that sugared drinks leave the stomach
slower than plain water, players
should avoid highly sugared drinks (greater than 5% glucose) and
chocolate bars within one hour
of a game or practice for another reason. This sugar load will
cause the body to secrete a
hormone (insulin) that will actually cause a decrease in the
blood level of carbohydrate about
thirty to forty minutes after the ingestion of the sugar. This
decrease in the blood level of
carbohydrate can cause the players to experience a sluggish
feeling when they step out on the
playing field or ice surface.
Water is a must during games and practices.
Drinking water before a game or practice, even cold water, will
not cause cramps. In fact,
there is a good possibility that cramps can result from
dehydration due to drinking to little
water.
The American College of Sports Medicine recommends drinking
about two glasses (17 ounces) of fluid two hours before the scheduled game or practice. During
exercise, athletes should start
drinking early and at regular intervals in an attempt to consume
fluids at a rate sufficient to
replace the water lost through sweating and exhaled air. In a
practice this could be two to
four ounces (a half glass) of water every five to ten minutes,
or, in an ice hockey game, two
to four ounces every shift.
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