Fluid RetentionRegulation

1
Fluid Retention/Regulation

• Pages
• 275-279

2
Water Loss in HeatDehydration

• Dehydration is an imbalance in fluid dynamics
  when fluid intake does not replenish water loss
• No matter what type of exercise there is always
  water lost
• Even non-exercise induced water loss also occurs,
  such as when power athletes attempt to make
  weight through rapid weight loss induced by
  common dehydration techniques, such as a sauna or
  steam room.
• The risk of heat illness increases when a person
  begins exercising in a dehydrated state.

3
Magnitude of Fluid Loss

• In an acclimatized person, water loss by sweating
  averages nearly 12 liters (26 lbs) on a daily
  basis
• Several hours of exercise can cause the sweat
  glands to become fatigued, which can in turn,
  impair core temperature.
• Marathon runners lose about 5 liters of fluid
  during competition, which accounts for 6-10 of
  body mass
• Wrestlers usually compete in a dehydrated state
  in order to make their weight

4
Consequences of Fluid Loss

• Just about any degree of dehydration impairs
  physiologic function and thermoregulation.
• As dehydration progresses and plasma volume
  decreases, peripheal blood flow and sweating rate
  diminish and thermoregulation becomes difficult
• Increased Heart rate
• Decreased blood flow to the skin
• Reduction in circulatory and temperature-regulatin
  g capacity to meet metabolic and thermal demands
  of exercise.

5
Fluid Loss in Winter

• Colder air contains less moisture, thus there is
  a greater fluid volume leaving the respiratory
  passages as incoming air becomes humidified and
  warmed to body temp.
• Causes up to 1 liter of fluid loss
• Cold stress stimulates an increase in urine
  production.
• Some people overdress

6
Diuretic Use

• Plasma provides a greater percentage of water
  loss from diuretic-induced dehydration
• Diuretic drugs can also impair neuromuscular
  function
• Vomiting and diarrhea are not good ways to make
  weight because they produce dehydration and
  cause excessive mineral loss.

7
Rehydration

• Adequate fluid replacement sustains the
  exceptional potential fro evaporative cooling of
  acclimatized humans
• Athletes/people should properly schedule fluid
  replacement to maintain plasma volume so that
  circulation and sweating progress at optimal
  levels
• Drinking water can increase blood flow to the
  skin for more effective cooling
• This prevents dehydration and its associated
  consequences

8
Rehydration

• For wrestlers, dehydration is a way of life so
  they can compete at a lower weight. This is also
  seen in ballet dancers
• A well-hydrated athlete always functions at a
  higher physiologic and performance level than a
  dehydrated one

9
Pre-Exercise Hydration

• Drinking extra water before exercising in a hot
  environment provides some protection against heat
  stress because it delays dehydration, increases
  sweating during exercise, and minimizes use in
  core temp.
• Recommended consumption is between 400 and 600 mL
  (13-20 oz) of cool water 20 minutes before
  exercise in heat.
• This increases stomach volume, but does not
  replace fluid uptake during exercise

10
Adequacy of Rehydration

• Changes in body weight indicate the extent of
  water loss during exercise and the adequacy of
  rehydration during and after exercise or athletic
  competition.
• Dark yellow urine with strong odor indicates
  inadequate hydration.
• Each lb of weight loss after exercise represents
  450 mL (15 fl oz).
• Water must be available during practice and
  competition.

11
Sodium Facilitates Rehydration

• A small amount of sodium added to a rehydration
  beverage facilitates more complete rehydration
  than plain water
• Restoring water and electrolyte balance in
  recovery occurs by
• Adding moderate to high amounts of sodium to the
  drink
• Combining solid food with plain water

12
Sodium Facilitates Rehydration

• Because the kidneys continually form urine, the
  volume of ingested fluid following exercise must
  be larger (usually by 25-50) than exercise sweat
  loss to restore balance.
• If too much sodium, the excess fluid intake
  merely increases urine output with no benefit to
  rehydration.
• With prolonged exercise in heat, sweat loss can
  deplete the body of 13-17 g of salt per day.
• A glass of OJ or tomato juice replaces almost all
  the potassium, calcium, and magnesium excreted in
  about 3 liters of sweat.