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Hydration
Kent Clark RD
February 11, 2005
Objectives
• Discuss consequences of dehydration
• Fluid needs
– Before, During & After Exercise
• Fluid Choices
Research
• Recommendations for daily intake of fluids, nutrients,
vitamins, minerals, etc., differ for athletes compared to
sedentary adults.
• Thirst is a very poor indicator of fluid needs during
physical activity.
• The volume of fluid that athletes consume during and
especially after exercise should be based on what they
lose in sweat.
• Athletes can lose large amounts of sodium in their
sweat. Unless a health professional recommends
otherwise, athletes should liberally salt their food, favor
sports drinks and include healthy high-sodium foods (i.e.,
pretzels, chicken noodle soup, etc.) in their diets.
Fluids
• Daily fluid requirements fluctuate greatly for people in hot
climates and for those who are physically active.
Dehydration resulting from the failure to adequately
replace fluids during exercise can lead to impaired heat
dissipation, elevated body core temperature and
increased strain on the cardiovascular system.
• Behavior, not thirst, is primarily responsible for
determining fluid intake. That’s because people typically
drink when they’re eating, passing a water fountain or
refrigerator and whenever they find fluids readily
available, such as at meetings or parties.
Water
• A 150 pound person has ~10-12 gallons of water
in their body.
• In Blood
– Transports glucose & oxygen to working muscles and
carries away carbon dioxide and lactic acid.
• In Sweat
– Dissipates heat through the skin to regulate body
temperature.
• Lubricates joints and cushions organs and
tissues throughout the body.
Fluids
• Dehydration affects the body in a variety of ways
due to loss of water weight, fluids, and
electrolytes as the body’s cooling system
becomes compromised:
– decreased work capacity with increased body
temperature @ 1% loss of body weight.
– dry mouth, reduction in urinary output, & decrease in
performance @ 3% loss of body weight.
– serious problems such as heat cramps, chills, nausea
and ~25% reduction in endurance @ 5% loss of body
weight.
Fluids
• Amount of fluids
– maintenance-usually 8-12 cups/day depending on
activity level & body size.
PLUS:
– pre-exercise – drink 12-20 oz, 2-3 hours before.
– during exercise- drink 6-10 oz every 15-20 minutes.
– post-exercise-16-24 oz for every lb. lost
• Types of fluids; usually want caffeine-free.
• Don’t Drink Excessive Amounts of Water
Hyponatremia (water intoxication)
• Low blood sodium levels which are caused
by losing sodium through sweat and
drinking too much water.
• Consume beverages with sodium in them
(sports drinks) during longer workouts in
warm conditions.
• Don’t restrict sodium containing foods
unless you have high blood pressure.
Environmental Conditions
• Heat & Humidity
– Risks for heat injury increase dramatically in hot,
humid environments.
– Evaporation may be compromised and you don’t
achieve the cooling affect of sweating.
• Cold
– Dehydration risk is reduced but not uncommon.
• Respiratory fluid losses
• Insulated clothing
• Decreased amounts of cold fluids ingested
Fluid Choices
•
•
•
•
•
Water
Juice
Milk
Sports Drinks
Smoothies
• Remember, many fruits
& vegetables are 8595% water.
• Lemonade
• Coffee or Tea
– Decaf is best
• Seltzer
• Soft Drinks
• Soups
• Water & Sports Drinks
are the fluids best
tolerated during
exercise.
Fluid Choices
• Remember that you can consume fluids
which contain carbohydrates to help
meet your carbohydrate needs during
exercise and for recovery after your
workout.
2 hours before
During
2 hours after
Types of Fluid
Amounts per Fluid
(ounces)
Total Fluids Consumed
(ounces)
Water
Snapple
Water
Sports
Drink
Sports
Drink
Milk
12 oz
20 oz
20 oz
8 oz
32 oz
12 oz
28 oz
16 oz
28 oz