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 85-95% 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.

Types of Fluid Amounts per Fluid (ounces)

Total Fluids Consumed (ounces)

2 hours before Water 12 oz 32 oz

Snapple 20 ozDuring Water 20 oz 28 oz

Sports Drink

8 oz

2 hours after Sports Drink

12 oz 28 oz

Milk 16 oz