Fluids and Electrolytes: Hydration for Physical Activity...

Fluids and Electrolytes: Hydration for Physical Activity and Sport

Rookie Module

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Learning Objectives of the Course

After completing this module, participants will be able to answer the following questions How do athletes stay cool during exercise, particularly

in the heat? What is sweat?

– What is its role during exercise?

What is dehydration? – What are the concerns with it?

What are the risks from over heating? – What heat illnesses can occur during exercise?

• What are the signs?

• How are heat illnesses treated and best prevented?

What strategies promote safety and performance during exercise in the heat?

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How Do Athletes Stay Cool?

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Nadel ER, et al. Ann N Y Acad Sci. 1977;301:98-109. Wilmore JH, Costill DL, Kenney WL. Physiology of Sport and Exercise 4th edition. Champaign; Human Kinetics Publishers; 2008: pp 252-268.

Effect of Exercise

Increases

metabolism and

body heat

production

Response to Exercise:

Maintenance of

Homeostasis

Heat removal is required

Means of doing so include

• Conduction (Cd)

• Convection (Cv)

• Radiation (R)

• Evaporation

(E, via sweat)

Failure to stay cool can have dire health consequences

Cv

R

E

Cd

What Is Sweat?

A thin layer of fluid released on the skin surface Contains water and minerals (electrolytes) from body fluids

Produced by sweat glands when body temperature rises When sweat evaporates, it cools similarly to the effect of

rubbing alcohol on the finger of a hand that is waved

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Sweat Minerals Low - High, mg/8 oz sweat

Sodium 110 - 440

Chloride 170 - 511

Potassium 37 - 75

Calcium 0 - 28

Magnesium < 12

Costill DL. Ann N Y Acad Sci. 1977;301:160-174. Maughan RJ. J Sports Sci. 1991;9:117-142.

What Is the Role of Sweat During Exercise?

Over heating can cause fatigue and heat illness Sweat cools the body to help prevent these issues and to sustain

performance – Sweat must evaporate off the skin to cool

– Sweat that drips off onto the field or court does not cool the body

There are consequences – Continual loss of sweat without replacement leads to dehydration

– In most cases, dehydration will hurt performance

• Particularly if the exercise is done in the heat

– Dehydration beyond 2% of body weight puts the athlete at risk for heat illness

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Costill DL. Ann N Y Acad Sci. 1977;301:160-174. Cheuvront SN, et al. Cur Sports Med Rep. 2003;2(4):202-208.

What Is Dehydration?

A reduction in the normal, necessary amount of body water – Normally, muscle is ~ 73% water; blood is ~ 80% water

Losses affect body’s ability to function Examples of how dehydration occurs

– Excessive sweating

– Diarrhea or vomiting

– Water deprivation or inadequate replacement

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Murray B. J Am Coll Nutr. 2007;26(5):542S-548S. Cheuvront SN, et al. Cur Sports Med Rep. 2003;2(4):202-208.

Example of 3.7% Dehydration

Athlete weighs 135 lb before sports practice

After a 90-minute practice, athlete weighs 130 lb − Despite adequate access to water during practice

Acute weight change is 3.7% ([135 – 130]/135 x 100)

What Are the Concerns With Dehydration?

Impaired cardiovascular function1

– Symptoms

• Higher heart rate and rapid pulse, at rest or during exercise

• Drop in blood pressure

Impaired body cooling2

Feelings of fatigue and mood changes2,3

Starting at 2% dehydration,2-4

– Physical endurance is reduced

– Cognitive function is impaired

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1. Crandall CG, Gonzalez-Alonso J. Acta Physiol. 2010;199:407-423. 2. Murray B. J Am Coll Nutr. 2007;26(5):542S-548S. 3. Lieberman HR. J Am Coll Nutr. 2007;26(5):555S-561S. 4. Grandjean AC, et al. J Am Coll Nutr. 2007;26(5):549S-554S.

What Are the Risks From Over Heating?

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Rapid increase in core temperature

– Like a car that loses it radiator fluid, when the body loses sweat that is not replaced, it is as if …

• The car radiator has a leak (sweat loss)

• The heat transfer from the engine (muscles) to the radiator (skin) is impeded

• The car engine block over heats and the car breaks down

Heat illnesses are similar to the car breaking down – Heat cramps

– Heat syncope

– Heat exhaustion

– Heat stroke

Wilmore JH, Costill DL, Kenney WL. Physiology of Sport and Exercise 4th edition. Champaign; Human Kinetics Publishers; 2008: pp 252-268. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(3):556-572. Sawka MN, et al. Int J Sports Med. 1998;19(suppl 2):S108-S110.

Heat Cramps (Exercise-Associated Muscle Cramps)

Definition: uncontrollable tightening and spasms of skeletal muscle, linked with intensity of exercise in the heat

Symptoms

– Twitching or tightening precedes the cramp

– Fatigue

– Possibly nausea

Contributing factors

– Muscle fatigue

– Large losses of fluid and salt loss

– Prolonged competition or games within a day

Treatment

– Stretching

– Rest

– Replace fluids and electrolytes (orally or by intravenous infusion depending on severity)

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Wilmore JH, Costill DL, Kenney WL. Physiology of Sport and Exercise 4th edition. Champaign; Human Kinetics Publishers; 2008: pp 252-268. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(3):556-572.

Heat Syncope

Definition: low blood pressure and collapse in the heat, as a result of heat exposure, blood pooling, and lack of movement

Symptoms

– Loss of consciousness after standing or stopping movement in a hot environment

Contributing factors

– Excessive heat exposure, possibly while wearing excess clothing

– Not necessarily large fluid losses

Treatment

– Lay individual on back and elevate legs to restore blood flow to head

– Rest in a cool area to reduce body temperature

– Provide fluids to drink if dehydration appears to be a factor

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Heat Exhaustion

Definition: inability to continue work or exercise in the heat

Symptoms – Fatigue, weakness

– Irritability

– Headache

– Nausea or vomiting

– Chills

– Low blood pressure and rapid pulse

– Core temperature may be elevated, but rectal temperature is < 40° C

Contributing factors – Excessive sweat and electrolyte loss

– Prolonged exercise in heat

– Pre-existing dehydration

Treatment – Rest in cool area, elevate legs if victim feels faint

– Fluid and electrolyte replacement orally or intravenously

– Monitor vital signs

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Heat Stroke (HS)

Definition: extreme core body temperature increase due to failure of the brain to function normally and sustain cooling – Other organ systems also failing

Symptoms – Rectal temperature > 40° C is the definitive sign – May have hot pale skin – Confusion or irrational behavior – Hyperventilation (rapid breathing) – Vomiting – Loss of consciousness – Seizures – Coma

Contributing factors – Intense exercise in or exposure to the heat – Recent illness – Use of certain medications – Dehydration is likely, but not necessary

for HS to occur Treatment

– Immediate cooling such as in an ice bath or ice packs – Treat as a medical emergency—call 911

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Medications thought to increase

risk of heat stroke

• Diuretics

• Drugs having diuretic actions

- Ephedrine-containing medication

- Ephedra herb

- Alcohol

- Possibly caffeine and theophylline

How Do We Prevent Dehydration?

Thirst

– Loss of fluid affects our blood

• Becomes more salty, more concentrated

• Blood pressure drops

– Both effects are detected by cardiovascular system and brain to signal thirst

– Drinking started

Replacement of fluids by thirst is seldom perfect during exercise

– Thirst stops before enough fluid is consumed to replace fluid throughout the entire body

• However, saltiness of the blood is reduced to normal and blood pressure is restored

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Greenleaf JE. Med Sci Sports Exerc. 1992;24(6): 645-656.

What Strategies Promote Safety and Performance During Exercise in the Heat?

Estimate rate of sweat loss Anticipate volume needs

– Use guidelines for replacement1-4

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1. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390. 2. American Dietetic Association, Dietitians of Canada, American College of Sports Medicine. Med Sci Sports Exerc. 2009;41(3):709-731. 3. Burke LM, Hawley JA. Sports Med. 1997;24(1):38-54. 4. Maughan RJ, Shirreffs SM. Scand J Med Sci Sports. 2010;20(suppl 3):40-47.

How Do We Estimate Fluid Needs?

Weigh yourselfa

– Before exercise

– After exercise

Record duration of exercise in hours

Estimate fluid volume intake (16 oz = 1 lb)

– For adults, 1 “gulp” is ~1 ounce

– For children, 1 “gulp” is ~1/2 ounce

Account for urine loss, if relevant (8 oz = 0.5 lb)

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Difference = Δ body weight (BW) in pounds (lb)

a Method is relevant and precise for 1 to 2 hours of exercise. During longer events, depletion of carbohydrate may account for some of the change in body weight and is not associated with fluid loss. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390. American Academy of Pediatrics. Committee on Sports Medicine and Fitness. Pediatrics. 2000;106(1 pt 1):158-159. Maughan RJ, et al. J Sports Sci. 2007;25(7):797-804.

ΔBW + drink volume – urine volume = Sweat rate, lb/hour

Exercise duration, hour

How Do We Estimate Fluid Needs? (Metric)

Weigh yourselfa

– Before exercise

– After exercise

Record duration of exercise in hours

Estimate fluid volume consumed

– For adults, 1 “gulp” is ~28 mL

– For children, 1 “gulp” is ~14 mL

Account for urine loss, if relevant

– Use units of milliliters and divide by 1,000 for liters

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a Method is relevant and precise for 1 to 2 hours of exercise. During longer events, depletion of carbohydrate may account for some of the change in body weight and is not associated with fluid loss. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390. American Academy of Pediatrics. Committee on Sports Medicine and Fitness. Pediatrics. 2000;106(1 pt 1):158-159. Maughan RJ, et al. J Sports Sci. 2007;25(7):797-804.

ΔBW + drink volume – urine volume = Sweat rate, L/hour

Exercise duration, hour

Difference = Δ body weight (BW) in kilograms (kg)

Estimating Fluid Intake Needs During Exercise

Repeat procedure for estimating fluid intake in various weather conditions

Obtain estimates for – Hot and cooler days

– Different amounts of clothing

– Different intensities of exercise

Apply appropriate sweat rate to appropriate conditions during training and competition for intake estimate

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American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390.

Fluid Intake Guidelines: US Volumes

2007 ACSM Position Statement

Provides specifics on fluid formulation to optimize safety and performance

Recommends replacement during exercise

– Volume to prevent acute loss of > 2% of body weight

– Do not drink in excess

• No demonstrable benefits of over hydration

• Increases risk of hyponatremia

Recommended volume to ingest every 15 min to minimize dehydration

Expected sweat rate, lb/hour

oz/15 min to replace

80%


90%


100%

0.25 0.8 0.9 1.0

0.50 1.6 1.8 2.0

0.75 2.4 2.7 3.0

1.00 3.2 3.6 4.0

1.50 4.8 5.4 6.0

2.00 6.4a 7.2 8.0

3.00 9.6 10.8 12

4.00 12.8b 14.4 16.0 Abbreviations: lb, pound; oz, ounce. a At this rate, a 121-lb female experiences only 0.3% dehydration (< 1% body weight loss). b At this rate, a 154-lb male experiences only 0.5% dehydration (< 1% body weight loss).

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American College of Sports Medicine (ACSM). Med Sci Sports Exerc. 2007;39(2):377-390.

Fluid Intake Guidelines: Metric Volumes

2007 ACSM Position Statement

Provides specifics on fluid formulation to optimize safety and performance

Recommends replacement during exercise

– Volume to prevent acute loss of > 2% of body weight

– Do not drink in excess

• No demonstrable benefits of over hydration

• Increases risk of hyponatremia

Recommended volume to ingest every 15 min to minimize dehydration

Expected sweat rate, L/hr

mL/15 min to replace

80%


90%


100%

0.25 50 56 62

0.50 100 112 125

1.00 150a 169 188

1.50 200 225 250

1.75 300 338 375

2.00 400b 450 500

2.50 500 562 625

3.00 600 675 750 Abbreviations: L, liter; mL, milliliter. a At this rate, a 55-kg female would experience only 0.4% dehydration (<1% body weight loss). b At this rate, a 70-kg male would experience only 0.6% dehydration (<1% body weight loss).

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American College of Sports Medicine (ACSM). Med Sci Sports Exerc. 2007;39(2):377-390.

What Is Hyponatremia?

Risk Factors

• Over drinking, weight gain during exercise

• Small body mass

• ―Back-of-the-pack‖ runner

• Female

• Drinking fluids containing no sodium

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Excessively diluted sodium (salt) in the blood

Defined as

– Plasma blood sodium level, < 135 mmol/L

– Normal range, 136 to 142 mmol/L

Symptoms

– Headache

– Coma and/or death from shifts in water into brain cells

Treatment

– Diagnostic confirmation of low blood sodium levels

– Urgent medical emergency

• Hypertonic saline for acute blood sodium elevation

• Water restriction and/or diuretics to reduce fluid load

• No IV’s of hypotonic or isotonic saline

Maughan RJ, Leiper JB. Eur J Appl Physiol Occup Physiol. 1995;71(4):311-319. Montain SJ, et al. Br J Sports Med. 2006;40:98-106. Hew-Butler, T et al. Clin J Sport Med. 2005;15:208-213.

What Strategies Promote Safety and Performance During Exercise in the Heat?

Estimate rate of sweat loss Anticipate volume needs

– Use guidelines for replacement1-4

Make it easy to get to fluid – Sports bottles

– Sidelines

– Belts with bottles

– Time-outs/breaks for fluids

Use fluids that promote adequate volume intake and encourage drinking

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1. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390. 2. American Dietetic Association, Dietitians of Canada, American College of Sports Medicine. Med Sci Sports Exerc. 2009;41(3):709-731. 3. Burke LM, Hawley JA. Sports Med. 1997;24(1):38-54. 4. Maughan RJ, Shirreffs SM. Scand J Med Sci Sports. 2010;20(suppl 3):40-47.

What Are the Characteristics of Beverages Used During Exercise?

Encourage drinking to maintain hydration

– Lightly flavored

– Moderate sweetness

– Contain sodium (salt)

Help replace electrolytes that retain water in the body

– Contain electrolytes/minerals

– Sodium and chloride are most critical

Promote absorption of fluid and fuel

– Contain simple sugars such as glucose

• Relatively low amounts (less than that in fruit juice and regular soda)

Ability to sustain physical and mental performance during exercise

Recommended

Oral rehydration solutions

Sports drinks

Acceptable in some cases

Water

Not recommended

Energy drinks

Fruit juice

Soft drinks—diet or regular

22 Maughan R, Murray R (eds). Sports Drinks: Basic Science and Practical Aspects. Boca Raton; CRC Press; 2000: pp 45-88.

Limitations of Conventional Fluid Replacement Options

Issue Excessive salt loss

Indigestion/heart burn

Large sweat losses

Limitation Sports drinks with 100 to 110 mg sodium/8 oz

are on low end of that in human sweat (110 to 440 mg/8 oz of sweat)

Calorie content and presence of acidity may delay gastric emptying and provoke indigestion in those at risk

May be difficult to match volume ingested with sweat rate

– Particularly if sodium content is low and carbohydrate (CHO) is relatively high (ie, exceeds 60 g CHO ingested/hour—too many calories)

Athletes experiencing these issues should select rehydration solutions with

sodium content of > 660 mg/quart (> 30 mEq/L),

low CHO content of ~ 20 to 40 g/quart (20 to 40 g/L), and/or

possibly devoid of citric acid.

23 Maughan R, Murray R (eds). Sports Drinks: Basic Science and Practical Aspects. Boca Raton; CRC Press; 2000: pp 45-88.

Can Hydration Status Be Monitored?

Yes, by…

Monitoring change in body weight day by day

– Weigh in before and after each exercise session

– Attempt to restore at least 80% of weight lost from prior day workout

Noting the urine color or concentration

– Color is an indicator of hydration status

• Intense yellow, small volume indicates dehydration

• Clear, nearly colorless indicates normal hydration

Being aware of thirst – Alone, thirst is a poor indicator during exercise

– Combined with acute change in body weight and urine index, thirst is valid predictor

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American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390. American Dietetic Association, Dietitians of Canada, American College of Sports Medicine. Med Sci Sports Exerc. 2009;41(3):709-731. Burke LM, Hawley JA. Sports Med. 1997;24(1):38-54. Maughan RJ, Shirreffs SM. Scand J Med Sci Sports. 2010;20(suppl 3):40-47.

Restoring Hydration Between Training Bouts

When body weight is less than normal after training, dehydration has occurred

Athlete should attempt to restore weight before next practice

Replacement guidelines, particularly during 2-a-day sessions

– Drink 25% to 50% in excess of the amount lost1

– Compensate for urine production

– Additional sodium promotes fluid retention and rehydration

– Carbohydrate and high-quality protein in the beverage can help rehydration and rebuilding of muscle proteins2

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Example of Restoring Hydration

Athlete lost 3 lb during a morning athletic practice

Afternoon practice will occur 3 hours later

Athlete should replace 3 lb plus 0.75 to 1.5 lb during the next couple of hours to restore hydration − 3.75 to 4.5 lb total fluid

1. Casa DJ, et al. J Athl Train. 2000;35(2):212–224. 2. American Dietetic Association, Dietitians of Canada, American College of Sports Medicine. Med Sci Sports Exerc. 2009;41(3):709-731.

What Other Strategies Promote Safety and Performance During Exercise in the Heat?

Environmental awareness

Clothing adjustment

– Lightweight, reflects light

– Porous

– Retains fluid for evaporation

Modifications in training sessions – Location; out of the heat

– Time of day; cooler hours and less direct sunlight

Heat acclimation

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American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(2):377-390. American Dietetic Association, Dietitians of Canada, American College of Sports Medicine. Med Sci Sports Exerc. 2009;41(3):709-731. Burke LM, Hawley JA. Sports Med. 1997;24(1):38-54. Maughan RJ, Shirreffs SM. Scand J Med Sci Sports. 2010;20(suppl 3):40-47.

What Is Heat Acclimation?

Adaptation of the body to better tolerate exercise in the heat

Acquired within a 10- to 14-day period of training – ~100 minutes per exercise session

– Heat exposure

– Reduced training intensity to prevent heat stress

Benefits – Expanded total body water and blood volume

– Improved sweating response • More evenly across entire body

• Starts sooner, before body core temperature rises too high

• Higher rate of sweating

• Less electrolytes in the sweat (conservation of minerals in the body)

– Reduced core temperature • Blunted rate of rise in core temperature

– Less cardiovascular stress during training

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Wilmore JH, Costill DL, Kenney WL. Physiology of Sport and Exercise 4th edition. Champaign; Human Kinetics Publishers; 2008: pp 252-268.

Summary

Sweating and evaporation of sweat are the most important means by which athletes stay cool during exercise and athletics, particularly in the heat – Sweat consists of water and salts (electrolytes)

– Total amounts of water and salts lost are dependent on sweat rate

Heat cramps, heat exhaustion, and heat stroke are the 3 main risks of over heating during exercise – All 3 are related to intense exercise in the heat

– Key factors are dehydration and not tailoring the exercise session for heat

Dehydration is the loss of body fluid – At > 2% of body weight can result in reduced performance and risk of illness

Fluid intake needs should be estimated to replace sweat loss – Estimation should consider temperature, clothing, and exercise conditions

– Hydration status should be monitored

Strategies to promote safety and exercise performance under hot conditions – Fluid intake containing appropriate sodium, carbohydrate, and protein concentrations

– Clothing adjustments

– Modify exercise session

– Heat acclimation

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Appendix 1: Bibliography

American Academy of Pediatrics. Committee on Sports Medicine and Fitness. Climatic heat stress and the exercising child and adolescent. Pediatrics. 2000;106(1 pt 1):158-159.

American College of Sports Medicine. Position stand: exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390.

American College of Sports Medicine. Position stand: exertional heat illness during training and competition. Med Sci Sports Exerc. 2007;39(3):556-572, 2007.

American Dietetic Association, Dietitians of Canada, American College of Sports Medicine. Position stand: nutrition and athletic performance. Med Sci Sports Exerc. 2009;41(3):709-731.

Burke LM, Hawley JA. Fluid balance in team sports. Guidelines for optimal practices. Sports Med. 1997;24(1):38-54.

Casa DJ, Armstrong LE, Hillman SK, et al. National Athletic Trainers’ Association position statement: fluid replacement for athletes. J Athl Train. 2000;35(2):212-224.

Casa DJ, Eichner ER. Exertional heat illness and hydration. In: Starkey C, Johnson G (eds). Athletic Training and Sports Medicine. Boston; Jones and Bartlett; 2005: pp 597-615.

Cheuvront, SN, Carter RC, Sawka MN. Fluid balance and endurance exercise performance. Cur Sports Med Rep. 2003;2(4):202-208.

Costill DL. Sweating: its composition and effects on body fluids. Ann N Y Acad Sci. 1977;301:160-174.

Crandall CG, Gonzalez-Alonso J. Cardiovascular function in the heat-stressed human. Acta Physiol. 2010;199:407-423.

Grandjean AC, Grandjean NR. Dehydration and cognitive performance. J Am Coll Nutr. 2007;26(5 suppl):549S-554S.

Greenleaf JE. Problem: thirst, drinking behavior, and involuntary dehydration. Med Sci Sports Exerc. 1992;24(6): 645-656.

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Appendix 1: Bibliography (continued)

Hew-Butler T, Almond, C, Ayus C, et al. Consensus Statement of the 1st International Exercise-Associated Hyponatremia Consensus Development Conference, Cape Town, South Africa 2005. Clin J Sport Med 2005;15(4):208-213.

Lieberman HR. Hydration and cognition: a critical review and recommendations for future research. J Am Coll Nutr. 2007;26(5 suppl):555S-561S.

Maughan RJ, Leiper JB. Sodium intake and post-exercise rehydration in man. Eur J Appl Physiol Occup Physiol. 1995;71(4):311-319.

Maughan RJ, Shirreffs SM. Dehydration and rehydration in competitive sport. Scand J Med Sci Sports. 2010;20(suppl 3):40-47.

Maughan RJ. Fluid and electrolyte loss and replacement in exercise. J Sports Sci. 1991;9 Spec No:117-142.

Maughan RJ, Shirreffs SM, Leiper JB. Errors in the estimation of hydration status from changes in body mass. J Sports Sci. 2007;25(7):797-804.

Montain, SJ, Cheuvront SN, Sawka MN. Exercise associated hyponatraemia: quantitative analysis to understand the aetiology. Br J Sports Med. 2006;40:98-106.

Murray B. Hydration and physical performance. J Am Coll Nutr. 2007;26(5):542S-548S.

Nadel ER, Wenger CB, Roberts MF, et al. Physiological defenses against hyperthermia of exercise. Ann N Y Acad Sci. 1977;301:98-109.

Passe DH. Physiological and psychological determinants of fluid intake. In: Maughan R, Murray R (eds). Sports Drinks: Basic Science and Practical Aspects. Boca Raton; CRC Press; 2000: pp 45-88.

Sawka MN, Latzka WA, Matott RP, Montain SJ. Hydration effects on temperature regulation. Int J Sports Med. 1998;19(suppl 2):S108-S110.

Wilmore JH, Costill DL, Kenney WL. Physiology of Sport and Exercise, 4th edition. Champaign; Human Kinetics Publishers; 2008: pp 1-574.

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Appendix 2: Unit Conversions

Work or heat: kilojoules (kj) to kilocalories (kcal)

– Multiply kj value by 4.186 to obtain kcal

Temperature: Celsius (C) to Fahrenheit (F)

– Multiply the C value by 1.8 and add 32 to obtain F

Concentrations: millimoles/liter (mmol/L) to milliequivalents/liter (mEq/L)

– Conversion is one-to-one if electrolytes are univalent (single charge)

– Multiply mmol by the charge on the electrolyte if divalent or greater than one

Particles to mass: millimoles (mmol) to milligrams (mg)

– Multiply mmol value by the atomic weight of the element

Metric to English volumes: milliliters (mL) to ounces (oz)

– Divide metric volume by 28 mL to obtain oz

Volume to mass: liters (L) to mass (kg) or ounces (oz) to pounds (lb)

– One-to-one conversion for L to kg (assumes fluid density of 1.00)

– Divide oz value by 16 to get lb

Mass to force: kilograms (kg) to pounds (lb)

– Divide kg by 2.2 to obtain weight in lb

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Appendix 3: Environmental Awareness and Guidelines

A wet bulb, globe, temperature meter (WBGT) or a sling psychrometer can be used to monitor environmental conditions

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Abbreviations: EHS, exertional heat stroke; F, Fahrenheit; C, Celsius. a EHS can still occur due to other factors. American College of Sports Medicine. Med Sci Sports Exerc. 2007;39(3):556-572. Adapted from Casa DJ, Eichner ER. Exertional heat illness and hydration. In: Starkey C, Johnson G (eds). Athletic Training and Sports Medicine. Boston; Jones and Bartlett; 2005: pp 597-615.

WBGT Condition

Fahrenheit Celsius Safety/Risk Action

< 65° 18.3° Generally safea Normal activity

65.1° - 72° 18.4° - 22.2° Risk of EHS for all More or longer rest periods

72.1° - 78° 22.3° - 25.6° Risk for all increased More rest for unfit; normal training for fit/acclimated

78.1° - 82.0° 25.7° - 27.8° Risk for unfit, unacclimated Longer rest intervals, decrease intensity

82.1° - 86° 27.9° - 30° EHS risk Plan intense or long training with caution

86.1° - 90° 30.1° - 32.2° High risks No practice for unfit; limit exercise in fit, acclimated

> 90.1° > 32.3° Uncompensable heat stress Cancel for all athletes

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