Athletes need both!

1

Heat Removal• Exercise increases core temperature.

For every L of O2 consumed during exercise ~5 kcal is produced but

only 1kcal is used for mechanical work –

the rest is heat

• Increases in core temperature:

– Increase blood flow to the skin– Initiate sweating

Sweating and Fluid Loss• Mild to moderate work and

routine physical training typically result in whole-body sweat losses of about ~0.8-1.4 L/h.

• Evaporation of 1L of water from the skin will remove 573 kcal of heat from the body.

• Heat loss via evaporation of sweat is largely dependent on the humidity (proximate to the skin) in which the athlete is working.

• Individual sweat rates and fluid losses vary widely between athletes and across sports.

Avoid “Hitting the Wall”Avoid “Hitting the Wall”

Body weight loss (%)

Exe

rcis

e C

apac

ity

0 21 3 4 5

60%

80%

100%

In cool laboratory conditions, VO2max has been shown to decrease with fluid losses > 2% BW...

In the heat, sweat rates increase even more such that fluid intake must be even more closely monitored.

Effects of dehydration on sports performance.

% OF BODY WEIGHT LOST AS SWEAT

PHYSIOLOGICAL EFFECT

4% CAPACITY FOR MUSCULAR DECREASES

5% HEAT EXHAUSTION

7% HALLUCINATIONS

10% CIRCULATORY COLLAPSE / HEAT STROKES

How does sweating (fluid loss) work to decrease performance?increase in plasma osmolarity (higher

concentration of solute in solution)

release of vasopressin (ADH) from the posterior pituitary gland.

ADH causes the kidney to re-absorb water

Urine volume goes DOWN dramatically to preserve blood osmolarity, volume and pressureAs exercise progresses, the transfer of body water into the plasma cannot keep up with sweat losses so...performance decreases.

Daily Water BalanceAthletes need to be fully hydrated before

training/competition

The average sedentary person excretes about 2700 milliliters of water/day (1400 from urine, 1100 sweat/breath)

To replace that 2700 ml, get:

• 300-400 ml from metabolism, • 1000 ml from food and • 1300-1400 ml from beverages

2700 ml

Athletes and Daily Water Athletes and Daily Water BalanceBalance

Water Balance: Normal

0

500

1000

1500

2000

2500

Output Intake

MetabFoodFluidsStoolBreathSweatUrine

Water Output:Normal vs.Exercise

0

1000

2000

3000

4000

5000

Normal Exercise

StoolBreathSweatUrine

Water Intake: Normal vs Exercise

0

1000

2000

3000

4000

5000

Normal Exercise

MetabFoodFluids

In comparison to non-athletes:

• Athletes greatly increase their water loss– Large increases in sweat loss– Some decreases in urine loss

• Athletes need to greatly increase water intake– Large increases in fluid consumption– Smaller increases in food water and metabolic

water– Athletes often fail to consume adequate amounts

of fluids to maintain optimal hydration status

Guidelines

1. Intake approximately 500ml. (2 cups) of a cool beverage 2 hours before a workout, 250ml (1 cup) in final 15-30 minutes.

2. During activity, drink fluid frequently- for example, 150 -200ml(1 cup) every 15-20 minutes.

3. After a workout, replenish fluids at a rate of 1litre for every kilogram of body weight lost. Weight should be regained, before the next workout, indicating rehydration.

• Pre Activity

• Hydrate properly before prolonged exercise in hot environments.

•Water is the ideal fluid replacement, although flavored beverages may be more effective at promoting drinking.

• The salt in the beverages or as food can promote rehydration more effectively than plain water when significant weight loss has occurred through sweating.

• Urine should be pale yellow or clear. This indicates that you are in a hydrated status

Sports Drinks

TYPE CONTENT

ISOTONIC FLUID, ELECTROLYTES , 6-8% CARBOHYDRATE

HYPOTONIC FLUID , ELECTROLYTES , LOW CARBOHYDRATE

HYPERTONIC HIGH LEVEL OF CARBOHYDRATE

The osmolality of a fluid is a measure of the number of particles in a solution.

In a drink, these particles will comprise of carbohydrate, electrolytes, sweeteners and preservatives.

In blood plasma the particles will comprise of sodium, proteins and glucose.

Blood has an osmolality of 280 to 330mOsm/kg. Drinks with an osmolality of 270 to 330mOsm/kg are said to be in balance with the body's fluid and are called Isotonic.

Hypotonic fluids have fewer particles than blood and Hypertonic have more particles than blood.

Consuming fluids with a low osmolality, e.g. water, results in a fall in the blood plasma osmolality and reduces the drive to drink well before sufficient fluid has been consumed to replace losses.

Isotonic - quickly replaces fluids lost by sweating and supplies a boost of carbohydrate. This drink is the choice for most athletes - middle and long distance running or team sports. Glucose is the body's preferred source of energy therefore it may be appropriate to consume Isotonic drinks where the carbohydrate source is glucose in a concentration of 6% to 8% - e.g. High Five, SiS Go, Boots Isotonic, Lucozade Sport.

Hypotonic - quickly replaces fluids lost by sweating. Suitable for athletes who need fluid without the boost of carbohydrate e.g. jockeys and gymnasts.

Hypertonic - used to supplement daily carbohydrate intake normally after exercise to top up muscle glycogen stores. In ultra distance events, high levels of energy are required and Hypertonic drinks can be taken during exercise to meet the energy demands. If used during exercise Hypertonic drinks need to be used in conjunction with Isotonic drinks to replace fluids.

SALT

INSIDE CELL OUTSIDE CELL

DEHYDRATION

WATER

ELECTROLYTES

Electrolytes are electrically charged particles that conduct electricity as they dissolve in

liquids such as water or blood.

SODIUM “ THE YOUTH ELEMENT”

• Keeps joints limber

• 60% is present in the fluid outside the cell;10% is present inside the cell;30% is present in the bones.

• Excessive sweat causes sodium loss as in

Hard manual labor Professional athletes Starvation Vomiting & diarrhoea

POTASSIUM “THE ALKALISER”

• Makes up 5% of the mineral content of the body.

• Plays a vital role in making muscle protein from amino acids.

• Concentration of sodium and potassium are inversely proportional to each other.

• Dehydration depletes potassium and increase muscle breakdown

FUNCTIONS OF ELECTROLYTES

• Regulates water balance

• Interacts with the cell membranes to allow nutrients to enter cells and waste to leave

• Maintains acid-base balance

• Conducts nerve impulse

40% INTRA

CELLULAR

60% OF BODY WEIGHT

20% EXTRA

CELLULAR

BODY WATER

WATER BALANCE

Body water

Food stuffs700 ml Metabolic

water 300ml

Drinking H2O& beverages

1500 ml

Urine1500 ml

Skin450 ml

Lungs400 ml

Feces150 ml

INTERESTING FACTS ON WATER

• Water delivery inside the cells is more effective in the nights when the body is horizontal

• When we drink enough water to pass clear urine, we also pass out a lot of the salt that was held back

• Nothing kills life quicker than lack of water

• The salinity of the water outside the cells in our bodies is the same as the ocean

Heat and Sweat Production During Exercise

• Evaporate 1 liter sweat = 580 Cal heat

• 720 Cal heat = evaporates 1.24 liters of sweat

• Real conditions, approx. 2 liters

Strategies for Avoiding Dehydration

• Establish a hydration protocol for athletes

• Determine individual sweat rate– Changes in body weight (pre-

post weighings)– 1 kg = 1043ml

additional fluids during exercise

– May also account for urine volume

– Goal: no weight loss (or < 2% wt loss)

– Urine color or urine specific gravity

Strategies for Avoiding Dehydration

Emphasize continual fluid replacement• Replace fluids as they are lost• Practice fluid replacement

– Gradually increase fluids– Body adapts to increase fluid consumption– Generally, cold fluids more rapidly absorbed

• Use individual clear bottles for visual monitoring

• Old Rule of Thumb:– 0.5-1 cup per 10-15 min– Individualize is far better

Strategies for Avoiding Dehydration

• Understand each athlete’s sport dynamics– Rest breaks/time outs– Fluid accessibility

• Establish athlete’s acclimatized state– Non-Acclimatized athletes

• sweat more• lose more electrolytes

Strategies for Avoiding Dehydration

• Anticipate high risk conditions• High temperature

– Uniform/clothing effects

• High humidity– Indoor sports– Uniform/clothing effects

• Low air movement– Uniform/clothing effects

• Bright sun– Dark colored clothing

Strategies for Avoiding Dehydration

• Hyperhydration– 500 ml, 15-30 minutes prior to exercise– Limited benefits

• Post-exercise rehydration– Ideally completed within 2 hrs

• ACSM/ADA rec: 700ml per 500gms body weight lost

• Replace CHO and electrolytes at same time to speed rehydration

Example:• Joe played tennis for two hours( 120 mins). He drank a

500ml bottle of water during his workout.– Initial weight = 70– Post-exercise weight = 68

• Water loss =70-68 = 2 kgs• % body weight loss = 2/70 = 2.8% (dehydrated)• Total sweat loss = approx 2 litres• To stay hydrated within 2% (minimum fluid

replacement rate)– 2% x 70 = 1.4 kgs allowed wt loss = 1.4 litres allowable sweat

loss• Maximum fluid replacement rate

– 1.4 lits/ 120 min = 11ml/min = 175 ml every 15 min• Recommended fluid replacement (per 15 min)

– 2.5-10 oz every 15 min

Sport DrinksWater, CHO, electrolytes replacement during

exercise

• Provide water• Provide dilute carbohydrates

– should be < 10% (<8% optimal)– Gatorade: G+S @ 6%– Powerade: F+GP @ 8%– Fruit juice: F+S @ 11-15%– Soft drinks: F @ 11%

Carbohydrates in Sport Drinks

• Glucose– rapidly absorbed and utilized by muscle

• Fructose– more slowly absorbed and utilized by liver

to replace liver glycogen• Sucrose (G-F)• Glucose Polymers

– lower osmolarity than simple sugars and may allow for more rapid water absorption

Sport Drinks•Provide electrolytes during

exercise– replace Na and Cl lost in sweat– enhances water uptake

• [NaCl] < 1000mg/L – Gatorade: Na,Cl,K,P (460mg/L)– Powerade: (Na,Cl) (300mg/L)– Orange Juice: (10 mg Na/L)– Soft drinks: (40 mg Na/L)

Homemade Sport Drink

• lemonade mix(nimbu pani powder)• 1000ml water• ¼ - ½ tsp salt• 6 tablespoon Glucose• 1 tablespoon Sucrose• ½ tbsp baking powder