Water and Exercise
Water
Does not provide any food energy
Essential as a medium in which reactions can occur
Constitutes the majority of the bodys weight (60% in
avg male; 50% in avg female)
Most important for temperature regulation in the body
Water
How much do you need per day?
Approximately 2 to 3 quarts per day;
taken in via fluids (25% of bottled water is actually purified tap water),
food, metabolism
Why?
Water losses during day
Via
v
Urinary output
v
Insensible perspiration
- through skin (~30%)
v
Exhaled air
v
GI tract
Water
Where is it stored in the body?
65% is stored in the inside body
cells (intracellular water)
35% is outside the body cells (extracellular
water)
Intercellular (interstitial) is
between and surrounding cells
Intravascular is within the blood
vessels
Fluid shifts between these
compartments during rest and exercise efforts
Held in the body by protein, CHO, and
electrolytes (sodium in particular)
Water
How is body water regulated?
By the
kidney
Normohydration (Euhydration) normal body water
levels
Dehydration loss of body water
Hyperhydration excess fluid retention by body
Main
feedback device
Osmolality amount of dissolved substances in
solution
Water
Control Mechanism
Major
functions of water in body
Building material for cells
Protection of body tissues (cant compress water)
Control osmotic pressure inside body
Major constituent of blood
Essential for proper functioning of senses
Regulation of body temperature
Electrolytes
Defined as substances in water that conduct an
electric current
Major electrolytes in body
Sodium,
potassium, chloride, bicarbonate, sulfate, magnesium, and calcium
Electrolytes
Sodium
RDA: there
is none at current time; avg minimum for adults is 500 mg/day but suggested to
be 1,250-2,400 mg/day for athletes who sweat profusely
Food Sources
Found in natural and processed foods (more)
Avg American
takes in 4,000-4,800 mg/day
Electrolytes
Sodium
Major
Functions
Control of water balance and pressures; nerve
transmission; muscle contraction
Deficiency
Concentration of sodium increases in blood during
short-term exercise
Prolonged exercise and sweating may decrease sodium
amount, particularly in hot environment leading to heat problems
Electrolytes
Chloride
DRI minimum
is 750 mg/day
Food Sources
Table salt, along with sodium
Major
Functions
Water balance and electric potentials; formation of
hydrochloric acid for digestion of food in stomach
Deficiency
Rare but significant sweating can result in heat
problems
Electrolytes
Potassium
DRI minimum is 2,000 mg/day
Food Sources
Bananas, citrus fruits, fresh
vegetables, milk, meat, fish
Major Functions
Water balance and electric potentials
in nerves and muscles; transport of glucose into muscle, storage of energy in
muscle
Deficiency
Rare but can occur during fasting,
diarrhea, use of diuretics
Symptoms included muscle weakness and
heart stoppage
Excess
Heart ECG dysrhythmias can occur
Fluid
and Electrolyte Losses
How does environmental heat affect physical
performance?
Performance
in strength, power, or speed events that last less than 1 minute is not
adversely affected
Performance
in prolonged aerobic events is worse compared to cooler environments
Fluid
and Electrolyte Losses
How do dehydration and hypohydration affect physical
performance?
Studied from
2 perspectives:
Voluntary dehydration
Individual
choses to lose weight, such as with wrestlers and boxers
Involuntary dehydraton
Water is
lost as a result of training or competition; body attempting to maintain
temperature homeostasis
Note:
Dehydration leads to hypohydration
Fluid
and Electrolyte Losses
Voluntary Dehydration
Usually involves use of
exercise-induced sweating, thermal-induced sweating such as saunas, diuretics
to increase urine losses, and decreased intakes of fluids and foods
4-8% losses in body weight (primarily
water) have resulted in mixed results
Some studies show no effect on
performance in anaerobic events
Anaerobic muscular endurance tasks
lasting longer than 20-30 seconds have shown impaired performances, up to 15%
drops in performance
Impairments possibly due to loss of K+
in muscle and high temperatures in muscle
Fluid
and Electrolyte Losses
Involuntary Dehydration
Usually
associated with prolonged endurance events under warm, humid environmental
conditions
Less than 2%
losses in body weight have shown significant decreases in performance
The greater the losses, the greater the decrement in
performance
Decrements in performance are related to
cardiovascular function and temperature regulation
A 3% weight
loss can decrease aerobic performance by 4-8% in a neutral environment
v
Impairment would be greater in hot environment
Fluid
and Electrolyte Losses
Why are there decrements in performance with
Involuntary Dehydration?
Reduction in
plasma volume
Decreases cardiac output and skin blood flow
Decreases in
skin blood flow lower sweat rate and increase core temperature
HR is
increased and stroke volume is decreased
Increased GI
distress
Symptoms of nausea, vomiting, bloating, cramps
Disturbed
fluid and electrolyte imbalances
Cognitive
function can be impaired with 1-2% dehydration
Fluid
and Electrolyte Losses
How fast does an individual dehydrate while
exercising?
Maximal
sweat rate for a trained athlete is about 2-3 liters/hour; this results in a
2-3% decrease in body weight
Note: 1 liter = 1 kg = 2.2 lbs
So a 2 liter
sweat loss would be equivalent to 4.4 lbs
Football players can lose 5-6 kg (11-13 lbs) over the
course of a day with multiple workouts
Greater sweat losses usually occur with males compared
with females
Fluid
and Electrolyte Losses
What is the composition of sweat?
Depends on the type of sweat gland
Apocrine
Located in hairy areas of body
Secrete an oily mixture to reduce
friction from movement
Eccrine (2-3 million)
Located over surface of body
Primarily involved with temperature
regulation
Sweat is 99% water & hypotonic
(less [ ] of electrolytes compared with body fluids)
Major electrolytes in sweat
Sodium, chloride, along with other
macro and microminerals
Small quantities of N, amino acids
& water-soluble vitamins
Fluid
and Electrolyte Losses
Does excessive sweating result in
electrolyte deficiency?
Levels of Na+ (water loss)
and K+ (leakage from muscle and water loss) increase
Levels of chloride and calcium remain
unchanged
Levels of Mg usually decrease (due to
need from muscle, particularly for prolonged, endurance events)
Prolonged events, without fluid
replacement, have resulted in 5-7% decreases in Na+ and Chloride; K+
decrease of 1%
Overall, no significant loss of
electrolytes provided adequate fluid replacement occurs
Fluid, CHO, and Electrolyte Replacement
Which is most important to replace during exercise in
the heat?
Water
replacement is the primary consideration
CHO drinks
are important for maintaining glucose and glycogen energy sources in prolonged
endurance events
Electrolyte
replacement is important in events with heavy sweat losses (e.g.
ultra-marathons)
Fluid
and Electrolyte Losses
Guidelines for maintaining fluid balance during
exercise
Skin wetting
with cold water
Some suggest this to be detrimental due to decreased
sensation of need to sweat
Athletes
increase effort without the body compensating for heat regulation inside the
body
Others suggest psychological sense of relief
No proven benefit to performance; more research needs
to be done
Fluid
and Electrolyte Losses
Guidelines for maintaining fluid balance during
exercise
Hyperhydration
Increased
hydration prior to an event in hot environment is likely to improve
cardiovascular function and temperature regulation
Recommendation
v
1 pint (16 oz) when waking in morning
v
1 pint at 1 hour before event
v
1 pint at 15-30 min before event
Fluid
and Electrolyte Losses
Guidelines for maintaining fluid balance during
exercise
Rehydration
Shown to
minimize the rise in core temperature, reduce stress on cardiovascular system,
and help maintain optimal race pace (in events of 1 hour or more in the heat)
May reduce
loss of muscle glycogen
Water
ingested during exercise may appear in plasma and sweat within 10-20 minutes
v
This will depend upon gastric emptying and intestinal absorption
Fluid
and Electrolyte Losses
What factors influence gastric emptying?
Total volume
of fluid intake
Caloric
density of drink
Osmolality
of drink
Temperature
of drink
Exercise
intensity
Mode of
exercise
Dehydration
state
Gastric
Emptying
Volume
The larger
the volume ingested (up to 700 ml), the greater the rate of emptying; larger
volumes may cause discomfort
Caloric Density
6-8% glucose
solution is recommended by ACSM; greater than 10% may slow emptying
Gastric
Emptying
Osmolality
Adding
electrolytes and CHO to fluids increase osmolality which slows emptying
Glucose polymer-fructose solutions have shown lessened
effect on gastric emptying
Temperature of solution
Cold fluids
empty from stomach more rapidly than warm fluids
Gastric
Emptying
Exercise
Moderate intensity exercise helps
facilitate emptying while intensities around 70-75% VO2 max have a
slowing effect on emptying
Cycling does not differ from running
during the initial hour of a long exercise; however, gastric emptying is
quicker during later stages of prolonged cycling vs running
Dehydration State
Rate of gastric emptying not affected
by 3% hypohydration, however greater water loss may slow gastric emptying
Intestinal
Absorption
Absorptive capacity of intestines
does not limit the effectiveness of an oral rehydration solution
Water absorption is helped by
presence of glucose and sodium
Glucose stimulates sodium absorption,
and sodium is needed for glucose absorption
Multiple forms of CHO appear to
enhance absorption of water
High intensity exercise may slow
intestinal absorption of water
Individual differences exist in
regard to intestinal absorption
CHO replacement during exercise in heat
Warm environments tend to accelerate
use of muscle glycogen
General findings
GES and GPS solutions between 5-10%
empty stomach as effectively as water
1 gram of CHO per minute of prolonged
activity is recommended
Cola drinks or fruit juices may be
diluted in half (equal parts cola and water)
Higher CHO solutions delay gastric
emptying and cause GI distress (excess gas production, flatulence, sensation of
defecating, and cramping); more so in runners than cyclists
Electrolyte replacement during exercise in heat
Electrolyte replacement is not
necessary during exercise of durations less than 4 hours
Amount of electrolytes in blood
actually increase
Excessive intake may aggravate
electrolyte balance and impair performance
Sodium intake of 20-30 mEq/L (1-2
grams of salt per liter) are recommended for prolonged events such as
ultramarathons and triathlons
Water intake alone, without some Na+
may lead to hyponatremia (subnormal amount of Na+ in blood)
Chicken broth or chicken noodle soup
has been shown to help with fluid retention after dehydration
Electrolyte replacement during exercise in heat
Hydration Check
Check body
weight in morning; if you weigh several pounds less from previous day, youre
most likely hypohydrated
Are salt tablets or K+ supplements necessary for
exercise in hot conditions?
General Information
Salt is 40%
Na+ and 60% Cl
Less salt
will be lost in an acclimatized compared to an unacclimatized individual
Average meal
contains 2-3 grams of Na+
Total for 3 meals is usually enough to cover Na+
lost in sweat
Are salt tablets or K+ supplements necessary for
exercise in hot conditions?
Recommendations for Salt Intake
In general,
salt tablets not needed with regular well-balanced meals
10-25 grams
of salt (4-10 g Na+) per day is recommended for athletes
acclimatizing to heat over 1-2 week period; 2-3 grams for sedentary individuals
acclimatizing to heat
Are salt tablets or K+ supplements necessary for
exercise in hot conditions?
Recommendations for Salt Intake
Salt tablets
should only be taken if athlete needs to drink more than 4 quarts of water/day
to replace weight loss (8 lbs); i.e. 1 pint of water per salt tablet; (1 pint=1
lb)
After 6-9
days of acclimatizing, use of salt tablets should be discontinued
Are salt tablets or K+ supplements necessary for
exercise in hot conditions?
Recommendations for K+ supplements
Not
recommended
A large
glass of orange juice will replace K+ lost in 2 liters of sweat
Prudent Recommendations of Fluid Replacement with Exercise in
Hot Conditions
Before Competition
Be well-trained and acclimatized
Be well-hydrated the day before and
morning of competition
Hyperhydrate (10-17 oz or 300-500 ml)
of cold fluid at 15-30 minutes before exercising
If exercise is prolonged, add CHO to
fluid (6-8% glucose solution)
Minimize consumption of alcoholic
beverages the night before competition; could lead to hypohydration
Avoid drinking caffeinated beverages
1-4 hours prior to competition; may increase urine production during rest
Prudent Recommendations of Fluid Replacement with Exercise in
Hot Conditions
During Competition
Drink cold water (40-50oF or 4.4-10oC)
when CHO intake is of no concern, i.e. events less than 50-60 minutes
For events longer than 60 minutes, CHO drinks (6-8%)
should be considered; multiple forms (glucose, sucrose, fructose, glucose
polymers) of CHO drinks may be helpful
Prudent Recommendations of Fluid Replacement with Exercise in
Hot Conditions
During Competition
3. Drinks should
contain small amounts of electrolytes, particularly for events of prolonged
duration (4-5 hrs)
460-690 mg Na+/liter
200-400 mg K+/liter
4. Fluid should be
palatable
Cold and sweet enhances palatability
Carbonated beverages nor use of
aspartame dont appear to inhibit gastric emptying; however less fluid is
usually consumed
Citric acid may impair gastric
emptying by 25%
Caffeinated drinks dont appear to
have detrimental effect when consumed during exercise
Prudent Recommendations of Fluid Replacement with Exercise in
Hot Conditions
During Competition
5. Rehydrate with 6-8
oz (180-240 ml) of cold fluid during exercise at 10-15 minute intervals
One normal mouthful/swallow = 1 ounce
Per minute, 50 ml of fluid may be
lost through sweating (up to 3 liters per hour) but only 20-30 ml of fluid may
be absorbed from intestines in that time
4. Rehydrate early in
endurance events
Thirst does not develop until ~ 1-2%
of body wt has been dehydrated
Note: dehydration may
impair gastric emptying and cause GI distress
Prudent Recommendations of Fluid Replacement with Exercise in
Hot Conditions
After Competition
1. Consume enough
fluids to regain body weight losses
Consume 150% of body wt loss; or 24
ounces of fluid for each 16 oz lost
Consume fluids with high CHO content;
fruit juices and sport drinks are good choices
Combining CHO with protein in drinks
may speed rate of glycogen replacement
2. Consume drinks with
some Na+ or you can add some salt on your foods
3. Avoid caffeinated
beverages
a. These can increase electrolyte losses during recovery
4. Avoid alcoholic
beverages containing 4% or more alcohol
a. These delay restoration of blood volume
Prudent Recommendations of Fluid Replacement with Exercise in
Hot Conditions
In Training
1. Practice consuming fluids while you
train
Consuming GES during training may result in more
effective workout
Try different fluid combinations at various training
intensities to determine what works best for you
Ergogenic
Effects of Water
Compared to taking no fluid before or
during competition, hyperhydration and rehydration can enhance temperature
regulation and exercise performance
Long duration performances are
affected the most when not getting proper hydration
Diuretic-induced water losses have
been shown to be effective for high jumpers
Can develop same power output but
with less body weight
Use of diuretics is banned by USOC and
NCAA
Extra Na+ ingestion may
theoretically increase blood volume leading to better cardiovascular responses
but no advantages have been reported
Does glycerol supplementation enhance endurance performance
in hot weather?
Glycerol + water hyperhydration
Suggested to increase osmotic
pressure of body fluids which may increase blood volume
This could enhance temperature
regulation, hence improve performance
For each kg of body wt, 1 g of
glycerol is combined with water
Some studies have shown twice as much
water is retained with glycerol-induced hyperhydration; others show no
advantages
Studies have shown improvements in
endurance cycling performance; others show no benefit runners have to use
more energy to move water around
Suggested improvement in giving body
builders cut appearance
Does glycerol supplementation enhance endurance performance
in hot weather?
Glycerol + water hyperhydration
Should be
cautious in excess use of glycerol since it may increase pressures in
intracellular spaces causing tissue damage; also may cause nausea, vomiting,
headaches
Glycerate is
the commercial product
Pro Hydrator contains glycerol
Glycerine is sold in stores
This must be
diluted, not taken internally in store form
v
Dilution is 36 ml of glycerol with 955 ml of water for
each 100 lbs of body wt (1.25 oz per quart of water)
Does sodium bicarbonate (soda loading) improve performance?
Sodium bicarbonate (baking soda) is an alkaline salt
found naturally in the body which controls excessive acidity
During high
intensity anaerobic exercise, it can buffer large amount of lactic acid
accumulation in the blood
It can have
potential benefits on each of the energy systems
Does sodium bicarbonate (soda loading) improve performance?
Sodium bicarbonate and the energy systems
ATP-PC
system
No ergogenic effect on intense efforts < 30 seconds
or resistance exercise tasks
Does sodium bicarbonate (soda loading) improve performance?
Sodium bicarbonate and the energy
systems
Lactic acid system
Ingestion of sodium bicarbonate or
sodium citrate has generally shown:
Decreased acidosis in the muscle
Decrease sense of fatigue during
exercise
Increase in exercise performance in
events of 1-3 minutes of high intensity
Other studies suggest no improvement
in performance but not hindrance either
If taken, recommendation
Take 0.15-0.30 g sodium bicarbonate
per kg body wt (< 1 oz for avg adult)
Take dosage 1-3 hours prior to
exercise task
Does sodium bicarbonate (soda loading) improve performance?
Sodium bicarbonate and the energy systems
Oxygen
system
Some studies suggest a beneficial effect on
performance in events of 4-5 minutes duration and possibly up to 60 minutes of
exercise effort
Other studies have shown no benefit in maximal runs of
4-30 minutes duration
Sodium
Bicarbonate Use
Safety
Generally
safe, but excessive dosages may cause GI distress or alkalosis with symptoms of
apathy, irritability, and muscle spasms
Legality
Still legal
to use soda loading
No test to detect its use, except for urinary pH
Difficult to
quantify since this may be affected by antacids
Water
and Health Aspects
Heat Injuries
Heat Syncope
Heat Cramps
Salt-depletion
heat exhaustion
Water-depletion
heat exhaustion
Anhidrotic
heat exhaustion
Heat Stroke
Heat
Syncope
Heat
Cramps
Salt-depletion
Heat Exhaustion
Water-depletion Heat Exhaustion
Anhidrotic
Heat Exhaustion
Heat
Stroke
How do you reduce problems with exercising in heat?
Check temp and humidity before
exercise
Exercise in morning or evening
Exercise in the shade; wear sunscreen
Wear thin clothing that is loose to
allow air circulation; loose hat in the sun
Run into breeze in latter portion of
your run
Drink cool fluids periodically (6-8
oz every 10-15 min)
Replenish water daily (drink 16-24
oz/pound lost)
Hyperhydrate if performing prolonged
strenuous exercise (16-32 oz at 30-60 min prior to start of exercise)
How do you reduce problems with exercising in heat?
9. Replenish lost electrolytes (salt) if
sweating excessively
10. Avoid excessive intake of protein; protein
metabolism increases heat production by body
11. Avoid consuming caffeinated beverages several
hours before exercise; it is a diuretic and increases metabolism
12. Avoid alcohol the evening before exercise
13. If out-of-shape, exercise at low intensities
14. Be aware of signs and symptoms of heat
illnesses
15. Dont exercise when ill or had fever recently
16. Become acclimatized to heat before exercising
in warm-hot competitive conditions
How do you become acclimatized?
Living in a warm environment will
confer some adjustment to heat
Physical training will provide ~50%
acclimation and increase body water levels
Techniques for acclimatization (takes
7-14 days; longer for children)
Cut down the amount and intensity of
exercise in beginning stages of acclimation
Increase amount and intensity of
exercise as adjustment to heat occurs
Mimic warm/hot environment in
temperate areas
Exercise in warm environments
Wear extra layers of clothes
Physiological responses to acclimatization
Plasma volume expands resulting in
greater total blood volume; blood vessels conserving more protein and Na+
Extra blood volume allows for greater
stroke volume
More blood volume allows more O2
and nutrient delivery to muscles; more blood to skin to allow for more
efficient cooling
Less muscle glycogen is used, sparing
important energy for performance
Sweat glands hypertrophy and secrete
30% more sweat; greater evaporation
Physiological responses to acclimatization
6. The amount of salt in sweat decreases by ~
60%; evaporation is more efficient and electrolytes are conserved
7. Sweating starts sooner at a lower core
temperature
8. Core temperature will not rise as high or as
rapidly as when it did in unacclimatized state
9. Psychological feeling of stress is reduced
during exercise