Water and Exercise
Water
•
Does not provide any food energy
•
Essential as a medium in which reactions can occur
•
Constitutes the majority of the body’s 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 (can’t 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, you’re
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 don’t appear to inhibit gastric emptying; however less fluid is
usually consumed
–
Citric acid may impair gastric
emptying by 25%
–
Caffeinated drinks don’t 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. Don’t 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