Sports nutrition
Pennington Biomedical Research Center
Nutrition for Health Professionals
Benefits of exercise
People who are physically active on a regular
basis have a reduced risk of hypertension, heart
disease, diabetes, osteoporosis, depression,
anxiety, sleep problems, and frailty.
Exercise reduces the risk of gaining weight and
becoming obese, reduces the risk for stroke and,
now we have some very good data that indicates
that certain types of cancer may be reduced by
exercise.
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Exercise has Specific
Benefits on:
Cardiovascular health
– Increases heart strength and overall cardiovascular
function, which decreases chance of developing
coronary heart disease and stroke
– Helps maintain healthy blood pressure
– Can increase HDL-cholesterol and lower
LDL-cholesterol and triglycerides in the blood
Obesity
– Helps maintain lean tissue and promote loss of fat
tissue
– Assists in better control of appetite & increases
energy expenditure
– Helps prevent or reverse development of diseases
associated with obesity including type 2 DM, HTN, and
CVD (even if one can’t attain a more healthy weight)
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Exercise has Specific
Benefits on:
Muscular health
– Contributes to building and maintaining muscle
mass and muscle tone
Diabetes
– Increases glucose uptake by muscle tissue cells
independent of insulin action
– Contributes to energy balance, which decreases
risk of type 2 diabetes and related
complications
Osteoporosis
– Helps strengthen bones and contributes
to joint health
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Exercise has Specific
Benefits on:
Infections
– Reduces susceptibility to respiratory and other
infections by enhancing various functions of
the immune system
Cancer
– Reduces risk of colon cancer, and likely breast
cancer
Gastrointestinal health
– Improves peristaltic function and colonic
mass movements
– Lessens risk for gallstones and related
gallbladder disease
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Exercise has Specific
Benefits on:
Fewer Injuries (from falls)
– Contributes to balance and agility, especially in
older adulthood
Psychological health
– Reduces depression, anxiety, and mental
stress, while enhancing a sense of well-being
and self- image, and improving sleep patterns
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Recommendations:
Experts
recommend that,
to help yourself
stay with an
exercise program,
you should:
– Start slowly
– Vary your workouts; make it fun
– Workout with friends and others
– Set specific attainable goals and monitor
progress
– Set aside a specific time each day for exercise;
build it into your routine, but make it convenient
– Reward yourself for being successful in keeping
up with your goals
– Don’t worry about occasional setbacks; focus on
the long-term benefits to your health
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Diet
There is nothing unique about the optimal diet for
a person who is in an exercise program. One
important aspect about physical activity and its
interaction with nutrition is that, when people
become physically active, research shows that
they will spontaneously eat more.
Over time, exercised individuals will be able to
maintain their energy balance, reducing weight
gains that occur with aging.
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Energy Needs
Because of the increased energy demands of
physical activity, individuals need to eat
a little bit more in their diet to maintain their
body weight.
This, in turn, means that they are spontaneously
getting more of the other types of nutrients in
their diet: protein, vitamins, and minerals.
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Supplements
An exercise program combined with
supplemental protein or micronutrients has no
great benefits over exercise alone as far as
increasing aerobic capacity, muscle strength,
and function.
To date, there is little added benefit from
the nutritional manipulation on performance.
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Protein:
Supplementation
There is no evidence whatsoever that
increasing protein over and above what people
normally take in their diet will optimize the
gain in muscle mass with exercise or optimize
performance. Most Americans well exceed
the RDA for protein each day anyways.
So, for healthy men and women, adding
protein supplements is not going to help at all.
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Protein:
Athletes
Typical protein needs for athletes range from
1.2 to 1.6 g/kg body weight.
For endurance athletes, about 10% of energy
comes from protein and these individuals should
aim for the higher value.
Untrained subjects undergoing endurance
training increase their protein need to about
1.0 to 1.2 g/kg/d, well above the RDA of 0.8
g/kg body weight.
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Protein:
Body building
In the initial stages of body building when a lot
of new tissue is being built, intake should be
around 1.8-2.0 g/kg body weight.
This is probably due to the fact that
resistance exercise seems to exert an anabolic
effect and allows for better protein utilization.
Once the desired muscle mass is achieved,
protein intake need not exceed twice that of
the RDA (
>
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1.6 g/kg).
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Protein:
Older Adults
A subset of about 20 to 25% of older men
and women may not get the RDA for protein.
For them (and the very frail, or with denture
problems and poor food intake) increased
protein intake is recommended when they are
starting an exercise program.
Protein should be from food sources, not
from supplements. Milk shakes and other
dairy-based foods can greatly help.
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Protein:
Toxicity
There could be a toxicity risk when people start
consuming too much protein (over 2.0 g/kg/d).
An excessive load of protein represents a
stressful stimulus for the kidney. This is even
more of a concern as we get older, when the
kidneys activities decrease.
Very high protein diets will result in overworking
the filtration system of the kidneys.
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AA:
Supplements
Amino acid supplements are widely used by
athletes. These supplements are not digested
and absorbed in the body as readily as amino
acids coming from food sources.
Moreover, amino acid supplements tend to cause
an imbalance of the amino acids already present
in the body.
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Fuels for muscle cells
Source/System
ATP
When in Use
Examples of an
Exercise
At all times
All types
All exercises initially; extreme exercise
thereafter
Shotput, jumping
Carbohydrate
(anaerobic)
High-intensity exercise, especially lasting
30 seconds to 2 minutes
200-yard (20 meter)
sprint
Carbohydrate
(aerobic)
Exercise lasting 2 minutes to 4-5 hours; the
higher the intensity, the greater the use
Basketball, swimming,
jogging
Fat
(aerobic)
Exercise lasting more than a few minutes;
greater amounts are used at lower exercise
intensities
Long-distance running,
long-distance cycling;
much of the fuel used in a
brisk walk is fat
Protein
(aerobic)
Low quantity during all exercise; moderate
quantity in endurance exercise, especially
when carbohydrate fuel is lacking
Long-distance running
Phosphocreatine
(PCr)
Phosphocreatine
(PCr)
During periods of relaxation, muscles synthesize PCr from ATP and
creatine and then store this in small amounts. As soon as ADP, from the
breakdown of ATP, begins to accumulate in a contracting muscle, an
enzyme is activated that transfers a high-energy Pi from PCr to ADP,
thus reforming ATP.
PCr + ADP  Cr + ATP
Advantage of PCr: It can be activated instantly and
can replenish ATP at rates fast enough to meet the
energy demands of the fastest and most powerful
sports events.
Disadvantage of PCr: Not enough is made and
stored in the muscle to sustain a high rate of ATP
resupply for more than a few minutes.
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Anaerobic Pathway
Carbohydrate
The anaerobic pathway has three major
disadvantages:
– It can’t sustain ATP production for long
– Only about 5% of the energy available from
glucose is released during glycolysis
– The rapid accumulation of lactate greatly
increases the acidity of muscle cells
Because high acidity inhibits the activity of key
enzymes in glycolysis, anaerobic ATP production soon
slows and fatigue sets in.
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Aerobic Pathway
Carbohydrate
If there is plenty of oxygen available in muscles
(aerobic state) and the physical activity is of
moderate to low intensity (jogging or distance
swimming), then the bulk of pyruvate produced by
glycolysis is shuttled to the mitochondria and
further metabolized into carbon dioxide and water
in a series of reactions.
Although the aerobic pathway supplies ATP more
slowly than does the anaerobic pathway, it releases
more energy.
In addition, ATP production via the aerobic pathway
can be sustained for hours.
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Fat
Main fuel for prolonged low-intensity exercise
Factors that increase the rate at which muscles
use fatty acids for energy.
– How much the particular muscle is trained
Muscles that are highly trained contain more,
larger mitochondria when compared to similar
untrained muscles.
– The concentration of fatty acids released from
adipose stores into the bloodstream
If more is present, then more will be used.
– Length of exercise
As exercise becomes increasingly prolonged, fat
use predominates (especially if exercise remains at
a low->moderate aerobic rate).
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Protein
Minor fuel source, primarily for endurance exercise
Although amino acids derived from protein are
used to fuel muscles, their contribution is
relatively small when compared with that of
carbohydrate and fat.
Only about 5% of the body’s general energy
needs are supplied by proteins.
However, proteins can contribute significantly
to energy needs in endurance exercise,
perhaps as much as 10-15%, especially as
glycogen stores in the muscle are exhausted.
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Fuel Use and Sources
A 100-meter sprint is powered by stored ATP,
creatine phosphate, and glycolysis of muscle
glycogen producing lactic acid.
A 1000-meter run is powered at first by ATP,
creatine phosphate and glycolysis and also
some fat oxidation.
Marathon: ATP generated equally from
glycogen and fatty acids are used as fuel for
marathons.
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Velocity versus Fuel
ATP
More Carbohydrate
More Fat
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Energy Needs
The daily energy needs of an athlete depend on
his/her activity factor. A high level of sustained
activity can double the daily energy required for
BMR and activity.
Weight maintenance indicates adequate caloric
intake.
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Energy Needs
Calories are an important factor but not one to
worry very much over because normal appetite
regulation will enable individuals to adjust their
intake, depending on what their energy expenditure
dictates.
If a person starts an exercise program, his/her
appetite will generally increase to meet the body's
extra needs and, in this way, the individual will be
able to maintain weight.
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Vitamins and Minerals
Higher energy intake generally assures greater
intake of vitamins and minerals if sensible
meals are consumed.
Long distance and marathon runners may
require iron supplementation due to breakdown
of red blood cells during prolonged running
events.
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Carbohydrate Loading
Days
1
2
3
4
5
6
Exercise Time
(minutes)
Rest
20
20
40
40
60
Carbohydrate
(g)
600
450
450
450
600 600
“Appropriate” Activities for
Carbohydrate Loading…
Marathons
Long-distance swimming
Cross-country skiing
30-k runs
Triathlons
Soccer
Long-distance canoe racing
Cycling events
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“Inappropriate” Activities
for Carbohydrate Loading…
Football games
10-k runs
Walking and hiking
Most swimming events
Basketball games
Weight lifting
Most track and field
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Fluids
One nutrient that we don't often think about that
is essential for a successful exercise program—
fluids! It is important to monitor the hydration
level of the physically active person.
Many people are dehydrated subclinically,
especially older individuals or people who are
exercising in heat and, in these situations,
hydration needs go up precipitously.
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Fluids
Active people should be encouraged
to drink more non-alcoholic, noncaffeinated fluids when they become
physically active.
At least eight (8 ounce) glasses of
fluids per day.
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Dehydration
Athletes that depend on weight class to enter an
event run a risk of dehydration.
As little as 3% loss of body weight as water
impairs performance, particularly endurance
events.
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Normal weight
0
2
4
6
8
Thirst
Stronger thirst, vague discomfort
Economy of movement, impatience, sleepiness,
apathy
Tingling in arms, feet, headache, increase in
body temperature
Dizziness, cyanosis, indistinct speech, mental
confusion
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Normal weight
10
15
Spastic muscles, general incapacity,
delirium, failing renal function
Shriveled skin, inability to swallow,
sunken eyes, painful urination
Cessation of urine formation, cracked
skin, bare survival limit
20
Death
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Exercising in Hot
Climates
Heat related illnesses include
–
heat cramps, heat exhaustion, and heat stroke.
Heat cramps are deemed the most benign. They
are characterized by painful spasms of the
skeletal musculature, particularly the legs. The
body temperature is usually normal.
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Exercising in Hot
Climates
Heat exhaustion is characterized by fluid
depletion. Patients tend to present sweating
profusely. Symptoms include headaches, nausea,
vomiting, dizziness, and syncope. Treatment
includes rest, rehydration (which often needs
to be given intravenously), and cooling.
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Exercising in Hot
Climates
Heat stroke is a life threatening emergency defined
as a high core temperature (>40C°) accompanied by
neurological symptoms. The presentation can range
between a patient with minimal to no sweating, to a
patient with profuse sweating.
The patient should be moved to a cool environment,
clothing removed and evaporative cooling of the skin
encouraged by spraying tepid water over the body,
while electric fans are directed at the patient. If
available, bags of ice should be placed over the
major vessels in the axillae, groin and neck or ice
water baths.
Heat stroke requires treatment in the ER.
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People who would not benefit
from an exercise program
Those with unstable medical conditions:
• Unstable angina
• Out-of-control diabetes
• Uncontrolled blood pressure
• Or patients who have experienced
other serious medical events
within the last six months
– These listed individuals should not have a regular
exercise program until their condition has better
stabilized. Also not beneficial for those
immediately after a major surgery, those with a
progressive neurological disorder, or any type of
progressive disease state that has not been
stabilized.
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References
Wardlaw G., Kessel M. Perspectives in nutrition.
5th ed. 2002.
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Pennington Biomedical
Research Center
Division of Education
Phillip Brantley, PhD, Director
Pennington Biomedical Research
Center
Claude Bouchard, PhD, Executive
Director
Heli J. Roy, PhD, RD
Shanna Lundy, BS
Beth Kalicki
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About Our Company
The Pennington Biomedical Research Center is a world-renowned nutrition research center.
Mission:
To promote healthier lives through research and education in nutrition and preventive medicine.
The Pennington Center has several research areas, including:
Clinical Obesity Research
Experimental Obesity
Functional Foods
Health and Performance Enhancement
Nutrition and Chronic Diseases
Nutrition and the Brain
Dementia, Alzheimer’s and healthy aging
Diet, exercise, weight loss and weight loss maintenance
The research fostered in these areas can have a profound impact on healthy living and on the prevention of
common chronic diseases, such as heart disease, cancer, diabetes, hypertension and osteoporosis.
The Division of Education provides education and information to the scientific community and the public
about research findings, training programs and research areas, and coordinates educational events for the
public on various health issues.
We invite people of all ages and backgrounds to participate in the exciting research studies being conducted
at the Pennington Center in Baton Rouge, Louisiana. If you would like to take part, visit the clinical trials
web page at www.pbrc.edu or call (225) 763-3000.
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