Transcript Sport / Fitness Nutrition

Nutrition for Physical Activity &
Sport
Readings: Chapter 14
Omit “Muscles & Muscle Fibers”, p. 559
What is Physical Fitness?
Definition
• the ability to perform moderate to vigorous
levels of physical activity without undue
fatigue and the capability of maintaining this
level of activity throughout life (ACSM)
Components:
 Cardiorespiratory Fitness
 Muscular Strength
 Muscular Endurance
 Flexibility
Physical Activity vs. Exercise
Physical Activity
– any body movement carried
out by skeletal muscles and
requiring energy
Exercise
– a subset of physical activity
that is planned, structured,
repetitive movement of the
body designed to improve or
maintain physical fitness
Benefits of Regular Physical
Activity
Exercise is one of the most important
things you can do to improve your
wellness!
• sedentary individuals have 50% more health
problems that active individuals including
increased risk of:
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hypertension
diabetes
obesity
hyperlipidemia
osteoporosis
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Benefits of Physical Fitness
improved sleep
nutritional health
healthy body composition
healthy bone mineral density
improved immune function
reduced risk of CVD, Type II diabetes, some
cancers
reduced stress and anxiety
improved self-esteem and lowered risk of
depression
improved cognitive functioning, alertness and
memory
injury reduction and low back pain
greater longevity and quality of life
Becoming more active…
How much is needed to reap health
benefits?
• 60 minutes of moderately intense physical
activity every day*
Is Lifestyle Physical Activity enough?
• increased lifestyle physical activity promotes
improved health and well-being but does not
necessarily improve physical fitness
• exercise programs designed to improve
physical fitness contribute to even greater
improvements in quality of life and greater
reductions in disease and mortality risk
* Recommendations from the
WHO & the Institute of Medicine
Canada’s Guide for Healthy
Active Living
Increase
Endurance
Activities
Increase
Flexibility
Activities
Increase
Strength
Activities
4 - 7 days a week
Continuous activities for your heart,
lungs, and circulatory system.
4 - 7 days a week
Gentle reaching, bending, and
stretching activities to keep your
muscles relaxed and joints mobile
2 - 4 days a week
Activities against resistance to
strengthen muscles and bones and
improve posture
http://www.phac-aspc.gc.ca/pauuap/fitness/pdf/guideEng.pdf
Reduce
sitting for
long
periods
Sources of Energy for
Physical Activity
• physical activity increases the energy
needs of working tissues including the
muscles and the heart…where does this
energy come from?
– ATP & CP
– Carbohydrate: Glucose/Glycogen
– Fat
– Protein
1. ATP & CP
• very small pool of ATP available in cells
• CP (creatine phosphate) can release
phosphate which combines with ADP to
form ATP
• supplies are limited, fuels activity for 3 15 seconds of maximal effort
• anaerobic
exercise
creatine phosphate + ADP
creatine + ATP
rest
ATP-CP Energy System
2. Carbohydrate: Glucose
• derived from muscle & liver glycogen
stores
• fuels activities of extreme intensity (20 s
to 3 minutes):
– oxygen needs of muscle exceed the
ability of cardiovascular system to
supply oxygen
– glucose is used anaerobically
(without oxygen) to produce ATP
– by-product is lactate
Anaerobic Metabolism of
Glucose
2. Carbohydrate: Glucose
• in activities of high intensity (3 to 20
minutes):
– glucose is used AEROBICALLY (with
oxygen) to produce ATP
• in activities of moderate intensity (> 20
minutes):
– glucose oxidation is supplemented
with fatty acid oxidation
3. Fat Metabolism
• initially during exercise blood [fatty acid]
decreases
• after 20 minutes there is an increase in
release of fatty acids from stores
– due to hormone epinephrine (adrenalin)
• endurance training produces adaptations that
enhance the ability to burn fat
– ’d size & number of mitochondria in
muscles
– ’d number of capillaries to supply oxygen
& nutrients to muscles
4. Protein
• not a primary fuel for physical activity
• contributes about 5 - 10% to energy
expenditure both during activity and at rest
Factors that influence protein use during
activity:
– high dietary protein
increase use of
– increased duration of activity
protein as a fuel
decrease use of
protein as a fuel
– increased intensity of activity
– increased training (especially
strength training)
Effect of Intensity & Duration on
Fuel Use
Effect of Intensity & Duration on
Fuel Use
increased duration, decreased intensity
fatty acid oxidation
glucose utilization
decreased duration, increased intensity
fatty acid oxidation
glucose utilization
Summary…
Summary…
Duration
Intensity
Preferred Fuel Source
8 – 10 seconds
EXTREME
ATP - CP
20 sec – 3 min
VERY HIGH
anaerobic glycolysis
3 – 20 minutes
HIGH
aerobic glycolysis
> 20 minutes
MODERATE
fatty acid oxidation
Note: all energy sources are used to some extent at all
times
Effect of Diet on Physical
Endurance
Maximum Endurance Time
• fat and protein diet
57 min
• normal mixed diet
114 min
• high carbohydrate diet
167 min
Diet to Support Physical
Activity
Water
• nutrient required in largest amounts by the
body
• needs increase during physical activity
Body can lose water in four ways:
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–
urine
feces
sweat
respiration
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* Loss increases during physical activity
Water & Temperature
Regulation
• heat production increases 15-20x during exercise
compared to rest
• body cools itself by sweating
– 1 L of sweat dissipates about 600 kcal of heat
– prevents an  in body temperature of about
10°C
• EVAPORATION of sweat cools the body
• blood is rerouted through capillary beds that lie
just beneath surface of skin to cool the blood
• endurance athletes can lose 1.5 L of water or
more during each hour of activity
Lance Armstrong said
blistering temperatures and
not drinking enough fluids
gave him a challenging day
in the saddle during the
2003 Tour de France's
12th-stage time trial, won
by German rival Jan Ullrich.
Water & Temperature
Regulation
• in hot humid weather, need for water ’s
even more
• dehydration not only decreases performance
but can cause dizziness, cardiac arrhythmias,
muscle spasms, delirium, and death
Hydration Schedule
2 hrs before
400 – 600 ml
15 min before
250 – 500 ml
every 15-20 min during
150 - 350 ml
after exercise
500 ml for each lb body weight lost, or 1.5x
body weight lost
Water & Temperature
Regulation
Too much water?
• leads to a condition called HYPONATREMIA
• symptoms include swelling, weight gain,
nausea, and dizziness
• may occur in events where individuals
replace more water than they lose and do not
replace electrolytes causing dilution of
sodium in the blood
Electrolytes
• in addition to contributing to water loss, sweat
also results in loss of electrolytes
– electrically charged minerals
– Na+, K+, Cl-, and Mg2+
• minerals are important for water balance
• losses normally replaced through diet
– for exercises lasting longer than 1 hour,
replacement of fluids with water & electrolytes
may provide a performance advantage
– more important for athletes in competitions lasting
4+ hours with heavy sweating
Replenishing Energy DURING
activity…
• during endurance activities lasting longer
than one hour, glycogen supplies risk
depletion
• maintaining blood glucose levels can prolong
time to exhaustion
• glucose replacement (200 kcal) useful in
activities lasting longer than 1 hour
• sports drinks with 6 - 10% carbohydrates (50
- 100 kcal per cup)
• depends on goal of exercise!
Replenishing Energy AFTER
activity…
• a high carbohydrate meal
eaten within 15 minutes
accelerates rate of
glycogen storage by
300%, called “glycogen
window”
• Are energy bars or drinks
necessary?
Glycogen Depletion and
Fatigue Sensation
Protein in the Athlete’s Diet
• athletes have increased need for protein due
to need to repair and build muscles after
activity (max 2.0 g/kg body weight)
• see Table 13.4 for recommended intakes
• protein intake after exercise helps replenish
glycogen stores
Too much protein? Risks of Supplements:
– dehydration
– displacement of carbohydrates from diet,
insufficient replenishment of glycogen stores
– kidney problems
Fat Intake and the Athlete
• Fat intake should not be overly restricted. There is no
performance benefit in consuming a diet with less
than 15 percent of energy from fat. Extreme fat
restriction limits food choices, especially sources of
protein, iron, zinc, and essential fatty acids.
• Sports nutritionists recommend that any extra fat
calories come from monounsaturated and
polyunsaturated sources.
Vitamins and Minerals
• many vitamins and minerals are important for
energy metabolism
• deficiencies impair performance
• extra from supplements DO NOT enhance
physical performance
Iron
• physically active young women prone to iron
deficiency
• multiple contributing factors
• supplementation should be based on blood
tests, not self-assessment