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Energy Systems of the Endurance Athlete
APRIL ‘05 Athletics Canada Camp:
hosted by Guelph National
Endurance Centre (NEC)
Dr. Trent Stellingwerff, PhD
-University of Guelph-
Good Websites and References:
Health and Science Journal Search Engine:
www.pubmed.com
Gatorade Sports Science Institute:
www.gssiweb.com
American College of Sports Medicine:
www.acsm.org/index.asp
Energy Systems of the Endurance Athlete
PRESENTATION OVERVIEW
1. Basic body physiology
2. Three ways to provide energy
3. Intensity drives fuel selection
4. Improving physiological components of
running performance
Energy Systems of the Endurance Athlete
- 1. Overview of Basic Body Physiology A. ATP = ENERGY
B. Bodies ability to store fuel (CHO vs. FAT)
(pro’s and con’s of each fuel)
C. Fast vs. slow twitch muscle
ATP = ENERGY
- ATP stands for Adenosine Triphosphate
- Basic Molecule that provides the body with energy:
- Basal Metabolic Rate (BMR)- minimum amount of energy
to keep a person alive.
- Provide energy to breakdown food for the body
- ENERGY for ANY type of movement ie. RUNNING!
ATP can be made/produced from:
- Body Energy Stores (see next slide) such as Glycogen and
Adipose Tissue (or Free Fatty Acids)
- Glucose (Carbohydrate) taken in during exercise
Body Energy Stores of a 155 pound (~70kg) person
300000
275000
250000
Muscle glycogen
Stored Energy (kJ)
Liver glycogen
200000
Adipose tissue (fat)
Muscle Triglycerides (fat)
150000
100000
50000
7000
5500
2000
0
1
Type of Energy
Major producer of ATP - Mitochondria
MITOCHONDRIA
- found within ALL human
cells, especially skeletal muscl.
- “POWERHOUSE” of the
cell- major ATP provider
- INCREASE density of
mitochondria in skeletal muscl
with endurance training
- provides nearly 100% of ATP
while at rest and during easy
‘Aerobic’ exercise
-from Vander, Sherman &
Luciana: Human Physiology
BRIEF MUSCLE ANATOMY OVERVIEW
Electron Microscope Image of Skeletal Muscle
-from Vander, Sherman &
Luciana: Human Physiology
-from Vander, Sherman &
Luciana: Human Physiology
“Classical” Understanding of Muscle Fiber
Types
Slow Twitch
Fast Twitch
or
(RED)
TYPE I
or
TYPE IIa
SO
or
FOG
(Slow-Oxidative)
(WHITE)
or
(Fast Oxidative-Glycolytic)
or
TYPE IIb
FG
(Fast-Glycolytic)
Present Understand of Muscle Fiber Types
-“Dynamic Continuum”-
Slow Twitch
Fast Twitch
(RED)
(WHITE)
TYPE I
TYPE IIa
SO
FOG
(Slow-Oxidative)
(Fast Oxidative-Glycolytic)
TYPE IIb
FG
(Fast-Glycolytic)
**Arrows indicate that fibers can ‘move’ and change according to stimulus
Fiber Type %’s in Different Populations
TYPE I
SO
(Slow-Oxidative)
TYPE IIa
FOG
(Fast Oxidative-Glycolytic)
TYPE IIb
FG
(Fast-Glycolytic)
Population
Untrained
50%
35-40%
10-15%
Endur. Train.
50-60%
40-50%
1-2%
Sprinters
~10-20%
~20-30%
up to 70%
Comparison of Slow vs. Fast Twitch
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Example- Soleus
Longer fibers
Maintenance of posture
Good Endurance, slow
fatigability
Oxidative enzymes
predominate
MORE mitochondria
Greater surrounding
capillarization (RED colour)
MORE glycogen stores
LESS glycogen depletion
during exercise
„
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„
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Example- Triceps
Short fibers
Rapid/Powerfull movemt.
Poor Endurance, rapid
fatigability
Glycolytic Enzymes predominate
LESS mitochondria
Lesser surrounding
capillarization (WHITE colour)
LESS glycogen stores
MORE glycogen depletion
during exercise
-from Martin and Coe: Training Distance Runners
Energy Systems of the Endurance Athlete
- 2. Three ways to provide energy A. C-P system (creatine phosphate)
B. Anaerobic system (Glycolytic or substrate
phosphorylation)
C. Aerobic system (Oxidative phosphorylation)
1. Creatine-Phosphate System
(C-P System)
2. Anaerobic System
(Glycolytic)
3. Aerobic System
(Oxidative)
LACTIC ACID,
CREATINE
-from Martin and Coe: Training Distance Runners
1. Creatine Phosphate (C-P) Energy System
Skeletal Muscl. Anatomy
-see later sheets
MAJOR POINTS:
- Creatine Phosphate
stores in muscle quite
limited
ATP Utilization
-C-P System only good
for very short BURSTS
of energy (~40m - 50m)
ATP Regeneration
- NEED ATP to
regenerate Creatine Phos.
for next burst of energy
Therefore, HARD to
regenerate during exerc.
Creatine Phosphate + ADP
Creatine + ATP
Creatine Kinase (CK)
-from Martin and Coe: Training Distance Runners
2. Anaerobic Energy System (Glycolytic)
GLUCOSE
GLYCOGEN
(Carbohydrate)
(Stored Carbohydrate
in Muscle)
G-6-P
(Glucose-6-Phosphate)
Blood Stream
Muscle Cytoplasm
(Overall Process called Glycolysis)
Muscle Cytoplasm
2 or 3 ATP’s
FAST
LACTIC ACID
PYRUVATE
SLOW
Mitochondria and
AEROBIC Energy
ACEYTL CO-A
= 36 ATP’s
3. Aerobic Energy System (Oxidative)
ADIPOSE STORES
CO2
PYRUVATE
B-Oxidation BREAKS down FATS
and produces Aceytl Co-A
ACETYL CO-A
Inside Muscle
Cytoplasm
Mitochondria
CO2
TCA CYCLE
or KREBS CYCLE
(series of 8 reactions)
CO2
OXIDATIVE PHOSPHORYLATION
H2 O
O2
= 36ATP’s
Anaerobic System
or TCA Cycle
Aerobic System
-from Vander, Sherman &
Luciana: Human Physiology
Anaerobic VS. Aerobic Systems
„
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ANAEROBIC
FUELS:
„
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FAT
CHO
1. ATP Generation for
LONG periods of time at
a decent rate.
2. High ATP production
rate and INCREASES
with endurance training
AEROBIC
FUELS:
„
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Creatine Phosphate
CHO (Glycogen)
1. VERY fast ATP
production
2. Small reserves or
capacity
3. Negative by-products
(ie. Lactic acid)
** BOTH systems “turn-on” during sprinting, it’s just that the aerobic system doesn’t have
time to become optimal and therefore the bulk of the energy produced is through the
anaerobic system.
Energy Systems of the Endurance Athlete
- 3. Exercise intensity drives fuel selection-
Transition from rest to exercise at 110% VO2peak
Transition from rest to exercise at 110% VO2peak
Proportion of energy (%) from fat of
CHO oxidation
Exercise Intensity: CHO vs. FAT
100
90
80
70
60
FAT
50
CHO
40
30
20
10
0
0
20
40
60
80
Exercise Intensity (% of VO2max)
100
adapted from George Brooks
cross-over concept
Fuel Utilization at Different Exercise Intensities
25% VO2max
65% VO2max
(Brisk Walking Pace)
(~Marathon Pace)
85%VO2max
(~5 to 10km race pace)
Fats
Muscle Glycogen
Blood Glucose (sugar)
- 30 min of exercise after an overnight fast:
Romijn,
Romijn, J.A. et al.al.- American Journal of Physiology, E380, 1993.
BREAKDOWN OF THE 3 ENERGY SYSTEMS
-from Martin and Coe: Training Distance Runners
% Energy Contribution
1. Phosphate= Creatine Phosphate System
2. Lactate= Anaerobic System
3. Aerobic= Aerobic System
VO2 MAX= measure of an athletes ability
to transport (cardio-vascular measurement)
oxygen to working muscles.
-from Martin and Coe: Training Distance Runners
TAKE HOME
MESSAGE!
INTENSITY DRIVES FUEL
UTILIZATION/SELECTION….
NOT DURATION!!
Energy Systems of the Endurance Athlete
- 4. Improving physiological components
of running performance -
Developing the Cardiovascular System
All can be IMPROVED with slow easy running
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Cardiovascular system refers to the heart (cardiac) muscle and
the network of vessles that carry blood to and from various
parts of the body.
Function- provide adequate amounts of oxygen to working
muscles and to meet the increases in demands as the runner
becomes more fit. Dependent upon 4 criteria:
„ 1. How powerful the heart is
„ 2. How much oxygen a unit of blood can carry
„ 3. How well the blood flows through the vessels
„ 4. How efficiently blood is diverted from less crucial areas.
The PUMP- (Heart)
„
Cardiac Output = Q
„
Q= SV x HR
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Training INCREASES SV, thus increasing Cardiac
Output
„
SV is increased by increases in blood volume, specifically
the plasma (watery) portion of the blood.
Oxygen-Carrying Capacity of the
Blood
„
The amount of oxygen that blood can carry.
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Blood carried by hemoglobin (IRON containing molecule)
„
Sea Level blood is usually 96%-97% saturated with oxygen
on its hemoglobin.
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ANEMIA
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Endurance training can INCREASE hemoglobin
concentration.
Hemodynamics: Characteristics of Blood
Flow
„
Blood vessel diameter determines blood flow
„
Blood flow INCREASES to exercising muscles and
decreases from areas of lesser need. (This phenomena
improves with endurance training.)
„
Blood viscosity can increases (thicken) during dehydration
due to partial loss of plasma (water) portion of the blood.
Blood shunting
during exercise
-from Martin and Coe: Training Distance Runners
The Running Muscles
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Many changes occur in and around the muscles cells as a
result of training, and relatively slow easy running produces
the desired results.
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Increases in the number, size and density of mitochondria
Increases in the oxidative enzyme activity, which improves the
rate at while delivered oxygen can be processed
Greater perfusion of exerc. Muscles with blood vessels increases
the amount of oxygen that can be provided and the amount of
adverse by-products (CO2 and lactic acid) that can be taken away
Increased ability to store glycogen
Increased ability to use fat as a fuel and SPARE glycogen
Improving Your “Lactate Threshold”
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Runners must be able to work increasingly close to their
maximum oxygen consumption WITHOUT suffering
from high levels of lactic acid.
Lactate accumulation is a function of how much is being
produced by the working muscles and the rate at which it
is being cleared.
Being able to hold down blood-lactate at faster and faster
running speeds is a very desirable trait for distance runners.
The very best way to accomplish THIS is through
threshold OR tempo training.
Improving Aerobic Capacity (VO2
Max)
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The amount of oxygen a runner consumes when
performing a particular workload depends DIRECTLY on
how much oxygen can be delivered to the working
muscles, how well the muscles process the delivered
oxygen, and how easily the muscles deal with the CO2 and
lactate produced during the exercise.
„
A good way to optimize VO2max is to stress the oxygen
delivery system to its limits.
Long interval training is usually optimal. (I.e. Repeat runs
of up to 5-minutes at about 3000m-5000m race pace with
relatively brief recoveries.)
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Developing Speed
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“Sprinters are born, Distance runners are made”- Unknown
NOT necessarily!
ALL muscle fibers can respond to specific training, just
accepted that slow twitch respond better than fast twitch.
The types of training (high intensity-lactic acid type
repeats) that increase speed ALSO increase running
economy the best.
The fact of the matter is this:
“A great kick does you no good if you can’t stay up with
the pace during the BULK of a distance race to use it.
And staying UP means having a high VO2max, a high
lactate threshold and good economy.” -Jack Daniels
Improving Running Economy/Efficiency
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Running economy refers to the amount of oxygen
being consumed relative to the runners body
weight and the corresponding speed at which he or
she is running.
„
More intense repeats improve economy the most
by helping to eliminate unnecessary arm and leg
motion (wasted energy), to recruit the most
desireable motor units at race pace, and to feel
more comfortable at faster speeds.
Thanks…