Transcript Energy Systems

The Scientific Basis of
Aerobic Fitness
Chapter 3
Overview of Energy Metabolism
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large nutrients digested into smaller, usable fuels
– carbohydrates  glucose
– fats (triglycerides)  fatty acids
– proteins  amino acids
blood delivers fuels to muscle which transforms them
into ATP (adenosine triphosphate)
ATP is the universal “currency” used by tissues for
energy needs
food + O2  ATP + CO2 + H2O + heat
Energy Systems: Fuels
Carbohydrates
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primary form is glucose
transported to muscle (and other tissues) via
blood
stored in liver and muscle as glycogen
ATP produced more quickly from CHO than
from fats or proteins
CHO stores can be depleted
Energy Systems: Fuels
Fats (triglycerides)
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stored in adipose tissue and in muscle
muscle uses fatty acids for fuel
produce ATP more slowly than CHO
during rest, provides >½ the ATP, but little
during intense exercise
fat stores not depletable
Energy Systems: Fuels
Proteins
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split into amino acids in gut, absorbed, and
transported by blood
1º role is providing building blocks for metabolic
functions and tissue building
provides 5-15% of fuel for ATP production
Overview of Energy Metabolism
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muscles have small ATP storage capacity
3 energy systems produce ATP
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aerobic – 1º system for endurance events
anaerobic – 1º system for speed events
“immediate” – 1º system for power events
systems may work simultaneously
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depends upon exercise intensity and duration
Interaction of Energy Systems
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Aerobic system takes 2-3 min to fully activate
Anaerobic glycolysis takes ~5 s to fully
activate
Immediate system can provide ATP
immediately
Mitochondria
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not a bean shape, rather a long reticulum
aerobic metabolism of CHO, fats, and
proteins occur entirely in mitochondria
all substrates formed into acetyl Coenzyme
A before entering Kreb’s cycle
Anaerobic vs. Aerobic
Energy Systems
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Anaerobic
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ATP-CP : 10 sec. Or less
Glycolysis : Few minutes
Aerobic
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Krebs cycle
Electron Transport Chain
2 minutes +
Energy Transfer Systems and Exercise
100%
% Capacity of Energy System
Anaerobic
Glycolysis
Aerobic
Energy
System
ATP - CP
10 sec
30 sec
2 min
5 min +
Exercise Energy Metabolism During Exercise
At onset of exercise,
three systems are used
continuously, though
contribution of the three
systems change with
time.
Anaerobic Conditioning
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Phosphate Pool
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All out bursts of 5-10 seconds will significantly deplete
the ATP-CP system.
Very little LA produced (< 10-15 sec. Bursts)
Rest periods of 30 – 60 seconds will provide complete
recovery ([ATP-CP] back to normal)
High intensity interval training
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Increases [ATP-CP]
Facilitates neuromuscular adaptations to the RATE and
PATTERN of the movement.
Anaerobic Conditioning
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Glycolysis / Lactic Acid System
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ALL OUT effort beyond 10 seconds (usually 1 min.)
Very taxing on athlete (psychologically and physically)
Recover twice as long exercise bout
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2-1 ratio
Results in “stacking” of LA  Increasingly high [LA]
Full recovery ([LA] back to baseline) may take hours.
ONLY occurs in muscles overloaded!
Aerobic Energy Production
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Steady state exercise beyond 3-4 minutes is
powered mainly by Aerobic Glycolysis
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Pyruvic Acid & Lipid/Protein fragments enter Kreb’s
Cycle and ETC. Energy produced resynthesizes
ATP.
As long as sufficient O2 is available to meet energy
needs, fatigue is minimal and exercise continues!
The intensity that elicits anaerobic metabolism is
dependant on the person’s aerobic capacity
Anaerobic
Glucose
Energy
ATP
H+
Pyruvic Acid (2)
Lactic Acid (2)
Inter Cellular Fluid
Fatty
Acids
Amino
Acids
CO2
CO2
&
H+
Mitochondria
Aerobic
Acetyl Co-A (2)
Krebs
Cycle
Energy
H+
ATP
To ETC
Energy
ATP
Krebs
CO2
Cycle
H+
2H+ +
--
O
Electron
Transport
Chain
= H2O
ATP
Aerobic Capacity
 Ability
of the Cardiovascular
system to deliver oxygen rich
blood to body tissues.
 Muscles ability to process and
utilize oxygen to produce
energy.
Evaluating Aerobic Capacity
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Measure
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VO2max via spirometry / graded exercise stress
test
Estimate
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Sub-maximal graded exercise test
Step test
 Based
on the fact that individuals with higher SV
will recover faster
 Recovery HR will be lower in individuals w/ higher
VO2max
Heart Rate Response to
Step Test
180
160
140
Sedentary
120
Trained
100
Elite Athlete
80
60
40
20
Rest
Begin
Exercise
1 min
2 min
End
Exercise
1 min
2min
Factors That Effect Aerobic
Conditioning
 Initial
level of cardiovascular fitness
 Frequency of training
 Duration of training
 Intensity of training
 Specificity of training
Initial Fitness Level
Lower initial fitness level allows more room
for improvement
 Generally “average” individual can expect
5-25% improvement w/ 12 weeks of
training
 Everyone has GENETIC Limit
 Some people are genetically more gifted
and/or respond better to training
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Frequency of Training
 Generally
recommended: at least 3
X’s/week
 Training 4 or more days per week
results in only small increases in
VO2max
 Weight control: 6 or 7 days/week
recommended
Duration of Training
 30
minutes of continuous
exercise is recommended
 Discontinuous exercise of
greater intensity has shown
comparable results
Continuous vs. Discontinuous Exercise
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Continuous (Long Slow Distance)
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70-90% of HR max
Less taxing on individual
Interval Training
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Repetitive exercise intervals separated by rest
intervals
Exercise Interval: 90% HR max
Rest interval: 3X’s as long as exercise (3:1
ratio)
Training Intensity
Most critical factor in training
 May be expressed as:
% of VO2max
Heart rate or % of maximum HR
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METS
Rating of Perceived Exertion (RPE)
Calories per unit time
Training Intensity
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Threshold for aerobic improvement
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At least 50-55% of VO2max
70%+ of age predicted max HR (220-age)
Often referred to as “conversational exercise”
Overload will eventually become average
activity
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Must increase intensity / duration to continue
improvement in CV endurance
ACSM
Recommendations
At least 3X’s per week
 30 – 60 minutes
 Continuous, large muscle mass
exercises
 Expend at least 300kcals per session
 70% of age predicted max HR
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Guidelines
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Start slowly
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Warm Up (50-60% Max HR)
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Much higher risk of injury before adaptation occurs
 temp. of & blood flow to muscle
Gentle stretching
Dress for the weather
Cool Down
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Increases LA removal
Decreases pooling of blood in veins
Gentle stretching
Why does blood lactate increase
during heavy exercise?
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lactate appearance
exceeds lactate
removal
evidence does not point
to muscle hypoxia
FT recruitment
epinephrine release
Basal Metabolic Rate
Your basal metabolic rate, or BMR, is the minimum calorific
requirement needed to sustain life in a resting individual. It can be
looked at as being the amount of energy (measured in calories)
expended by the body to remain in bed asleep all day!
BMR can be responsible for burning up to 70% of the total calories
expended, but this figure varies due to different factors (see below).
Calories are burned by bodily processes such as respiration, the
pumping of blood around the body and maintenance of body
temperature. Obviously the body will burn more calories on top of those
burned due to BMR.
Components of Daily Energy Expenditure
Thermic effect
of feeding
8%
Energy expenditure of
physical activity
17%
Resting energy
expenditure
8%
32%
75%
Sedentary Person
(1800 kcal/d)
Segal KR et al. Am J Clin Nutr. 1984;40:995-1000.
60%
Physically Active Person
(2200 kcal/d)
Slide Source: www.obesityonline.org
Energy needed for activity
Calorimetry gives energy needed for various levels
of activity. Energy expenditures above basal:
•Eating, reading 0.4 Cal/kg-h
•Doing laundry 1.3
•Cello playing 1.3
•Walking slowly 2.0
•Walking 4 mph 3.4
•Swimming 2 mph 7.9
•Crew race 16.0
Basal metabolic rate
•It takes energy just to stay alive.
Basal metabolic rate, or BMR
•For warm-blooded animals, most energy used
to maintain body temperature.
•Human BMR: 1.0 Cal/kg-h
Example: m = 70 kg, 24 hour day
•Basal metabolism = 1.0 Cal/kg-h * 70 kg * 24 h/day
=1680 Cal/day
This doesn’t account for any activity.
Figuring total caloric needs: One 75 kg person’s day
Basal metabolism
1.0 Cal/kg-h * 24 h * 75 kg = 1800 Cal
Reading, writing, talking, eating, 12.5 h
0.4 Cal/kg-h * 12.5 h * 75 kg = 375 Cal
Walking slowly, 1 h
2.0 Cal/kg-h * 1 h * 75 kg = 150 Cal
Playing cello, 1.25 h
1.3 Cal/kg-h * 1.25 h * 75 kg = 120 Cal
Energy needed for digestion
2500 Cal consumed * 8% = 200 Cal
Total needs: 2645 Cal
Total daily energy expenditure
Solving for moderate exercise activity total daily energy expenditure (TDEE)
Harris-Benedict
Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) - (6.8 X age)
Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) - (4.7 X
age)
Note: 1 inch = 2.54 cm.
1 kilogram = 2.2 lbs.
Example:
You are female
You are 30 yrs old
You are 5' 6 " tall (167.6 cm)
You weigh 120 lbs. (54.5 kilos)
Your BMR = 655 + 523 + 302 - 141 = 1339
calories/day
Activity multiplier
Sedentary = BMR X 1.2 (little or no exercise, desk job)
Lightly active = BMR X 1.375 (light exercise/sports 1-3 days/wk)
Mod. active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)
Very active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)
Extr. active = BMR X 1.9 (hard daily exercise/sports & physical job or 2X day
training, i.e marathon, contest etc.)
Example:
Your BMR is 1339 calories per day
Your activity level is moderately active (work out 3-4 times per week)
Your activity factor is 1.55
Your TDEE = 1.55 X 1339 = 2075 calories/day
Determine the energy cost: ______________________
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Chapter 9
Reminders for Monday, September 21st
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Quiz 3: Vo2 Max, Aerobic Field Tests (Chapter
2), and The Scientific Basis of Aerobic Fitness
(Chapter 3) and lecture slides
Meet at the football stadium for
cardiorespiratory tests