Exercise Metabolism

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Exercise Metabolism

• Chapter 4
• pp 53-68

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1. Rest-to-Exercise Anaerobic
anaerobic
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2. Rest-to-Exercise Aerobic

• Example....
• Assume standing requires 15 ATP and 0.4
  liters/min of oxygen
• Assume running at 6 mph requires 100 ATP and 1.5
  liter/min of oxygen
• A person can go from standing to running 6 mph in
  a mater of seconds.
• But, it takes 2-3 minutes for the oxygen
  requirement to go from 0.4 to 1.5 liters/min
• Where does the ATP needed to run 6 m.p.h come
  from until adequate oxygen can be supplied?

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Rest-to-Exercise The Oxygen Deficit
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3. Recovery

• What needs to happen in recovery?
• ATP-PCr system
• P Cr energy ? PCr
• Glycolysis?
• Lactic acid removal from muscle fiber

Where does the energy comes from?
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Lactic Acid Removal

• Where?
• Heart and Type I Muscle Fibers
• How?
• Lactic acid ? Pyruvic Acid
• Pyruvic Acid ? Acetyl Co-A
• Acetyl Co-A ? Krebs Cycle (aerobic system)

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Lactate as a Fuel During Exercise

• Slow twitch muscle fibers
• Heart muscle
• Liver via the Cori cycle

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E.P.O.C
What does E.P.O.C. stand for note oxygen
consumption energy What contributes to the
excess oxygen consumption?
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E.P.O.C.
(Used as a fuel)
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4. Prolonged Aerobic Exercise

• Aerobic energy requires O2
• oxygen demand
• O2 transported via cardioplumonary system
• oxygen supply

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Prolonged Aerobic Exercise

• Deficit O2 supply lt O2 demand
• Steady State Exercise
• O2 supply O2 demand
• Heart rate? Breathing rate?

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5. Measurement of Aerobic Energy/Performance

• Maximal oxygen uptake
• Lactate threshold

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Oxygen Uptake
79 N 20.97 O2 0.03 CO2
Ventilation (Liters of air per minute)
79 N 17 O2 4 CO2
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Oxygen Uptake (VO2)
79 N 20.97 O2 0.03 CO2
VO2
79 N 17 O2 4 CO2
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Oxygen Uptake (VO2)

• What does it measure?
• How is it expressed?
• VO2 ml/kg/min
• VO2 liters/min

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Maximum Oxygen Uptake (VO2max)
What is VO2max? What does it represent?
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VO2max Values
Percentile 20-29 30-39 40-49 50-59 60
Men
90 55.1 52.1 50.6 49.0 44.2
50 44.2 42.6 41.0 37.8 34.6
10 34.5 33.0 31.4 29.9 26.7
Women
90 49.0 45.8 42.6 37.8 34.6
50 37.8 34.6 33.0 29.9 26.7
10 28.4 26.7 25.1 21.9 20.3
Source ACSM
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General Population, Female, Aged 20-29
35-43 ml/kg/min General Population, Male,
Aged 20-29 44-51 US College Track, Male
57.4 College Students, Male 44.6
Highest Recorded Female (Cross-Country Skier)
74 Highest Recorded Male (Cross-Country
Skier) 94
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VO2max
FYI
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Bjørn Dæhlie 96 ml/kg/min
FYI
Steve Prefontaine 84 ml/kg/min
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Lactic Acid Production

• What happens to pyruvate?
• If adequate oxygen
• pyruvate to acetyl CoA
• hydrogen to H2O
• If inadequate oxygen
• pyruvate and hydrogen to lactic acid
• What happens to lactic acid levels as the
  exercise intensity increases?

1.
2.
2.
1.
Acetyl-CoA
Hydrogen
Mitochondria (Krebs cycle Electron Transport
Chain)
Oxygen
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Lactate Threshold
Lactate (mmols)
Light to Moderate Exercise. LA removed
Heavy Exercise. LA accumulates
3 4 5 6 7 8 9 10
Speed (mph)
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Lactate Threshold
VO2max

• The Lactate Threshold typically occurs between
  50-85 of Vo2max
• What is significant about the intensity level at
  the lactate threshold?

3 4 5 6
7 8 9 10 Running Speed
3 4 5 6
7 8 9 10 Running Speed
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7. Fuel Utilization During Exercise
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Measuring Fuel Utilization During Exercise

• Respiratory exchange ratio (RER or R)
• R VCO2 / VO2
• Fat (palmitic acid) C16H32O2
• C16H32O2 23O2 ? 16CO2 16H2O ATP
• R VCO2/VO2 16 CO2 / 23O2 0.70
• Glucose C6H12O6
• C6H12O6 6O2 ? 6CO2 6H2O ATP
• R VCO2/VO2 6 CO2 / 6O2 1.00

It takes more O2 to burn fats so the R value for
fats will be lower.
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Fuel Utilization During Exercise

• Carbohydrates and Fats (very little Protein)

R Fat Carbs
0.70 99 1
0.75 83 17
0.80 67 33
0.85 50 50
0.90 33 67
0.95 17 83
1.00 1 99
Resting
Low Intensity
High Intensity
Max. Intensity
High Intensity
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Fuel Utilization During Exercise
Which fuel is used more as the exercise INTENSITY
increases? Why the shift towards carbohydrates?
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Fuel Utilization During Exercise
What fuel is used more as the exercise DURATION
increases? Why the shift towards fats?
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8. Fuels for Exercise
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Sources of Carbohydrate During Exercise

• Muscle glycogen
• Liver glycogen
• Total of about 2,000 kcals (1.5-2 hrs)
• Systems
• Glycolysis
• Lactic acid
• Aerobic

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Sources of Fat During Exercise

• Adipose tissue
• Triglycerides to fatty acids
• Muscle cells
• Total of 50,000-100,000 kcals
• System aerobic

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Protein for Energy During Exercise

• Skeletal muscle
• Amino acids and the Cori cycle
• Why is protein not an optimal fuel source?

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The Glucose-Alanine Cycle
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Gluconeogensis

• The Cori cycle and the Glucose-Alanine cycle
• What do they have in common?
• Gluconeogensis

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Energy Related Fatigue

• Glycogen depletion
• Hypoglycemia