Energy Transfer During Exercise

1
Energy TransferDuring Exercise

• McArdle, Katch, Katch
• Chapter 6

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Immediate Energy The ATP-PC System

• Immediate rapid supply of energy almost
  exclusively from high energy phosphates ATP and
  PCr within specific muscles.
• How much stored within muscles?

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Immediate Energy phosphagens

• ATP 5 mmol/kg
• PCr 15 mmol/kg
• For 57 kg female (20 kg muscle) 400 mmol total
• For 70 kg male (30 kg muscle) 600 mmol total

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Immediate Energy phosphagens

• Activities that rely almost exclusively on stored
  phosphagens
• Wrestling
• Apparatus routines in gymnastics
• Weight lifting
• Most field events
• Baseball
• Volleyball

5
Short-Term Energy Lactic Acid System

• To continue strenuous exercise beyond a brief
  period, the energy to phosphorylate ADP comes
  from glucose and stored glycogen during anaerobic
  process of glycolysis

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Short-Term Energy Lactic Acid System

• This occurs when oxygen supply is
• Inadequate or
• Oxygen demands exceed oxygen utilization
• Activities powered mainly by lactic acid energy
  system
• Last phase of mile run, 400 m run
• 100 m swim
• Multiple sprint sports ice hockey, field hockey,
  and soccer

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Short-Term Energy Lactic Acid System

• Blood Lactate Accumulation
• Only when lactate removal (Rd lt Ra) is slower
  than lactate production does lactate accumulate.
• During light moderate exercise, aerobic
  metabolism meets energy demands. Non-active
  tissue rapidly oxidize any lactate formed.

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Short-Term Energy Lactic Acid System

• Lactate begins to rise exponentially at about 55
  of healthy untrained persons max VO2.
• Usual explanation is relative tissue hypoxia.
• Point of abrupt increase in blood lactate is
  onset of blood lactate accumulation.

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Short-Term Energy Lactic Acid System

• Blood lactate threshold occurs at higher
  percentage in trained individuals capacity due
  to
• Genetic endowment, e.g. muscle fiber type, or
• Local adaptations that favor production of HLa as
  well as more rapid removal rate at any exercise
  level
• Lactate formed in one part of an active muscle
  can be oxidized by other fibers in same muscle or
  by less active neighboring muscle tissue.

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Short-Term Energy Lactic Acid System

• Ability to generate high lactate concentration in
  maximal exercise increases with specific sprint
  and power training.
• An anaerobically trained athlete can accumulate
  20 to 30 more blood lactate compared to
  untrained subjects.
• Possible reasons
• Increased intramuscular glycogen stores, 20
  increase glycolytic enzymes (PFK), motivation.

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Short-Term Energy Lactic Acid System

• Blood lactate as an Energy Substrate
• Substrate for Gluconeogenesis in liver
• Lactate shuffling between cells supply fuel

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Long Term Energy the Aerobic System

• The use of oxygen by cells is called oxygen
  uptake (VO2).
• Oxygen uptake rises rapidly during the first
  minute of exercise.
• Between 3rd and 4th minute a plateau is reached
  and oxygen uptake remains relatively stable.
• Plateau of oxygen uptake is known as steady rate,
  balance ATP supply demand.

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Long Term Energy the Aerobic System

• Any lactate produced during steady-rate oxidizes
  or reconverts to glucose.
• Many levels of steady-rate in which
• O2 supply O2 demand.
• Functional capacities requires
• Deliver adequate oxygen to muscles
• Process oxygen within muscles

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The Aerobic System

• Oxygen Deficit difference between total oxygen
  consumed during exercise and amount that would
  have been used at steady-rate of aerobic
  metabolism.

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Oxygen Deficit

• Energy provided during the oxygen deficit phase
  represents a predominance of anaerobic energy
  transfer.
• Steady-rate oxygen uptake during light moderate
  intensity exercise is similar for trained
  untrained.
• Trained person reaches steady-rate quicker, has
  smaller O2 deficit.

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Maximum Oxygen Uptake

• The point when VO2 plateaus with additional
  workloads.
• Maximum VO2 indicates an individuals capacity
  for aerobic resynthesis of ATP.
• Additional exercise above the max VO2 can be
  accomplished by anaerobic glycolysis.

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Fast- and Slow-Twitch Fibers
18
The Energy Spectrum

• Relative contribution of aerobic anaerobic
  energy during maximal physical effort.
• Intensity and duration determine the blend.
• Nutrient-related Fatigue severe depletion
  glycogen.

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Oxygen Uptake during Recovery

• Light exercise rapidly attains steady-rate and
  small oxygen deficit.
• Moderate to heavy takes longer to reach
  steady-rate oxygen deficit considerably larger.

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Oxygen Uptake during Recovery

• Four reasons why excess post-exercise oxygen
  consumption (EPOC) takes longer to return to
  baseline following strenuous
• Oxygen deficit is smaller in moderate exercise
• Steady-rate oxygen uptake is achieved versus in
  exhaustive exercise never attained
• Lactic acid accumulates in strenuous exercise
• Body temperature increased considerably more.

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Oxygen Uptake during Recovery

• Traditional Oxygen Debt Theory
• Alactacid oxygen debt restoration of ATP PCr
  depleted during exercise, small portion to reload
  muscle myoglobin hemoglobin fast.
• Lactacid oxygen debt to re-establish original
  glycogen stores by resynthesizing 80 HLa through
  gluconeogenesis (Cori cycle) and to catabolize
  remaining HLa through pyruvic acid (Krebs cycle)
  slower phase.

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Oxygen Uptake during Recovery

• Updated Theory because disprove traditional
  Oxygen Debt Theory.
• EPOC serves to replenish high-energy phosphates
  and some to resynthesize a portion of lactate to
  glycogen.
• Significant portion EPOC attributed to
  thermogenic boost that stimulates metabolism
  (Q10).
• Other factors EPOC 10 reloads blood O2 2-5
  restores O2 in body fluids, including myoglobin
  all systems increased O2 need in recovery due to
  effects of epinephrine, norepinephrine, and
  thyroxine.

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Oxygen Uptake during Recovery

• Time frame for lactate removal post-exercise
• Mass action effect rate proportional to amount
  of substrate product present
• Passive or Active Recovery
• Optimum recovery steady-rate exercise passive
• Optimum recovery non-steady rate active

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Oxygen Uptake during Recovery

• Intermittent Exercise interval training
• Major advantage of interval training enable
  performance of large amounts of exhaustive
  exercise lower HLa
• Exercise Recovery Ratio
• 13 ratio overloads immediate energy system
• 12 ratio to train short-term glycolytic system
• 11 ratio to train long-term aerobic system

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Illustration References

• McArdle, William D., Frank I. Katch, and Victor
  L. Katch. 2000. Essentials of Exercise
  Physiology 2nd ed. Image Collection. Lippincott
  Williams Wilkins.
• Plowman, Sharon A. and Denise L. Smith. 1998.
  Digital Image Archive for Exercise Physiology.
  Allyn Bacon.