Energy Transfer During Exercise McArdle, Katch, & Katch Chapter 6

Energy TransferEnergy TransferDuring ExerciseDuring Exercise

McArdle, Katch, & KatchMcArdle, Katch, & Katch

Chapter 6Chapter 6

Immediate Energy: The ATP-PC Immediate Energy: The ATP-PC SystemSystem

Immediate & rapid Immediate & rapid supply of energy supply of energy almost exclusively almost exclusively from high energy from high energy phosphates ATP and phosphates ATP and PCr within specific PCr within specific muscles.muscles.

How much stored How much stored within muscles?within muscles?

Immediate Energy: phosphagensImmediate Energy: phosphagens

ATP = 5 mmol/kgATP = 5 mmol/kg

PCr = 15 mmol/kgPCr = 15 mmol/kg

For 57 kg female (20 kg muscle) = 400 mmol totalFor 57 kg female (20 kg muscle) = 400 mmol total

For 70 kg male (30 kg muscle) = 600 mmol totalFor 70 kg male (30 kg muscle) = 600 mmol total

Brisk WalkBrisk Walk Slow JogSlow Jog All-out SprintAll-out Sprint

1 minute1 minute 20 – 30 sec.20 – 30 sec. 6 – 8 seconds6 – 8 seconds

Immediate Energy: phosphagensImmediate Energy: phosphagens

Activities that rely almost exclusively on Activities that rely almost exclusively on stored phosphagens:stored phosphagens: WrestlingWrestling Apparatus routines in gymnasticsApparatus routines in gymnastics Weight liftingWeight lifting Most field eventsMost field events BaseballBaseball VolleyballVolleyball

Short-Term Energy: Lactic Acid Short-Term Energy: Lactic Acid SystemSystem

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


This occurs when oxygen supply isThis occurs when oxygen supply is Inadequate orInadequate or Oxygen demands exceed oxygen utilizationOxygen demands exceed oxygen utilization

Activities powered mainly by lactic acid Activities powered mainly by lactic acid energy systemenergy system Last phase of mile run, 400 m runLast phase of mile run, 400 m run 100 m swim100 m swim Multiple sprint sports: ice hockey, field Multiple sprint sports: ice hockey, field

hockey, and soccerhockey, and soccer


Blood Lactate AccumulationBlood Lactate Accumulation

Only when lactate removal Only when lactate removal (L(Ldd < L < Laa) is slower than ) is slower than

lactate production does lactate production does lactate accumulate.lactate accumulate.

During light & moderate During light & moderate exercise, aerobic exercise, aerobic metabolism meets energy metabolism meets energy demands. Non-active demands. Non-active tissue rapidly oxidize any tissue rapidly oxidize any lactate formed.lactate formed.


Lactate begins to rise Lactate begins to rise exponentially at about exponentially at about 55%55% of healthy untrained of healthy untrained person’s max VOperson’s max VO22..

Usual explanation is Usual explanation is relative tissue hypoxia.relative tissue hypoxia.

Point of abrupt increase Point of abrupt increase in blood lactate is in blood lactate is onset onset of blood lactate of blood lactate accumulationaccumulation..


Blood lactate threshold occurs at higher Blood lactate threshold occurs at higher percentage in trained individual’s capacity percentage in trained individual’s capacity due to:due to: Genetic endowment, e.g. muscle fiber type, orGenetic endowment, e.g. muscle fiber type, or Local adaptations that favor less production of Local adaptations that favor less production of

HLa and more rapid removal rate. HLa and more rapid removal rate. Endurance Endurance trg.trg. extends exercise intensity before OBLA. extends exercise intensity before OBLA.

Lactate formed in one part of an active Lactate formed in one part of an active muscle can be oxidized by other fibers in muscle can be oxidized by other fibers in same muscle or by less active neighboring same muscle or by less active neighboring muscle tissue.muscle tissue.


Blood lactate as an Energy SubstrateBlood lactate as an Energy Substrate Substrate for Gluconeogenesis in liverSubstrate for Gluconeogenesis in liver Lactate shuttling between cells – supply fuelLactate shuttling between cells – supply fuel


Ability to generate high lactate Ability to generate high lactate concentration in maximal exercise concentration in maximal exercise increases with specific sprint and power increases with specific sprint and power training.training.An anaerobically trained athlete can An anaerobically trained athlete can accumulate 20 to 30% more blood lactate accumulate 20 to 30% more blood lactate compared to untrained subjects.compared to untrained subjects.Possible reasons:Possible reasons: Increased intramuscular glycogen stores, Increased intramuscular glycogen stores,

20% increase glycolytic enzymes, motivation.20% increase glycolytic enzymes, motivation.

Long Term Energy: the Aerobic Long Term Energy: the Aerobic SystemSystem

The use of oxygen by The use of oxygen by cells is called cells is called oxygen oxygen uptake (VOuptake (VO22).).

Oxygen uptake rises Oxygen uptake rises rapidly during the rapidly during the firstfirst minute of exercise.minute of exercise.

Between 3Between 3rdrd and 4 and 4thth minute a minute a plateauplateau is is reached and VOreached and VO22 remains remains

relatively stable.relatively stable.

Plateau of oxygen uptake Plateau of oxygen uptake is known as is known as steady rate.steady rate.

Long Term Energy: Aerobic SystemLong Term Energy: Aerobic System

Steady-rate is balance of energy required and ATP produced.Steady-rate is balance of energy required and ATP produced.

Any lactate produced during steady-rate oxidizes or Any lactate produced during steady-rate oxidizes or reconverts to glucose.reconverts to glucose.

Many levels of steady-rate in which: OMany levels of steady-rate in which: O22 supply = O supply = O22 demand. demand.

Oxygen supply requiresOxygen supply requires1.1. Deliver adequate oxygen to musclesDeliver adequate oxygen to muscles

2.2. Process oxygen within musclesProcess oxygen within muscles

The Aerobic SystemThe Aerobic System

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

Oxygen DeficitOxygen Deficit

Energy provided during the Energy provided during the oxygen deficit phase represents a phase represents a predominance of anaerobic energy transfer from stored predominance of anaerobic energy transfer from stored intramuscular phosphagens plus rapid glycolytic reactions.intramuscular phosphagens plus rapid glycolytic reactions.Steady-rate oxygen uptake during light & moderate intensity Steady-rate oxygen uptake during light & moderate intensity exercise is similar for trained & untrained.exercise is similar for trained & untrained.TrainedTrained person reaches steady-rate person reaches steady-rate quickerquicker, has , has smaller smaller oxygen deficitoxygen deficit..

Maximum Oxygen UptakeMaximum Oxygen Uptake

The point when VOThe point when VO22 plateaus with plateaus with additional workloadsadditional workloads..

Maximum VOMaximum VO22 indicates an individual’s capacity for indicates an individual’s capacity for

aerobic resynthesis of ATP.aerobic resynthesis of ATP.

Additional exercise above the max VOAdditional exercise above the max VO22 can be can be

accomplished by anaerobic glycolysis.accomplished by anaerobic glycolysis.

Fast- and Slow-Twitch FibersFast- and Slow-Twitch Fibers

Fast Twitch Fibers (II)Fast Twitch Fibers (II) Slow Twitch Fibers (I)Slow Twitch Fibers (I)

Fast Contraction SpeedFast Contraction Speed Half as Fast as FTHalf as Fast as FT

High Anaerobic CapacityHigh Anaerobic Capacity High Aerobic Capacity: High Aerobic Capacity: mitochondrial density, mitochondrial density, aerobic enzymesaerobic enzymes

The Energy SpectrumThe Energy Spectrum

Relative contribution of Relative contribution of aerobic & anaerobic aerobic & anaerobic energy during maximal energy during maximal physical effort.physical effort.

Intensity and duration Intensity and duration determine the blend.determine the blend.

Nutrient-related Nutrient-related Fatigue: severe Fatigue: severe depletion glycogen.depletion glycogen.

Oxygen Uptake during RecoveryOxygen Uptake during Recovery

A.A. Light aerobic exercise Light aerobic exercise rapidly attains steady-rate rapidly attains steady-rate with small oxygen deficit.with small oxygen deficit.

B.B. Moderate to heavy Moderate to heavy aerobic takes longer to aerobic takes longer to reach steady-rate and reach steady-rate and oxygen deficit oxygen deficit considerably larger.considerably larger.

C.C. Maximal exercise Maximal exercise (aerobic-anaerobic) VO(aerobic-anaerobic) VO22

plateaus without matching plateaus without matching energy requirement.energy requirement.


Four reasons why Four reasons why eexcess xcess ppost-exercise ost-exercise ooxygen xygen cconsumption (onsumption (EPOCEPOC) takes longer ) takes longer to return to baseline following strenuousto return to baseline following strenuous

1.1. Oxygen deficit is smaller in moderate exerciseOxygen deficit is smaller in moderate exercise

2.2. Steady-rate oxygen uptake is achieved versus Steady-rate oxygen uptake is achieved versus in exhaustive exercise never attainedin exhaustive exercise never attained

3.3. Lactic acid accumulates in strenuous exerciseLactic acid accumulates in strenuous exercise

4.4. Body temperature increased considerably Body temperature increased considerably more.more.


Traditional “Oxygen Debt” TheoryTraditional “Oxygen Debt” Theory Alactacid oxygen debt: restoration of ATP & Alactacid oxygen debt: restoration of ATP &

PCr depleted during exercise, small portion to PCr depleted during exercise, small portion to reload muscle myoglobin & hemoglobin reload muscle myoglobin & hemoglobin [fast][fast]..

Lactacid oxygen debt: to re-establish original Lactacid oxygen debt: to re-establish original glycogen stores by resynthesizing 80% HLa glycogen stores by resynthesizing 80% HLa through gluconeogenesis (Cori cycle) and to through gluconeogenesis (Cori cycle) and to catabolize remaining HLa through pyruvic catabolize remaining HLa through pyruvic acid (Kreb’s cycle) acid (Kreb’s cycle) [slower phase][slower phase]..

Deficit and EPOCDeficit and EPOC


Updated Theory because disprove Updated Theory because disprove traditional Oxygen Debt Theory.traditional Oxygen Debt Theory. EPOC serves to replenish high-energy phosphates EPOC serves to replenish high-energy phosphates

and some to resynthesize a portion of lactate to and some to resynthesize a portion of lactate to glycogen.glycogen.

Significant portion EPOC attributed to Significant portion EPOC attributed to thermogenic thermogenic boost that stimulates metabolism (Qboost that stimulates metabolism (Q1010))..

Other factors EPOC: 10% reloads blood OOther factors EPOC: 10% reloads blood O2;2; 2-5% 2-5%

restores Orestores O22 in body fluids, including myoglobin; all in body fluids, including myoglobin; all

systems increased Osystems increased O22 need in recovery due to effects need in recovery due to effects

of epinephrine, norepinephrine, and thyroxine.of epinephrine, norepinephrine, and thyroxine.


Time frame for lactate Time frame for lactate removal post-exerciseremoval post-exerciseMass action effect: rate Mass action effect: rate proportional to amount of proportional to amount of substrate & product substrate & product presentpresent

Passive or Active Passive or Active RecoveryRecovery

Optimum recovery steady-Optimum recovery steady-rate exercise: rate exercise: passivepassive

Optimum recovery non-Optimum recovery non-steady rate: steady rate: activeactive


Intermittent Exercise: interval trainingIntermittent Exercise: interval training

Major advantage of interval training: Major advantage of interval training: enable performance of large amounts of enable performance of large amounts of exhaustive exercise & lower HLaexhaustive exercise & lower HLa

Exercise: Recovery RatioExercise: Recovery Ratio 1:3 ratio overloads immediate energy system1:3 ratio overloads immediate energy system 1:2 ratio to train short-term glycolytic system1:2 ratio to train short-term glycolytic system 1:1 ratio to train long-term aerobic system1:1 ratio to train long-term aerobic system

Illustration ReferencesIllustration References

Axen and Axen. 2001. Axen and Axen. 2001. Illustrated Principles of Illustrated Principles of Exercise PhysiologyExercise Physiology. Prentice Hall.. Prentice Hall.

McArdle, William D., Frank I. Katch, and McArdle, William D., Frank I. Katch, and Victor L. Katch. 2011. Victor L. Katch. 2011. Essentials of Exercise Essentials of Exercise PhysiologyPhysiology 4 4thth ed. Image Collection. ed. Image Collection. Lippincott Williams & Wilkins.Lippincott Williams & Wilkins.

Plowman, Sharon A. and Denise L. Smith. Plowman, Sharon A. and Denise L. Smith. 1998. Digital Image Archive for 1998. Digital Image Archive for Exercise Exercise PhysiologyPhysiology. Allyn & Bacon.. Allyn & Bacon.

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Energy Transfer During Exercise McArdle, Katch, & Katch Chapter 6