GycogenolysisGycogenolysis

catabolism of glycogen moleculecatabolism of glycogen molecule glycogen is polymer of glucose unitsglycogen is polymer of glucose units form a pin-wheel-like structure around a form a pin-wheel-like structure around a

foundation protein, P-glycogeninfoundation protein, P-glycogenin linkages at C1-C4 or some C1-C6linkages at C1-C4 or some C1-C6

Approx. 80% of carbon for Approx. 80% of carbon for Glycolysis from glycogen, not Glycolysis from glycogen, not

glucoseglucose

Breakdown is dependant on Breakdown is dependant on activity of enzyme activity of enzyme

phosphorylase, hydrolyzes the phosphorylase, hydrolyzes the C1-C4 linkagesC1-C4 linkages

Other enzyme, de-branching Other enzyme, de-branching enzyme hydrolyzes the C1-C6 enzyme hydrolyzes the C1-C6

or side linkagesor side linkages

Phosphorylase is controlled by Phosphorylase is controlled by two mechanisms:two mechanisms:

hormonally mediated: extracellular action of hormonally mediated: extracellular action of epi on intracellular action of cAMP epi on intracellular action of cAMP (intracellular hormone)(intracellular hormone)

too slow during the onset of heavy exercisetoo slow during the onset of heavy exercise mechanism mediated by Camechanism mediated by Ca2+2+, from the SR, , from the SR,

parallel mechanismparallel mechanism

Hormonally mediated cAMPHormonally mediated cAMP

amplifies the local Caamplifies the local Ca2+ 2+ -- mediated process -- mediated process in active musclein active muscle

mobilizes glycogen in inactive muscle to mobilizes glycogen in inactive muscle to provide lactate as glycogenic precursorprovide lactate as glycogenic precursor

Phosphorylase is converted Phosphorylase is converted from phosphorylase b from phosphorylase b

(inactive) to phosphorylase a (inactive) to phosphorylase a (active)(active)

During exercise, AMP During exercise, AMP increases, helping to minimize increases, helping to minimize

the conversion from the conversion from phosphorylase a to bphosphorylase a to b

RQ vs RERRQ vs RER

both are VOboth are VO22 consumed/VCO consumed/VCO22 produced produced

RQ: at the cell levelRQ: at the cell level RER: at the mouthRER: at the mouth

RQ = RER, except at the RQ = RER, except at the onset and offset of exercise, onset and offset of exercise,

due to body COdue to body CO22 storage storage

changeschanges

Protein RQ = 0.83Protein RQ = 0.83

CHO RQ = 1.00CHO RQ = 1.00

Fat RQ = 0.70Fat RQ = 0.70

Anaerobic metabolism is not Anaerobic metabolism is not well understood compared to well understood compared to

aerobic metabolismaerobic metabolism

Anaerobic: three misconceptionsAnaerobic: three misconceptions

anaerobic metabolism during exercise anaerobic metabolism during exercise results in “Oresults in “O22 debt” debt”

lactic acid is a “dead-end” metabolite, only lactic acid is a “dead-end” metabolite, only formed, not removed during exerciseformed, not removed during exercise

elevation of lactic acid levels during exercise elevation of lactic acid levels during exercise represents anaerobiosis (Orepresents anaerobiosis (O22 insufficiency) insufficiency)

Two assumptions about indirect Two assumptions about indirect calorimetrycalorimetry

ATP-PC stores are maintained, ATP comes ATP-PC stores are maintained, ATP comes from respirationfrom respiration

protein catabolism is insignificant during protein catabolism is insignificant during exerciseexercise– invalid, but necessaryinvalid, but necessary

Steady state/steady rate: Steady state/steady rate:

oxygen consumption is relatively constant, oxygen consumption is relatively constant, directly proportional to the constant submax directly proportional to the constant submax work loadwork load

Rate of appearance (RRate of appearance (Raa) and ) and

Rate of disappearance (RRate of disappearance (Rdd) of ) of

lactate, glucose, etc.lactate, glucose, etc.•Mild to moderate intensity exercise, lot of Mild to moderate intensity exercise, lot of lactate is formedlactate is formed•High intensity exercise, more lactate is High intensity exercise, more lactate is produced and appears in the bloodproduced and appears in the blood•Muscle is a consumer of lactateMuscle is a consumer of lactate

Misconception #1) OMisconception #1) O22

consumption during exercise consumption during exercise is insufficient to meet the is insufficient to meet the demands of exercise; creating demands of exercise; creating a debta debt

body “borrows” from energy reserves or credits body “borrows” from energy reserves or credits after exercise, pay back creditsafter exercise, pay back credits the extra Othe extra O2 2 consumed during recovery, above consumed during recovery, above

resting Oresting O22 was the O was the O22 debt debt

Cease exercise: HR, breathing, etc. still Cease exercise: HR, breathing, etc. still elevatedelevated

B/c oxygen cost is still higher after exercise B/c oxygen cost is still higher after exercise compared to rest, originally why thought is was compared to rest, originally why thought is was “debt”“debt”

Excess Postexercise Oxygen Excess Postexercise Oxygen Consumption (EPOC)Consumption (EPOC)

better descriptor of oxygen consumption better descriptor of oxygen consumption during recoveryduring recovery

EPOC due toEPOC due to

TemperatureTemperature HormonesHormones increased energy cost of ventilationincreased energy cost of ventilation increased energy cost of HRincreased energy cost of HR

Two phases of recovery: fast Two phases of recovery: fast and slowand slow

Much of work is based on Much of work is based on tracer methodology: infuse tracer methodology: infuse radio-labeled radio-labeled 1414C and C and 33H H

tracerstracers

Misconception #2) Lactate levels Misconception #2) Lactate levels lower in trained for both easy and lower in trained for both easy and

hard exercisehard exercise

lower lactate in TR concealed fact that LA lower lactate in TR concealed fact that LA production was same in TR and UNTRproduction was same in TR and UNTR

TR improve lactate clearanceTR improve lactate clearance

Anaerobic Threshold:Anaerobic Threshold:

increase in intensityincrease in intensity oxygen consumption increases linearlyoxygen consumption increases linearly but lactate levels not change until 60% of but lactate levels not change until 60% of

maxmax

marked inflection point, often marked inflection point, often termed “anaerobic threshold” AT, termed “anaerobic threshold” AT,

or “lactate threshold” LTor “lactate threshold” LT

Linkages between insufficient oxygen Linkages between insufficient oxygen (anaerobiosis)(anaerobiosis)

lactate productionlactate production pulmonary ventilationpulmonary ventilation

Lactic acid, HLA is strong acid:Lactic acid, HLA is strong acid:

can readily dissociate a proton (Hcan readily dissociate a proton (H++ ion) ion) HLA must be buffered:HLA must be buffered: in blood, bicarbonate (HCOin blood, bicarbonate (HCO33

--)- carbonic acid )- carbonic acid

(H(H22COCO33) system) system

HLAHLA→→ H H-- + LA + LA--

HH++ + HCO + HCO33--→→ H H22COCO33

HH22COCO33→→HH22O + COO + CO22

McArdle’s Syndrome:McArdle’s Syndrome:

lack enzyme phosphorylaselack enzyme phosphorylase still demonstrate ventilatory or “anaerobic still demonstrate ventilatory or “anaerobic

threshold”threshold”

Healthy young men: normally fed Healthy young men: normally fed and glycogen-depletedand glycogen-depleted

after depletion: ventilatory threshold at lower after depletion: ventilatory threshold at lower power output and blood lactate threshold at power output and blood lactate threshold at a higher power outputa higher power output

dissociation of Tdissociation of Tventvent and T and Tlactlact in young men in young men

after endurance trainingafter endurance training

RecoveryRecovery

active: cool down or tapering, submaximal active: cool down or tapering, submaximal exerciseexercise

passive: no exercise, lie downpassive: no exercise, lie down

Optimal recovery from steady Optimal recovery from steady rate exerciserate exercise

if ex. <55-60% of max, little build up of HLAif ex. <55-60% of max, little build up of HLA recovery: resynthesis of high energy recovery: resynthesis of high energy

phosphates, replenish oxygen in blood, phosphates, replenish oxygen in blood, body fluids, myoglobin, increased ventilationbody fluids, myoglobin, increased ventilation

recovery is more rapid with passive recovery is more rapid with passive recovery, exercise elevate metabolism and recovery, exercise elevate metabolism and delay return to restingdelay return to resting

Optimal recovery from non-Optimal recovery from non-steady rate exercisesteady rate exercise

if exercise > 55-60% of max, HLA if exercise > 55-60% of max, HLA accumulationaccumulation

fatiguefatigue HLA removal from blood is accelerated by HLA removal from blood is accelerated by

active recoveryactive recovery 29-45% VO29-45% VO22 max is optimal for bike max is optimal for bike

exerciseexercise

55-60% is optimal for TM exercise55-60% is optimal for TM exercise difference is probably due to localized difference is probably due to localized

nature of bike exercise, lower HLA nature of bike exercise, lower HLA accumulationaccumulation

Active RecoveryActive Recovery

40 min 35% of VO40 min 35% of VO22 max max

40 min 65% of VO40 min 65% of VO22 max max

40 min combination: 7 min @ 65%, 33 min 40 min combination: 7 min @ 65%, 33 min @ 35%@ 35%

40 min passive40 min passive which is best? why?which is best? why?

active recovery:active recovery: increases blood flow to active musclesincreases blood flow to active muscles increases oxidation of LAincreases oxidation of LA brings it to heart and liver, which have brings it to heart and liver, which have

increased perfusionincreased perfusion

Intermittent ExerciseIntermittent Exercise

decrease the LA buildup, contribution from decrease the LA buildup, contribution from anaerobic metabolismanaerobic metabolism

can increase the capacity of aerobic system can increase the capacity of aerobic system to sustain exercise at a high rate of aerobic to sustain exercise at a high rate of aerobic energy transferenergy transfer

if exhaustion would ensue 3-5 minutes if if exhaustion would ensue 3-5 minutes if performed continuously, interval training performed continuously, interval training would benefitwould benefit

work to rest cycles, supramaximal work to rest cycles, supramaximal exercise to overload the desired energy exercise to overload the desired energy systemsystem

if exercise < 8 sec, intramuscular if exercise < 8 sec, intramuscular phosphates “worked”phosphates “worked”

this form of exercise has a rapid this form of exercise has a rapid recovery, why?recovery, why?

will discuss this more when discuss will discuss this more when discuss training aerobic and anaerobic energy training aerobic and anaerobic energy systems systems