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AIS Chap 5Anaerobic capacity

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Anaerobic power and anaerobic capacity

• Anaerobic power 無氧動力 : Peak rate of ATP produced via anaerobic metabolism, difficult to measure directly– Usually estimated from peak power output during all-out

sprint-type exercise• Anaerobic capacity 無氧能力 : Maximal amount of

ATP that can be generated through anaerobic metabolism, during short-duration maximal ex– Important for 400-1500 m running, 200-400 m freestyle

swimming, 1-4 km track cycling, 2000 m rowing, 500-1000 m kayaking, team sports

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Measure anaerobic ATP production

• Muscle biopsy 肌肉穿刺 : Changes in muscle metabolites

• Blood lactate after supramaximal exercise • Oxygen debt 氧債 after supramaximal exercise • Total work or mean power output during short-

duration maximal exercise–Wingate test (30 s all-our cycling), 9-40% ATP

produced aerobically– Tests < 60 s inadequate to exhaust anaerobic system

• Accumulated oxygen deficit

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Rest-to-Exercise Transitions

• Oxygen uptake increases rapidly– Reaches steady state within 1-4 minutes

• Oxygen deficit– Lag in oxygen uptake at the beginning of

exercise– Suggests anaerobic pathways contribute to most

ATP production• After steady state is reached, ATP

requirement is met through aerobic ATP production

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The Oxygen Deficit

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Differences in VO2 Between Trained and Untrained Subjects

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accumulated oxygen deficit• At submaximal exercise: O2 consumption meets

energy demand at steady state, aerobic metabolism– Linear VO2-power output relationship

• Supramaximal exercise: required ATP from aerobic + anaerobic metabolism– Exercise performed at a power output higher than that

achieved at VO2peak– <60 sec sprint, or 2-4 min at constant power output– Accumulated oxygen deficit = calculated accumulated

oxygen demand – measured accumulated oxygen demand• MAOD: maximally accumulated oxygen deficit– Valid and reliable measurement for anaerobic capacity

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Assumption and criteria for MAOD as good estimation for anaerobic capacity

• Assumption:– Mechanical efficiency identical in supra- and submaximal

exercise– the rate of total energy release (i.e. O2 demand) increases

linearly with the exercise intensity– O2 demand is constant during this type of supramaximal

exercise• Leveling off with exercise duration– Increased with duration of exhaustive exercise until level

off• Independent of maximal oxygen uptake (VO2max)

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Procedures

• VO2 – power output relationship– Originally 10 stages at 10 min per stage–Modified to fewer stages at 40-70% VO2max with 4

min per stage• Duration of performance test– Long enough to allow max anaerobic energy release– Short enough to minimize aerobic energy production– Constant power output 115-130% peak VO2– Or ‘all-out’ for a specific duration or distance

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Oxygen stores of body

• In transition from rest to exercise, mouth VO2 underestimate tissue VO2– O2 bind to hemoglobin and myoglobin– O2 dissolved in body fluids– O2 in lungs

• Estimated 9% oxygen deficit• Should be subtracted from absolute MAOD

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Maximal accumulated oxygen deficit (MAOD)

Medbo JI, 1988

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Accumulated oxygen deficit vs duration of supramaximal exercise

Medbo JI, 1988

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Relative accumulated oxygen deficit

Medbo JI, 1988

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MAOD range

• 38 ml/kg in middle distance trained athletes, to 100 ml/kg in sprint trained athletes– 60 kg: 2.3 L O2eq – 6 L O2eq

• MAOD unaffected by inspired O2 concentration– Independent of aerobic metabolism

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Oxygen Deficit and Debt During Light-Moderate and Heavy Exercise

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Recovery From Exercise: Metabolic Responses

• Oxygen debt– Elevated VO2 for several minutes immediately following

exercise– Excess post-exercise oxygen consumption (EPOC)

• “Fast” portion of O2 debt– Resynthesis of stored PC– Replacing muscle and blood O2 stores

• “Slow” portion of O2 debt– Elevated body temperature and catecholamines– Conversion of lactic acid to glucose (gluconeogenesis)醣質新生