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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