AIS Chap 5 Anaerobic capacity

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

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

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

The Oxygen Deficit

Differences in VO2 Between Trained and Untrained Subjects

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

Assumption and criteria for MAOD as good estimation for anaerobic capacity 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)

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

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

Maximal accumulated oxygen deficit (MAOD) Medbo JI, 1988

Accumulated oxygen deficit vs duration of supramaximal exercise Medbo JI, 1988

Relative accumulated oxygen deficit Medbo JI, 1988

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

Oxygen Deficit and Debt During Light-Moderate and Heavy Exercise

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