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• Evaluation provides info about absolute and relative intensity of exercise bout (fig 10.1a)
– absolute VO2 (L/min or ml/Kg/min)– % of VO2 max– % of HR max– multiples of Metabolic Rate (MET’s)
• 1kcal/Kg/hour at rest
• determination of metabolic response allows estimation of – Total energy cost– Nutritional requirements– Efficiency calculations– Estimation of workload indicates
metabolic system utilization, and the potential for fatigue
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Substrate Utilization• Brooks p 133• Power output is the most important
– post absorptive and resting• lipid used predominantly
– with increasing intensity• fuel mix switches from lipid to CHO
• Fig 7-12• training - displaces absolute intensity
at which crossover occurs – epinephrine suppression– inc lactate clearance– inc mitochondria – prolong onset of glycogen breakdown,
depletion and fatigue
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Fuel Utilization• Fig 7-11• Glucose - fatty acid cycle• FFA breakdown inhibits glycolysis• PDH is inhibited by Acetyl-CoA
from Beta oxidation• PFK is inhibited by inc citrate from
Beta oxidation and ATP– in highly trained and glycogen depleted
this is accentuated– Fig 7-10 - higher FFA utilization with
higher mitochondrial enzyme activity following training
• Hexokinase is inhibited by its product G6P, which builds up if glycolysis is not active.
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Recovery from Exercise• Ch. 3 - Foss• process of recovery from exercise
involves transition from catabolic to anabolic state– breakdown of glycogen and fats to
replenishment of stores– breakdown of protein to protein
synthesis for muscle growth and repair
• Our discussion of recovery will include;– oxygen consumption post exercise– Replenishment of energy stores– Lactate metabolism(energy or glycogen)
– Replenishment of oxygen stores– intensity and activity specific recovery– guidelines for recovery
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Recovery Oxygen• Recovery O2 - Net amount of oxygen
consumed during recovery from exercise– excess above rest in Litres of O2
• Fast and Slow components– Based on slope of O2 curve– first 2-3 min of recovery - O2 consumption
declines fast– then declines slowly to resting
• Fig 3.1• Fast Component - first 2-3 minutes
– restore myoglobin and blood oxygen– energy cost of elevated ventilation– energy cost of elevate heart activity– replenishment of phosphagen
• volume of O2 for fast component = area under curve– related to intensity not duration
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Recovery Oxygen
• Slow Component– elevated body temperature
• Q10 effect - inc metabolic activity
– cost of ventilation and heart activity– ion redistribution Na+/K+ pump– glycogen re-synthesis– effect of catecholamines and thyroid hormone– oxidation of lactate serves as fuel for many of
these processes
• duration and intensity do not modify slow component until threshold of combined duration and intensity– After 20 min and 80% – We observe a 5 fold increase in the volume of
the slow component
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Energy Stores• Both phosphagens (ATP, CP) and glycogen
are depleted with exercise
• ATP/CP - recover in fast component– measured by sterile biopsy, MRS
– rate of PC recovery indicative of net oxidative ATP synthesis (VO2)
– study of ATP production• 20-25 mmol/L/min glycogen and all fuels
• during exercise– CP can drop to 20%, ATP to 70 %
– CP lowest at fatigue, rises immediately with recovery
• Fig 3.2 - very rapid recovery of CP– 30 sec 70%, 3-5 min 100% recovery
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Phosphagen Recovery(cont.)• Fig 3.3
– occlusion of blood flow - no phosphogen recovery
– ** requires aerobic metabolism– estimate 1.5 L of oxygen for ATP-PC recovery
• Energetics of Recovery• Fig 3.4
– breakdown carbs, fats some lactate– produce ATP which reforms CP– high degree of correlation between phosphagen
depletion and volume of fast component oxygen
• Fig. 3.5– Strong correlation between phosphagen
depletion and volume of the fast component of recovery oxygen - sea level and altitude
• anaerobic power in an athlete related to phosphagen potential - Wingate test
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Glycogen Re-synthesis• Requires 1-2 days and depends on
– type of exercise and amount of dietary carbohydrates consumed
• Two types of exercise investigated– continuous endurance (low intensity)– intermittent exhaustive (high intensity)
• Continuous - (low- moderate intensity)
• Fig 3.6 - diet effect– minor recovery in 1-2 hours, does not
continue with fasting– complete re-synthesis requires high
carbohydrate diet ~ 2 days
– Recovery does not occur without high carbohydrate diet
– depletion of glycogen related to fatigue– Fig 3.7 - heavy training