Measuring and Evaluating Energy Expenditure

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Measuring and Evaluating Energy Expenditure

• McArdle, Katch, Katch
• Chapter 7

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Overview of Energy Transfer during Exercise

• Overlapping area represents generality.
• For each energy system, specificity exceeds
  generality.
• Effects of exercise training remain highly
  specific.

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Overview of Energy Transfer during Exercise

• At initiation of high- or low speed movements,
  intramuscular phosphagens provide immediate and
  nonaerobic energy.
• After first few seconds, glycolytic energy system
  provides greater proportion of total energy.
• Continuation, places greater demand on aerobic
  pathways.

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Measuring Evaluating Anaerobic Energy Systems

• Evaluating Immediate Energy Systems
• Measure changes in chemical substances used or
  produced
• Quantify amount of external work performed during
  short-duration, high-intensity activity.

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Evaluating Immediate Energy Systems

• Power F x D/time
• Muscular short term power by sprinting up flight
  of steps
• Jumping-power tests may not measure anaerobic
  power because too brief to evaluate ATP and PCr.

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Evaluating Immediate Energy Systems

• Other power tests last 6 to 8 seconds.
• Relationship among power tests not consistently
  strong because human performance is task specific.

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Evaluating Short-Term Energy System

• Level of blood lactate is most common indicator
  of short-term energy system.
• Glycogen depletion in specific muscles activated
  provides indication of contribution of glycolysis
  to exercise.
• Tests demanding work for up to 3 min. duration
  best estimate glycolytic power.

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Evaluating Short-Term Energy System

• Katch test peak power represents anaerobic power
  total work accomplished reflects anaerobic
  capacity.
• Wingate test provides peak power output and
  average power output.
• What is anaerobic fatigue?

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Factors Affecting Anaerobic Performance

• Specific anaerobic training
• Trained have more glycogen depletion than
  untrained
• Trained have higher levels of HLa
• Buffering capacity (alkaline reserve)
• Motivation

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Measuring Evaluating the Aerobic System

• Direct Calorimetry.
• Unit to measure heat is calorie. One calorie is
  amt. heat necessary to raise the temperature of
  one gram of water by 1o Celsius. Kilocalorie is
  generally used, 1 Kcal 1,000 calories.
• Process measuring animals metabolic rate via
  measurement of heat direct calorimetry.

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Direct Calorimetry

• Direct Calorimetry
• Theory when body uses energy to do work, heat is
  liberated.
• Foodstuff Oxygen ? ATP heat
• ?
• Cell work heat
• Therefore, measuring heat production
  (calorimetry) by animal gives a direct
  measurement of metabolic work.

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Measuring Evaluating the Aerobic System

• Technique places human in airtight chamber
  (calorimeter) which is insulated from environment
  and allowance is made for exchange O2 CO2. Body
  temperature raises temperature of water ?
  computer heat production

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Measuring Evaluating the Aerobic System

• Indirect Calorimetry
• Theory. Since direct relationship between O2
  consumed amt. heat produced by body,
  measurement of O2 consumption provides estimate
  of metabolic rate.
• Foodstuffs O2 ? Heat CO2 H2O
• (indirect) (direct)
• Measurement of oxygen consumption is indirect,
  since heat not measured directly.

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Indirect Calorimetry

• Closed circuit spirometry involves rebreathing
  same air.
• Open circuit spirometry involves breathing
  atmospheric air.

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Indirect Calorimetry

• Open circuit spirometry measures the volume and
  samples the air expired for percent of oxygen and
  carbon dioxide.

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Indirect Calorimetry

• Volume of oxygen consumed per minute is
  calculated as volume O2 inspired volume O2
  expired.
• Inspired VO2 ventilationI x .2093
• Expired VO2 ventilationE x ( O2 expired)

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Indirect Calorimetry

• Volume of carbon dioxide consumed per minute is
  calculated as volume CO2 expired volume CO2
  inspired.
• VCO2 ventilationI x ( CO2 expired)
• VO2 ventilationE x ( CO2 inspired)

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Caloric Transformation for Oxygen
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Caloric Transformation for Oxygen

• Physiological fuel value of _at_ nutrient is amount
  of usable energy per gram nutrient.
• Heat of combustion
• digestibility
• Urinary nitrogen loss
• Caloric value for oxygen varies slightly (w/i 2
  4 ) with variation in nutrient mixture.

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Respiratory Quotient

• Respiratory quotient (RQ) is ratio of volume of
  carbon dioxide produced to volume of oxygen
  consumed.
• RQ for Carbohydrate is 1.0.
• Glucose C6H12O6 6 O2 ? 6 CO2 6 H2O
• RQ 6 CO2/ 6 O2 1

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Respiratory Quotient

• RQ for fat is .70
• C16H32O2 23 O2 ? 16CO2 16 H2O
• RQ 16CO2 / 23 O2 .7
• RQ for protein is .82
• Protein must first be deaminated in liver.
• Resulting keto acid fragments oxidized
  requiring O2 gt CO2

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Respiratory Quotient

• RQ for mixed diet is .82.
• Non-protein RQ is between 0.7 and 1.0.
• Thermal equivalents of oxygen for different
  non-protein mixtures.

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Respiratory Exchange Ratio

• Respiratory Exchange Ratio is ratio of carbon
  dioxide exhaled to oxygen taken up by the body.
• RER ? RQ during hyperventilation and exhaustive
  exercise. Non-metabolic CO2.
• Exhaustive exercise presents RER gt 1.00.
• HLa NaHCO3 ? NaLa H2CO3 ? CO2 H20
• Lactate Buffering by Sodium Bicarbonate.

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Measuring Maximal Oxygen Consumption

• The highest maximal oxygen uptakes generally
  recorded for cross-country skiers, runners,
  swimmers, and cyclists.
• Lance Armstrong VO2 max 83.3 ml/kg/min

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Measuring Maximal Oxygen Consumption

• Criteria for true max VO2 is leveling off or
  peaking in oxygen uptake.
• Other criteria
• Oxygen uptake fails to increase by some value
• Maximum lactic acid of 70-80 mg/100 mL
• Maximum predicted HR or R gt 1.0

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Measuring Maximal Oxygen Consumption

• Tests of Aerobic Power
• Two general criteria
• Independent of muscle strength, speed, body size,
  skill
• Consists of graded exercise to point of
  exhaustion (without muscular fatigue)

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Measuring Maximal Oxygen Consumption

• Continuous versus Discontinuous
• Small differences between continuous
  discontinuous on bicycle, but lower than
  treadmill tests.

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Measuring Maximal Oxygen Consumption

• Commonly used protocols.
• Vary
• Exercise duration
• Treadmill speed
• Treadmill grade

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Measuring Maximal Oxygen Consumption

• Factors that affect Maximal Oxygen Uptake
• Mode
• Heredity
• State of training
• Gender
• Body composition
• Age

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Predicting VO2 Max

• Walking Running Tests use age, gender, time for
  test, HR at end of test
• Predictions based on HR linearity.
• Similar maximum HRs for healthy people.

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Illustration References

• McArdle, William D., Frank I. Katch, and Victor
  L. Katch. 2000. Essentials of Exercise
  Physiology 2nd ed. Image Collection. Lippincott
  Williams Wilkins.
• Plowman, Sharon A. and Denise L. Smith. 1998.
  Digital Image Archive for Exercise Physiology.
  Allyn Bacon.
• Axen, Kenneth and Kathleen Axen. 2001.
  Illustrated Principles of Exercise Physiology.
  Prentice Hall.