Understanding Energy Expenditure: Measurement and Evaluation

1. Measuring and Evaluating Energy Expenditure McArdle, Katch, & Katch Chapter 7

2. Overview of Energy Transfer during Exercise • Overlapping area represents generality. • For each energy system, specificity exceeds generality. • Effects of exercise training remain highly specific.

3. 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.

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

5. Evaluating Immediate Energy System • 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.

6. Evaluating Immediate Energy Systems • Other power tests last 6 to 8 seconds. • Low interrelationship among power tests suggests high degree of task specificity. The best sprint runner may not be the best repetitive volleyball leaper.

7. Evaluating Short-Term Glycolytic Energy System • Blood lactate level is most common indicator of short-term energy system (7.3). • Glycogen depletion in specific muscles activated provides indication of contribution of glycolysis to exercise (figure 7.4). • Tests demanding maximual work for up to 3 min. best estimate glycolytic power.

8. Evaluating Short-Term Energy System • In Katch cycle test peak power represents anaerobic power & total work accomplished reflects anaerobic capacity. • Wingate test provides peak power output,average power output, and anaerobic fatigue. • What is anaerobic fatigue?

9. 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

10. 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 animal’s metabolic rate via measurement of heat: direct calorimetry.

11. 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.

12. 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

13. 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.

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

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

16. 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)

17. Indirect Calorimetry • Volume of carbon dioxide consumed per minute is calculated as volume CO2 expired –volume CO2 inspired. • Expired VCO2 = ventilationE x (% CO2 expired) • Inspired VCO2 = ventilationI x (.03%)

18. Caloric Transformation for Oxygen • Approximately 4.82 kcals release when blend of CHO, pro, fat burns in 1 L O2. • Physiological fuel value of @ 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.

19. Caloric Transformation for Oxygen

20. 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

21. Respiratory Quotient • RQ for fat is .70 C16H32O2 + 23 O2  16CO2 + 16 H2O RQ = 16 CO2 / 23 O2 = .7 • RQ for protein is .82 Protein must first be deaminated in liver. Resulting “keto acid” fragments oxidized requiring O2 > CO2

22. Respiratory Quotient RQ for mixed diet is .82 from 40% CHO & 60% fat. • Non-protein RQ is between 0.7 and 1.0. • Thermal equivalents of oxygen for different non-protein mixtures.

23. Respiratory Exchange Ratio Respiratory Exchange Ratio is ratio of carbon dioxide exhaled to oxygen consumed when CO2 and O2 exchange doesn’t reflect food oxidation. RER ≠ RQ during hyperventilation and exhaustive exercise. Non-metabolic CO2. • Exhaustive exercise presents RER > 1.00. HLa + NaHCO3 NaLa + H2CO3  CO2+ H20 Lactate Buffering by Sodium Bicarbonate.

24. 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

25. 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 > 1.0

26. 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)

27. Measuring Maximal Oxygen Consumption • Continuous versus Discontinuous • Small differences between continuous & discontinuous on bicycle, but lower than treadmill tests.

28. Measuring Maximal Oxygen Consumption • Commonly used protocols. • Vary • Exercise duration • Treadmill speed • Treadmill grade

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

30. Predicting VO2 Max • Walking & Running Tests use age, gender, time for test, HR at end of test • Predictions based on HR: VO2 linearity. • Similar maximum HRs for healthy people.

31. 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.