Measuring and Evaluating Energy Expenditure Mc Ardle Katch
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Measuring and Evaluating Energy Expenditure Mc. Ardle, Katch, & Katch Chapter 7
Overview of Energy Transfer during Exercise u Overlapping area represents generality. u For each energy system, specificity exceeds generality. u Effects of exercise training remain highly specific.
Overview of Energy Transfer during Exercise u u u At initiation of high- or lowspeed 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.
Measuring & Evaluating Anaerobic Energy Systems Evaluation of Immediate Energy System u Measure changes in chemical substances used or produced u Quantify amount of external work performed during short-duration, highintensity activity.
Evaluating Immediate Energy System u Power = F x D/time u Muscular short term power by sprinting up flight of steps u Jumping-power tests may not measure anaerobic power because too brief to evaluate ATP and PCr.
Evaluating Immediate Energy Systems u Other power tests last 6 to 8 seconds. u Low interrelationship among power tests suggests high degree of task specificity. The best sprint runner may not be the best repetitive volleyball leaper.
Evaluating Short-Term Glycolytic Energy System u Blood lactate level is most common indicator of short-term energy system (7. 3). u Glycogen depletion in specific muscles activated provides indication of contribution of glycolysis to exercise (figure 7. 4). u Tests demanding maximual work for up to 3 min. best estimate glycolytic power.
Evaluating Short-Term Energy System u In Katch cycle test peak power represents anaerobic power & total work accomplished reflects anaerobic capacity. u Wingate test provides peak power output, average power output, and anaerobic fatigue. u What is anaerobic fatigue?
Factors Affecting Anaerobic Performance u Specific anaerobic training u Trained have more glycogen depletion than untrained u Trained have higher levels of HLa u Buffering capacity (alkaline reserve) u Motivation
Measuring & Evaluating the Aerobic System Direct Calorimetry. u Unit to measure heat is calorie. One calorie is amt. heat necessary to raise the temperature of one gram of water by 1 o Celsius. Kilocalorie is generally used, 1 Kcal = 1, 000 calories. u Process measuring animal’s metabolic rate via measurement of heat: direct calorimetry.
Direct Calorimetry u 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.
Measuring & Evaluating the Aerobic System Technique places human in airtight chamber (calorimeter) which is insulated from environment and allowance is made for exchange O 2 & CO 2. Body temperature raises temperature of water computer heat production
Measuring & Evaluating the Aerobic System Indirect Calorimetry u Theory. Since direct relationship between O 2 consumed & amt. heat produced by body, measurement of O 2 consumption provides estimate of metabolic rate. Foodstuffs + O 2 Heat + CO 2 + H 2 O (indirect) (direct) u Measurement of oxygen consumption is indirect, since heat not measured directly.
Indirect Calorimetry u Closed circuit spirometry involves rebreathing same air. u Open circuit spirometry involves breathing atmospheric air.
Indirect Calorimetry Open circuit spirometry measures the volume and samples the air expired for percent of oxygen and carbon dioxide.
Indirect Calorimetry u u u Volume of oxygen consumed per minute is calculated as volume O 2 inspired –volume O 2 expired. Inspired VO 2 = ventilation. I x. 2093 Expired VO 2 = ventilation. E x (% O 2 expired)
Indirect Calorimetry u Volume of carbon dioxide consumed per minute is calculated as volume CO 2 expired – volume CO 2 inspired. u Expired VCO 2 = ventilation. E x (% CO 2 expired) u Inspired VCO 2 = ventilation. I x (. 03%)
Caloric Transformation for Oxygen u Approximately 4. 82 kcals release when blend of CHO, pro, fat burns in 1 L O 2. u Physiological fuel value of @ nutrient is amount of usable energy per gram nutrient. u Heat of combustion u % digestibility u Urinary nitrogen loss u Caloric value for oxygen varies slightly (w/i 2 – 4 %) with variation in nutrient mixture.
Caloric Transformation for Oxygen Food CHO Energy oxygen carbon RQ calmeter physiologic (kcal/L) dioxide 4. 1 4. 02 5. 05 1 Pro 5. 65 4. 3 4. 46 5. 44 . 82 Fat 9. 45 8. 98 4. 68 6. 63 . 71 4. 82 5. 89 . 82 Mixed
Respiratory Quotient u Respiratory quotient (RQ) is ratio of volume of carbon dioxide produced to volume of oxygen consumed. u RQ for Carbohydrate is 1. 0. Glucose C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O RQ = 6 CO 2/ 6 O 2 = 1
Respiratory Quotient u RQ for fat is. 70 C 16 H 32 O 2 + 23 O 2 16 CO 2 + 16 H 2 O RQ = 16 CO 2 / 23 O 2 =. 7 u RQ for protein is. 82 Protein must first be deaminated in liver. Resulting “keto acid” fragments oxidized requiring O 2 > CO 2
Respiratory Quotient RQ for mixed diet is. 82 from 40% CHO & 60% fat. u Non-protein RQ is between 0. 7 and 1. 0. u Thermal equivalents of oxygen for different non-protein mixtures.
Respiratory Exchange Ratio is ratio of carbon dioxide exhaled to oxygen consumed when CO 2 and O 2 exchange doesn’t reflect food oxidation. RER ≠ RQ during hyperventilation and exhaustive exercise. Non-metabolic CO 2. u Exhaustive exercise presents RER > 1. 00. HLa + Na. HCO 3 Na. La + H 2 CO 3 CO 2 + H 20 Lactate Buffering by Sodium Bicarbonate.
Measuring Maximal Oxygen Consumption u The highest maximal oxygen uptakes generally recorded for cross-country skiers, runners, swimmers, and cyclists. u Lance Armstrong VO 2 max = 83. 3 ml/kg/min
Measuring Maximal Oxygen Consumption Criteria for true max VO 2 is leveling off or peaking in oxygen uptake. u Other criteria: u u Oxygen uptake fails to increase by some value u Maximum lactic acid of 70 -80 mg/100 m. L u Maximum predicted HR or R > 1. 0
Measuring Maximal Oxygen Consumption Tests of Aerobic Power u Two general criteria: u Independent of muscle strength, speed, body size, skill u Consists of graded exercise to point of exhaustion (without muscular fatigue)
Measuring Maximal Oxygen Consumption u Continuous u Small versus Discontinuous differences between continuous & discontinuous on bicycle, but lower than treadmill tests.
Measuring Maximal Oxygen Consumption u Commonly used protocols. u Vary u Exercise duration u Treadmill speed u Treadmill grade
Measuring Maximal Oxygen Consumption u Factors that affect Maximal Oxygen Uptake u Mode u Heredity u State of training u Gender u Body composition u Age
Predicting VO 2 Max u Walking & Running Tests use age, gender, time for test, HR at end of test u Predictions based on HR: VO 2 linearity. u Similar maximum HRs for healthy people.
Illustration References u Mc. Ardle, William D. , Frank I. Katch, and Victor L. Katch. 2000. Essentials of Exercise Physiology 2 nd ed. Image Collection. Lippincott Williams & Wilkins. u Plowman, Sharon A. and Denise L. Smith. 1998. Digital Image Archive for Exercise Physiology. Allyn & Bacon. u Axen, Kenneth and Kathleen Axen. 2001. Illustrated Principles of Exercise Physiology. Prentice Hall.
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