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Chapter 6 Measurement of Work, Power, and Energy Expenditure

Chapter 6 Measurement of Work, Power, and Energy Expenditure. EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6 th edition Scott K. Powers & Edward T. Howley. Objectives. Define the terms work, power, energy, and net efficiency

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Chapter 6 Measurement of Work, Power, and Energy Expenditure

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  1. Chapter 6Measurement of Work, Power, and Energy Expenditure EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Howley

  2. Objectives • Define the terms work, power, energy, and net efficiency • Give a brief explanation of the procedure used to calculate work performed during cycle ergometer exercise and treadmill exercise • Describe the concept behind the measurement of energy expenditure using direct and indirect calorimetry

  3. Objectives • Discuss the procedure used to estimate energy expenditure during horizontal treadmill walking and running • Define the following terms: kilogram-meter, relative VO2, MET, and open-circuit spirometry

  4. Units of Measure • English system used in United States • Metric system is the standard system of measurement for scientists • Used to express… • Mass – _________ • Length – _________ • Volume – _________ • System International units or SI units • Standardized terms for measurement of: • Energy • Force • Work • Power

  5. Work is the product of force and distance Work = ___________ x ___________ Lifting a 5 kg weight up a distance of 2 m Work = force x distance Work = 5 kp x 2 m Work = 10 kpm Kg – measure of mass, not force Kp = force acting on a mass of 1 ____ at normal gravity Work

  6. Power is how much work is done per unit of time Power = ________ / __________ Performing 2,000 kpm of work in 1min Power = work/time Power = 2,000 kpm/1min Power = 2000 kpm•min-1 SI Units = 1 Watt (W) = 6.12 kpm•min-1 Power = __________ W Power

  7. Measurement of Work and PowerBench Step Work = Work = body weight (kg) x distance (m) = 70 kp x 150 m = 10,500 kpm Power = work  minutes = 10,500 kpm/10 min = 1,050 kpm/min or 171.6 W

  8. Measurement of Work and PowerCycle Ergometer Work = Work = force (kg) x distance (m) = 1.5 kp x (6m/rev x 600 rev) = 5,400 kpm • Power = work  minutes = 5,400 kpm/10 min = 540 kpm/min or 88.2 W

  9. Measurement of Work and PowerTreadmill • Calculation of work performed while a subject runs or walks on a treadmill is not generally possible when the treadmill is ___________________. • Although running horizontal on a treadmill requires energy • Work performed during horizontal walking or running is complicated • Quantifiable work is being performed when walking or running _____________

  10. Measurement of Work and PowerTreadmill • Incline of the treadmill is expressed in percent grade • Percent grade is the amount of vertical rise per 100 units of belt travel Vertical displacement = ________________ Treadmill speed = 200m/min Percent Grade = 7.5% or 0.075 Exercise time = 10 mins Total vertical distance traveled =

  11. Measurement of Work and PowerTreadmill Work = _____________________________ = 70 kp x 150 m = 10,500 kpm Power = work  minutes = 10,500 kpm/10min = 1,050 kpm/min or Watts

  12. Cell work Foodstuff + O2 ATP + Heat Heat Measurement of Energy Expenditure • _____________________ • Measurement of heat production as an indication of metabolic rate • _____________________ • Measurement of oxygen consumption as an estimate of resting metabolic rate Foodstuff + O2 Heat + CO2 + H2O

  13. Open-Circuit Spirometry Fig 6.4

  14. Estimation of Energy Expenditure • Expression of energy cost in METs • 1 MET = _______________ • 1 MET = _______________ • Absolute O2 requirement of activity at 10 METS >>> example – p. 115

  15. x 100 % net efficiency = Calculation of Exercise Efficiency • Net efficiency • Net efficiency of cycle ergometry • 15-27%

  16. Factors That Influence Exercise Efficiency • Exercise work rate • Efficiency decreases as work rate increases • Speed of movement • There is an optimum speed of movement, and any deviation reduces ______________ • Fiber composition of muscles • Higher efficiency in muscles with greater percentage of _________________

  17. Relationship Between Energy Expenditure and Work Rate Fig 6.9

  18. Net Efficiency During Arm Crank Ergometery Fig 6.8

  19. Effect of Speed of Movement of Net Efficiency Fig 6.10

  20. Running Economy • Running Economy • Oxygen cost of running at given speed • Lower VO2 (ml•kg-1•min-1) indicates better running economy • Gender difference in running economy • No difference at slow speeds • At “race pace” speeds, males may be more economical than females

  21. Comparison of Running Economy Between Males and Females Fig 6.11

  22. Chapter 6Measurement of Work, Power, and Energy Expenditure

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