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ACSM Exercise Specialist Workshop

ACSM Exercise Specialist Workshop. Metabolic Calculations Tutorial. Purpose of Metabolic Calculations. Under steady-state conditions, VO 2 provides a measure of the energy cost of exercise

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ACSM Exercise Specialist Workshop

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  1. ACSM Exercise Specialist Workshop Metabolic Calculations Tutorial

  2. Purpose of Metabolic Calculations • Under steady-state conditions, VO2 provides a measure of the energy cost of exercise • The rate of O2 uptake at maximal exercise indicates the capacity for O2 transport and utilization • Peak VO2 serves as the gold standard criterion measure of cardiorespiratory fitness • At steady state, and in combination with CO2 output, VO2 can provide information about type of fuel use during exercise • Determine work rates to be used in the development of exercise prescription

  3. Expression of VO2 • Absolute- Liters per minute (Lmin-1) • Used to convert consumption to a rate of energy expenditure • Relative- mL per kg body weight per min (mLkg-1min-1) • Used to compare VO2 among varying body sizes • Gross oxygen consumption- Total consumption rate under any circumstances, either in absolute or relative; describes rest plus exercise • Net oxygen consumption- Consumption rate above resting oxygen uptake (approx. 3.5 mLkg-1min-1); describes exercise

  4. RER-Respiratory Exchange Ratio Ventilatory measurement Reflects gas exchange between lungs and pulmonary blood Exceeds 1.0 during heavy exercise due to buffering of lactic acid which produces CO2 RQ-Respiratory Quotient Cellular Respiration and substrate utilization 0.7 = Fat 1.0 = Carbohydrate 0.8 = Protein Equivalent to RER only under resting or steady-state conditions Can never exceed 1.0 RQ is used to estimate energy expenditure, however, when RQ is not available, assume 5 kcal L-1 RER and RQ

  5. Estimation of Energy Expenditure • When VO2 cannot be measured directly, estimations can be made during steady-state exercise (will overestimate VO2 if not at steady-state) • Equations are based on relating mechanical work rate to metabolic equivalents • Equations are appropriate for general clinical and lab use

  6. Estimation of Energy Expenditure • Equations can be used for: • Estimating or predicting energy expenditure • Designing an exercise prescription to determine the exercise intensity associated with a desired level of energy expenditure

  7. Cautionary Notes • The inter-subject variability for VO2 may be as high as 7% • Appropriate for steady-state submaximal aerobic exercise • Any variable that changes the metabolic efficiency results in loss of accuracy (e.g., orthopedic limitations, holding handrail on treadmill, etc.) • Assumes that a metabolic cart or gas analyzers and flow indicators are calibrated and used properly • Despite these caveats, metabolic equations provide a valuable tool for exercise professionals

  8. 1L= 1000 mL 1kg= 2.2 lbs 1mph= 26.8 mmin-1 1lb of fat= 3500kcal 1 MET=3.5 mLkg-1min-1 1 W= 6 kgmmin-1 1L O2min-1= 5 kcalmin-1 1 in= 0.0254m=2.54 cm Conversion Factors MEMORIZE MEMORIZE MEMORIZE

  9. Located in Appendix D of GETP6

  10. Conversion Flowchart METS lb fat loss/gain  3.5 X 3.5 3500 X 3500 mLkg-1min-1 Total kcal X Tot min  Tot min  BW X BW X 1000 X 5 mLmin-1 L min-1 Kcalmin-1  1000  5

  11. Walking (1.93.75 mph) • VO2= (0.1S) + (1.8 S G) + 3.5 Horizontal Vertical Rest S= speed in mmin-1(convert if needed) G= grade in decimal form (i.e., 5% is 0.05); if 0% grade, then vertical=0 R= resting component NOTE: VO2 is reported as mLkg-1min-1

  12. Running (>5.0mph) • VO2= (0.2 S) + (0.9 S G) + 3.5 Horizontal Vertical Rest • All variables are the same as for walking • NOTE: VO2 is reported as mLkg-1min-1

  13. Leg Ergometry • VO2= (10.8 W/M) + 7 • M= mass (weight) of subject in kg • W= Work rate in watts, • convert when necessary • 1 W= 6 kgmmin-1 • kgmmin-1=R D f • R= resistance in kg • D= distance of the fly wheel • 6m for Monark • 3m for Tunturi • f= frequency in rpm • NOTE: VO2 is reported as mLkg-1min-1

  14. Arm Ergometry • VO2= 18(W/M) + 3.5 • Find work rate the same as leg ergometry • Major difference: • D=2.4 for Monark • NOTE: VO2 is reported as mLkg-1min-1

  15. Stepping Ergometry • VO2= (0.2 f) + (1.33 1.8 f h) + 3.5 • f=stepping rate • h=height of step in m • NOTE: VO2 is reported as mLkg-1min-1

  16. Question #1 • VO2= (0.1x85.76)+(1.8x85.76x.06)+3.5 • VO2= 8.576 + 9.26 + 3.5 • VO2= 21.34 mLkg-1min-1 • 21.34/3.5 = 6.1 METs

  17. Question #2 • VO2 = (0.2x241.2)+(0.9x241.2x.01)+3.5 • VO2 = 48.24 + 2.17 + 3.5 • VO2 = 53.9 mLkg-1min-1 • VO2 = 53.9 mLkg-1min-1 x 68.0 kg=3665.2 mLmin-1 • VO2(Lmin-1) =3665.2 mLmin-1/1000 mLL-1 = 3.67 Lmin-1 • Kcalsmin-1 = 3.67 Lmin-1x5 kcals L-1 =18.4 Kcalsmin-1 • Kcals in 40 minutes = 18.4 Kcalsmin-1 x 40min.= 736 kcals expended in 40 minutes

  18. Question #3 • 50 kg man walking at 75% VO2 reserve. Max VO2 = 2.4 Lmin-1. What speed at a grade of 12%. • 2.4 Lmin-1 = 2400 mLmin-1 • 2400 mLmin-1 ÷ 50 kg = 48 mLkg-1min-1 • 48 mLkg-1min-1 x 0.75 = 36 mLkg-1min-1 • 36 = (0.1)(x) + (1.8)(x)(0.12) + 3.5 • 36 = 0.1x + 0.21x + 3.5 • 32.5 = 0.31x • x = 104.8 mmin-1/26.8 mmin-1 = 3.9 mph

  19. Question #4 • VO2 = (0.2xS)+(0.9xSxG)+3.5 • 45.0 mLkg-1min-1 = 0.2x87.6)+(0.9x187.6xG)+3.5 • 45.0 mLkg-1min-1 = 37.52 + 168.8(G) + 3.5 • 3.98 = 168.8 (G) • 0.024 = G or 2.4%

  20. Question #5 • VO2 = (18 x W/M) + 3.5 • where W = 0.5kg x 2.4m x 50rpm • w=60 kgmmin-1 or 10 watts • VO2 mLkg-1min-1 = (18 x 10)/50 + 3.5 • VO2 = 180/50 + 3.5 • VO2 = 3.6 + 3.5 • VO2 = 7.1 mLkg-1min-1

  21. Question #6 • 176 lbs/2.2 = 80 kg • Warm Up • 2.5 x 3.5 = 8.75 mLkg-1min-1 • 8.75 mLkg-1min-1x80 kg=700 mLmin-1 • 700 mLmin-1 /1000 mLL-1 =0.7 Lmin-1 • 0.7 Lmin-1 x 5 kcalsL-1 = 3.5 kcalsmin-1 x 5 min. = 17.5 kcals in 5 min.

  22. Question #6... continued • Exercise • 4.5 METs = 15.75 mLkg-1min-1 • 15.75mLkg-1min-1 x 80kg = 1260 mLmin-1 = 1.26 Lmin-1 • 1.26 Lmin-1 x 20 min =25.2 L x 5 kcal L-1 = 126 kcals in 20 min. • 4 METs = 14 mLkg-1min-1 • 14 mLkg-1min-1 x 80 kg = 1120 mLmin-1 = 1.12 Lmin-1 • 1.12 Lmin-1 x 15 min = 16.8 L x 5 kcal L-1 = 84 kcals

  23. Question # 6…continued • Cool Down • 2 METs = 7 mLkg-1min-1/80kg =560 mLmin-1 • 560 mLmin-1/1000 mLL-1 = 0.56 Lmin-1 • 0.56 Lmin-1 x 5 min = 2.8 L • 2.8 L x 5 = 14 kcals • 17.5 + 126 + 84 + 14= 241.5 Kcals

  24. Question #7 • 140 lbs = 63.6 kg • TM @ 3.2/0% • VO2 = 8.576+3.5=12.08 mLkg-1min-1 • 12.08 x 63.6 = 768.29 mLmin-1 • 768.29/1000 = 0.768 Lmin-1 • 0.768 x 10 = 7.7 l = 38.5 kcals • TM @ 3.4/2% = 50.5 kcals • TM @ 3.0/5% = 59.5 kcals • Total Kcals = 148.5 • 148.5 x 3 = 445.5/week • 3500 x 15 = 52,500 kcals • 52, 500 kcals/445.5 = 118 weeks @ 3 days/week

  25. Question # 8 • MET level of person with VO2 of 55 mLkg-1min-1? 55 mLkg-1min-1 ÷ 3.5 mLkg-1min-1 per MET = 15.7 METs

  26. Question # 9 • 60 kg women with a VO2 of 2400 mLmin-1. What is her MET level? • 2400 mLmin-1 ÷ 60kg = 40 mLkg-1min-1 • 40 mLkg-1min-1 ÷ 3.5 mLkg-1min-1 per MET = 11.4 METS

  27. Question #10 • 70 kg person using Stepper @ 18 stepsmin-1, 25 cm step • VO2 = (0.2 x f)+(1.33 x 1.8 x H x F) +3.5 • VO2 = (0.2 x 18) + (1.33x1.8x0.25x18) • VO2 = 3.6 + 10.8 • VO2 = 14.4 mLkg-1min-1 or 4.1 METs

  28. Question 10…continued • 70 kg person on Monark @ 750kgmmin-1 • 750 kgmmin-1 / 6 kgmmin-1 per watt= 125 watts • VO2 = (10.8x125)/70 + 7 • VO2 = 18.9 + 7 = 25.9 mLkg-1min-1 or 7.5 METs • (NOTE: may get 7.4 METS if use 6.12 kgmmin-1 as 1 watt)

  29. Question #10…continued • 70 kg person on Monark arm ergometer @ 350 kgmmin-1. • 350 kgmmin-1 = 58.3 watts • VO2 = (18x58.3)/70 + 3.5 • VO2 = 14.99 + 3.5 • VO2 = 18.49 or 5.3 METs

  30. Question # 11 • Who is exercising harder, Fred or Pete? • Fred(72 kg) • VO2 = (0.2x160.8) + (0.9x160.8x0.1)+3.5 • VO2 = 32.16 + 14.47 + 3.5 • VO2 = 50.13 mLkg-1min-1 or 14.3 METS • Pete (55 kg) • Power = 2.5kg x 6m x 60rpm= 900 kgmmin-1 or 150 watts • VO2 = (10.8 x 150)/55 + 7 = 36.45 mLkg-1min-1 or 10.4 METS • FRED is working harder

  31. Question # 12 • Desired exercise intensity = 8 METs; what is the grade at 3 mph • 3 mph x 26.8 mmin-1 per MPH = 80.4 mmin-1 • 28 mLkg-1min-1 = (0.1x80.4) + (1.8x80.4xG) + 3.5 • 28 = 8.04 + 144.7(G)+ 3.5 • 16.46 = 144.7 (G) • G= 11.4%

  32. Question # 13 • Functional capacity of 70 kg male completing stage 5 (3mph/12%) of Balke protocol. • 3 mph = 80.4 mmin-1 • VO2 = (0.1x80.4) + (1.8x80.4x0.12)+3.5 • VO2 = 8.04 + 17.37 + 3.5 • Relative VO2 = 28.9 mLkg-1min-1 or 8.3 METs • Absolute VO2 = 2023 mLmin-1 or 2.02 Lmin-1

  33. Question # 14 • MET level of man running @ 7mph and 5% grade • 7 mph = 187.6 mmin-1 • VO2 = (0.2x187.6)+(0.9x187.6x0.05)+3.5 • VO2 = 37.52 + 8.44 + 3.5 • VO2 = 49.46 mLkg-1min-1 or 14.1 METs

  34. Question # 15 • What is kcal utilization over 20 minutes on the cycle ergometer if VO2 = 1745 mLmin-1. • 1745 mLmin-1 = 1.75 Lmin-1 • 1.75 Lmin-1 x 5 kcalsL-1 = 8.75 kcalsmin-1 • 8.75 kcalsmin-1 x 20 min = 175 kcals expended over 20 minutes

  35. Questions

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