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Metabolic Calculations - Purpose

Metabolic Calculations - Purpose. Estimate energy expenditure during steady state exercise. Importance of Metabolic Calculations. It is imperative that the exercise physiologist is able to interpret test results and estimate energy expenditure. Optimizing exercise protocols.

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Metabolic Calculations - Purpose

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  1. Metabolic Calculations - Purpose Estimate energy expenditure during steady state exercise

  2. Importance of Metabolic Calculations • It is imperative that the exercise physiologist is able to interpret test results and estimate energy expenditure. • Optimizing exercise protocols. • Exercise prescription. • Weight loss.

  3. Metabolic Calculations (S=Speed in m/min; G= % Grade) MODE Horizonal + Vertical + Rest • Walking VO2 = (0.1• S) + (1.8 • S • G) + 3.5 • Running VO2 = (0.2• S) + (0.9 • S • G) + 3.5 • Cycle VO2 = 1.8 (work rate) + 3.5 + 3.5 Body Weight (kgs) • Arm VO2 = 3 (Work Rate) + 3.5 Body Weight (kgs) • Stepping VO2 = (0.2• f) + (1.33 • 1.8 • h • f) + 3.5 CARRY OUT EACH STEP TO 2 DECIMAL PLACES Monark Cycle Work Rate: Resistance X Revs/min x 6m/rev Monark Arm Work Rate: Resistance X Revs/min x 2.4m/rev

  4. 1L= 1000 mL 1kg= 2.2 lbs 1mph= 26.8 mmin-1 1 MET = 3.5 mLkg-1min-1 1 W= 6 kgmmin-1 1 in = 0.0254m=2.54 cm Pace: min/mile to mph = 60/time Ex: 7.5 min/mile / 60 min/hr = 8mph Kcal/min = METS * 3.5 * BW 200 1L O2min-1= 5 kcalmin-1 1 lb of fat= 3500kcal

  5. Metabolic Calculations (S=Speed; G=Grade) • Walking (most accurate from 1.9-3.7 mph) • VO2 = (0.1• S) + (1.8 • S • G) + 3.5 • Treadmill and Outdoor Running (for speeds > 5 mph) • VO2 = (0.2• S) + (0.9 • S • G) + 3.5 • Leg Ergometry • VO2 = 1.8 (work rate)/(BM) + 3.5 + 3.5 • Arm Ergometry • VO2 = 3 (Work Rate)/(BM) + 3.5 • Stepping • VO2 = (0.2• F) + (1.33 • 1.8 • H • f) + 3.5 CARRY OUT EACH STEP TO 2 DECIMAL PLACES

  6. Assumptions and Limitations • Measured VO2 is highly reproducible at a given steady state workload. Failure to achieve steady state is an overestimation of VO2. • Accuracy of equations is unaffected by most environmental conditions such as heat and cold. • However, variables that change mechanical efficiency (gait abnormalities, wind, snow or sand) result in a loss of accuracy. • Assumption that ergometers are calibrated and no holding on to hand rails occur during on treadmill.

  7. Met Calc - Key Points • Estimates oxygen requirement (VO2) for various workloads • Linear relationship • Some variability (S.E.E. ­ 7%) assumptions S.E.E. ­ 7%

  8. Met Calc - Key Points (con’t) Anaerobic Component • “Steady State” or submax exercise: O2 cost = O2 uptake • “Maximal” Exercise O2 cost > O2 uptake = Predicted VO2max VO2max O2Requirement Max Exer Workload you cannot predict maximal

  9. Met Calc - General Principle Metabolic Equivalent Mechanical Workload • Meters.min-1 • kgm.min-1 • VO2 • METs • kcals.min-1 We estimate one value based on knowledge of the other

  10. Metabolic Units Gross vs. NET All equations give Gross VO2 values. For weight loss use the NET VO2 vales. NET: Gross – resting value VO2NET : 40 ml/kg/min – 3.5 ml/kg/min = 36.5 ml/kg/min OR : 11.4 METS – 1 MET = 10.4 METS

  11. Metabolic Calculations (S=Speed in m/min; G= % Grade) MODE Horizonal + Vertical + Rest • Walking VO2 = (0.1• S) + (1.8 • S • G) + 3.5 • Running VO2 = (0.2• S) + (0.9 • S • G) + 3.5 • Cycle VO2 = 1.8 (work rate) + 3.5 + 3.5 Body Weight • Arm VO2 = 3 (Work Rate) + 3.5 Body Weight • Stepping VO2 = (0.2• f) + (1.33 • 1.8 • h • f) + 3.5 CARRY OUT EACH STEP TO 2 DECIMAL PLACES Monark Cycle Work Rate: Resistance X Revs/min x 6m/rev Monark Arm Work Rate: Resistance X Revs/min x 2.4m/rev

  12. ACSM Walking Equation • Speeds ­ 50-100 m/min; 1.9-3.7 mph • (1 mph = 26.8 m/min) • “Relative” VO2 unit (ml/kg/min; ml.kg-1.min -1) VO2 walking = Horizontal Walking (HW) + Vertical Climb (VC) + Resting VO2 walking=Speed (m/min)x 0.1 + % grade x Speed (m/min)x 1.8 + 3.5

  13. ACSM Walking Equation • Example: VO2 for walking @ 3.0 mph at 5% grade • Convert 3.0 mph to m/min • 3.0 x 26.8 = 80.4 m/min VO2 walking = Horizontal Component + Vertical Component + Resting VO2 walking = Speed (m/min)x 0.1 + % grade x Speed (m/min)x 1.8 + 3.5 • VO2 = 80.04 x 0.1 + 80.04 x .05 x 1.8 + 3.5 • VO2 = 8.04 + 7.2 0 + 3.5 • VO2 = 18.74 ml.kg-1.min-1 • VO2 = 18.74 ml.kg-1.min-1 / 3.5 = 5.4 METS

  14. ACSM Running Equation • Speeds > 134 m/min; > 5.0 mph (1 mph = 26.8 m/min) VO2 for running at 6.0 mph at a 5% grade • Convert 6.0 mph to m/min • 6.0 x 26.8 = 160.8 m/min VO2 running = Horizontal Component + Vertical Component + Resting VO2 running = Speed (m/min)x 0.2 + % grade x Speed (m/min)x 0.9 + 3.5 VO2 running = 160.8x 0.2 + 0.05 x 160.8x 0.9 + 3.5 VO2 running = 32.16 + 7.24 + 3.5 VO2 running = 42.9 ml/kg/min VO2 running = 42.9 ml/kg/min / 3.5 = 12.26 METS

  15. ACSM Leg Cycling Equation • Loads 300-1200 kgm/min; 50-200 watts Work Rate = kg x meters/rev x RPM Use 6 meters/revolution for the Monark Ergometer Add resting twice : 1 for resting and 1 for unloaded Q: What is the VO2 for a 90 kg subject pedaling at 2.0 kgs at 60 rpms Work Rate: 2.0 kg x 6 m/rev x 60 rpms = 720 kgm VO2 Cycling = 1.8x WR+ 3.5 + 3.5 BW VO2 Cycling = 1.8x 720+ 3.5 + 3.5 90 kgs VO2 Cycling = 14.4 + 3.5 + 3.5 VO2 Cycling = 21.4 ml/kg/min or 6.1 METS

  16. ACSM Arm Cycling Equation • Loads 150 to 750 kgm/min; 25-125 watts • 3.0 = ml.min-1 per kpm/min ( from leg cycling) • Only 1 resting component (3.5) • Monark™ Rehab Trainer: 2.4 meter/rev Work Rate: kg x 2.4 meters/rev x rpm Q: What is the VO2 of a 100 kg person who uses a Monark arm ergometer at 3 kg at 50 rpms. Work Rate: 3 kg x 2.4 meters/rev x 50 revs/min = 360 kgm • VO2 arm= 3x WR + 3.5 ml.kg-1.min-1 BW • VO2 arm= 3x 360 + 3.5 ml.kg-1.min-1 = 14.3 ml/kg/min 100

  17. ACSM Stepping Equation • VO2stepping = 0.2 x f + 1.33 x 1.8 x h x f + 3.5 • VO2 varies with Step height & rate • “Relative” VO2 unit (ml.kg-1.min-1) • VO2 (ml.kg-1.min- 1 ) = Horizontal + Vertical + Resting • Horizontal = steps/min x 0.2 • Vertical= step ht x steps/minx 1.33 x 1.8 • Down cycle ­ 0.33 VO2 of the up cycle (add this in by multiplying by “1.33”) • 1.8 is the constant for vertical work • Step height is entered in meters • 1 in = 0.0254m=2.54 cm

  18. ACSM Stepping Equation Q: What is the VO2 for a 55 kg woman who is stepping on a 12” bench at 30 steps per minute • Calculate step height in meters • 12” x 0.0254 = 0.31 meters VO2stepping= 0.2 x f + 1.33 x 1.8 x h x f + 3.5 VO2stepping = 0.2 x 30 + 1.33 x 1.8 x 0.31 x 30 + 3.5 VO2stepping= 6 + 22.26 + 3.5 VO2stepping=31.76 ml/kg.min VO2stepping = 31.76/3.5 = 9.1 METS Question: What is the kcal expenditure (kcal.min-1) for this 55 kg person exercising at the above VO2 or METS? This person exercises at this rate 3 times per week for 30 minutes each session. How long will it take this person to lose 10 pounds exercising at this rate?

  19. Kcal conversion example Q: What is the kcal expenditure (kcal.min-1) for a 55 kg person exercising at an oxygen uptake of 9.1 METs? This person exercises at this rate 3 times per week for 30 minutes each session. How long will it take this person to lose 10 pounds exercising at this rate? kcal.min-1 = METs x 3.5 x BW (kg) 200 kcal.min-1 = 8.1 x 3.5 x 55 (Why did we use 8.1 METS?) 200 (For weight loss use the NET) kcal.min-1 = 7.8 1 pound of fat = 3,500 kcals 10 pounds = 35,000 kcals Answer:35,000 kcals = 4,487.18 minutes 7.8 kcals/min 4,487.18 minutes = 49.9 weeks 90 minutes/week

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