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Metabolic Calc posting for students Spring 2011

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Metabolic Calc posting for students Spring 2011 Powered By Docstoc
					    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.
 • Exercise prescription.
 • Weight loss.
   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
•    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
                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
     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.
        Met Calc - Key Points
• Estimates oxygen
                                          2500
  requirement (VO2) for                              S.E.E. - 7%
  various workloads                       2000




                           VO2 (ml/min)
   – Linear relationship
                                          1500
   – Some variability
     (S.E.E. - 7%)                        1000

                                          500
     assumptions                                 0     50    100    150   200
                                                            Watts
    Met Calc - Key Points (con’t)
• “Steady State” or                                 = Anaerobic
                                                      Component
  submax exercise:
                                                         Predicted
  O2 cost = O2 uptake



                        O2 Requirement
                                                         VO2max
• “Maximal” Exercise                                      VO2max
  O2 cost > O2 uptake

                                                    Max Exer



                                         Workload
 you cannot predict maximal
  Met Calc - General Principle

 Mechanical                 Metabolic
 Workload                   Equivalent

• Meters.min-1           • VO2
                         • METs
• kgm.min-1              • kcals.min-1

     We estimate one value based on
         knowledge of the other
               Metabolic Units
Gross vs. NET
All equations give Gross VO2 values.
For weight loss use the NET VO2 vales.
NET: Gross – resting value
VO2 NET : 40 ml/kg/min – 3.5 ml/kg/min = 36.5 ml/kg/min
OR
        : 11.4 METS – 1 MET = 10.4 METS
   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
          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
            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
                  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 =   160.8 x 0.2 + 0.05 x 160.8 x 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
                    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 = 1.8 x WR + 3.5 + 3.5
                 BW
VO2 Cycling = 1.8 x 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
         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=   3 x WR    + 3.5 ml.kg-1.min-1
                BW
•   VO2 arm= 3 x 360   + 3.5 ml.kg-1.min-1 = 14.3   ml/kg/min



               100
          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/min x 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
          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.
                         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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posted:8/15/2012
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