Metabolic Calculations - Purpose Estimate energy expenditure during steady state exercise.
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Transcript of Metabolic Calculations - Purpose Estimate energy expenditure during steady state exercise.
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Metabolic Calculations - Purpose
Estimate energy expenditure during steady Estimate energy expenditure during steady state exercisestate exercise
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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.
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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 PLACESMonark Cycle Work Rate: Resistance X Revs/min x 6m/revMonark Arm Work Rate: Resistance X Revs/min x 2.4m/rev
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• 1L= 1000 mL• 1kg= 2.2 lbs• 1mph= 26.8 mmin-1
• 1 MET = 3.5 mLkg-1min-1
• 1 W= 6 kgmmin-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 O2min-1 = 5 kcalmin-1
• 1 lb of fat= 3500kcal
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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
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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.
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Met Calc - Key Points
• Estimates oxygen requirement (VO2) for various workloads– Linear relationship– Some variability
(S.E.E. 7%)
assumptions
500
1000
1500
2000
2500
0 50 100 150 200
Watts
VO
2 (
ml/m
in)
S.E.E. 7%
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Met Calc - Key Points (con’t)
• “Steady State” or submax exercise:O2 cost = O2 uptake
• “Maximal” ExerciseO2 cost > O2 uptake
O2 R
equirement
Workload
AnaerobicComponent
Max Exer
=
VO2max
Predicted
VO2max
you cannot predict maximal
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Met Calc - General Principle
MechanicalWorkload
MetabolicEquivalent
• Meters.min-1
• kgm.min-1
• VOVO22
• METs• kcals.min-1
We estimate one value based onWe estimate one value based onknowledge of the otherknowledge of the other
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Metabolic Units
Gross vs. NET
All equations give Gross VO2 values.
For weight loss use the NET VO2 vales.
NET: Gross – resting valueVO2 NET : 40 ml/kg/min – 3.5 ml/kg/min = 36.5 ml/kg/min
OR
: 11.4 METS – 1 MET = 10.4 METS
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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 PLACESMonark Cycle Work Rate: Resistance X Revs/min x 6m/revMonark Arm Work Rate: Resistance X Revs/min x 2.4m/rev
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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
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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 + 7.20 + 3.5
• VO2 = 18.74 ml.kg-1.min-1
• VO2 = 18.74 ml.kg-1.min-1 / 3.5 = 5.4 METS
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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/minVO2 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
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ACSM Leg Cycling Equation
• Loads 300-1200 kgm/min; 50-200 wattsWork Rate = kg x meters/rev x RPM
Use 6 meters/revolution for the Monark Ergometer
Add resting twice : 1 for resting and 1 for unloadedQ: 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 kgmVO2 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
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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
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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
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ACSM Stepping EquationQ: 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 + 3.5VO2stepping = 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?
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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