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The Use of Metabolic Equations in Exercise Prescription. Conversions and Calculations. Objective. To enable the participant to calculate oxygen uptake in METS and ml/kg/min and determine caloric expenditure for various activities. The Value of Metabolic Math. Follow progress over time
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The Use of Metabolic Equations in Exercise Prescription Conversions and Calculations
Objective • To enable the participant to calculate oxygen uptake in METS and ml/kg/min and determine caloric expenditure for various activities
The Value of Metabolic Math • Follow progress over time • Determine the maximal response to an exercise bout • Prescribe appropriate exercise intensity on various modalities • Determine workload at any point in an exercise session • Determine energy expenditure
What is Metabolism? • The sum of all chemical processes that occur within the body to allow for normal function • Metabolic Rate - the rate at which the body consumes oxygen and produces energy • Rest = ~1MET = 3.5ml/kg/min
Metabolic Measurements • 1. Oxygen Consumption • 2. Kcals • 3. Work • 4. Power
Oxygen Consumption • A measure of aerobic fitness • A measure of volume of oxygen • Measured through maximal tests or predicted by measuring physiological variables • expressed in liters/min or ml/kg/min
Kcals • A measure of energy transfer (kilocalorie) • The amount of energy necessary to raise the temperature of 1kg of water 1ºC • For every liter of O2 consumed ~5kcal are expended • RER + 4 is more precise
Work • A measure of the amount of force over a given distance • Work = Force x Distance • Expressed in kgm or Nm
Power • Work÷Time (Force x Distance÷Time) • Expressed in kgm/min (kpm/min) or Watts • 1Watt=6.12 kgm/min
Conversions • 1. Distances • 2. Speeds • 3. Weights • 4. Volumes • 5. Work Units • 6. Workload Units • 7. Nutritional Units
Distances • 1mile=1.62km • 1km=0.62mile • 1mile=5280feet • 1km=1000meters • 1m=3.28ft • 1m=100cm • 1inch=2.54cm • 1inch=0.0254m
Speeds • 1mph=26.8m/min • 1mph=1.62km/hr • 1km/hr=0.62mph
Weights • 1kg=2.2046lbs • 1kg=9.8N • 1kg=1000g
Volumes • 1oz=29.57ml • 1qt=1.11L • 1L=1000ml
Work Units • 1 MET=3.5ml/kg/min • 5kcal per Liter of O2/min • 1ft.lb=1.356Nm
Workload Units • 1Watt=6.12 kgm/min • 1kgm/min=.1635 Watts • 1.8 ml O2/kg/min per 1m/min • 1.8 ml O2 consumed per 1kgm (leg) • 3ml O2 consumed per 1kgm (arm_ • .2 ml O2 per 1step/min
Nutritional Units • 4kcal per gram carbohydrates • 4 kcal per gram protein • 9 kcal per gram fat • 4 kcal per gram alcohol
Metabolic Calculations • Three components of the Metabolic Equation • resting component • horizontal component • vertical component
Walking • Rest = 3.5 ml/kg/min • Horizontal = m/min x 0.1 ml O2 per m/min • 0.1 ml of O2 to transport each kg of body mass per meter of horizontal distance • Vertical = grade (fraction) x m/min x 1.8 • 1.8 ml of O2 per kg of body mass for each meter of vertical distance
Walking Equation • Equation: • VO2(ml/kg/min) = 0.1 (speed) + 1.8 (speed) (grade) + 3.5 • used for speeds of 50-100 m/min or 1.9-3.7 mph • Units: • (0.1ml/kg/meter)(meter/minute) + (1.8ml/kg/meter) (meter/min)(fractional grade) + 3.5 ml/kg/min
Running • Resting = 3.5 ml/kg/min • Horizontal = m/min x 0.2 O2 per m/min • Vertical = grade (fraction) x m/min x 0.9 • Equation: • VO2(ml/kg/min) = 0.2 (speed) + 0.9 (speed) (grade) + 3.5 • used for speeds >80 m/min if truly jogging
Leg Ergometry (Cycling) • Rest = 3.5 ml/kg/min • Unloading component = 3.5ml/kg/min (still have resistance even though pedaling with no resistance - like moving your hand through air) • Horizontal = none • Vertical = kgm/min x 1.8 • 1.8 ml of O2 per kg of body mass for each meter of vertical distance
Leg Ergometry Equation • Equation: • VO2 (ml/kg/min) = 1.8 (kgm/min)÷BW + 3.5 + 3.5 • used for 300-1200 kgm/min • Units: • (1.8ml/kg/meter)(kgm/min)÷(kg) + 7 ml/kg/min
Arm Ergometry • Resting = 3.5 ml/kg/min • No unloading component (negligible since arms have small mass) • Horizontal = none • Vertical = kgm/min x 3 • Equation: • VO2 (ml/kg/min) = 3 (kgm/min) ÷ BW + 3.5 • used for 150-750 kgm/min
Stepping • Rest - 3.5 ml/kg/min • Horizontal = .2 x steps/min • Vertical = m/step x steps/min x 1.33 x 1.8 • Equation: • VO2 (ml/kg/min) = 0.2 (steps/min) + (1.33 x 1.8 x m/step x steps/min) + 3.5 • 1.33 accounts for going up (1.0) and coming down (.33)
VO2max Equations • Bruce Treadmill (without handrails) • VO2max(ml/kg/min)= 14.8 - 1.379 (time in min) + 0.451 (time2) - 0.012 (time 3) • Bruce Treadmill (with handrails) • VO2max (ml/kg/min) = 2.282 (time in min) + 8.545
Cycle Ergometry • Males • VO2max(ml/min) = 10.51 (Watts) + 6.32 (BW kg) - 10.49 (age in yrs) + 519.3 • Females • VO2max(ml/min) = 9.39 (Watts) + 7.7 (BW kg) - 5.88 (age in yrs) + 136.7
Field Tests • Rockport Walking Test • VO2max(ml/kg/min) = 132.853 - 0.1692 (BW kg) - 0.3877 (age in yrs) + 6.315 (gender) - 3.2649 (time in minutes) • 1.5 Mile Run Test • VO2max(ml/kg/min) = 3.5 + 483÷time in minutes • 12 Minute Run • VO2max(ml/kg/min) = 3.126 x (meters in 12 min) - 11.3
Calculating kcals • VO2 in ml/kg/min • multiply by BW kg = ml/min • divide by 1000 = L/min • multiply by 5 = kcal/min • multiply by minutes of exercise = total kcals • multiply by # sessions = kcals over time • divide by 3500 = lbs of fat lost (assuming caloric balance)