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 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 requirement (VO2) for various workloads Linear relationship Some variability (S.E.E. ­ 7%) assumptions S.E.E. ­ 7%

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

Met Calc - General Principle Mechanical Workload Metabolic Equivalent Meters.min-1 kgm.min-1 VO2 METs 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 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. How long will it take this person to lose 10 pounds exercising at this rate?

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