Measurement of Energy Expenditure The unit of measurement for energy is the kilocalorie (kcal) –Quantity of heat necessary to raise the temp. of 1 kg (liter) of water 1 degree Celsius Direct method would be to measure the heat production of the body –Requires an instrument called a calorimeter –Large, expensive, not feasible

Estimate of Energy Expenditure There is a very good relationship between kcals of heat the body produces and the amount of oxygen the body uses Thus, measurement of oxygen uptake (VO 2 ) of the body is the indirect method for estimating energy expenditure –Estimates are within ± 1% –Requires oxygen analyzer and ventilation meter –Not always feasible

Estimate of Oxygen Uptake There is a good relationship between the mechanical work performed by the body and the amount of oxygen that is used Thus, we can predict (estimate) oxygen uptake (VO 2 ) of the body by knowing the amount of work that is performed - this can be considered a doubly indirect method for estimating energy expenditure

Mechanical Units - Force Force = mass x acceleration “Weight” ~ mass undergoing gravitation acceleration examples: lbs. and kgs Kilopond (kp) ≈ 1 kg mass under normal gravitational acceleration 1 kp ≈ 1 kg

Mechanical Units - Work Work = force x distance Units: –kilopond meters (kp. m or kpm) –kilogram meters (kg. m or kgm) –foot pounds (ft. lbs) Walking/Running ~ carrying our mass (body weight) a given distance (meters) and therefore we can determine the “work” performed

Mechanical Units - Power Power = Work / Time Units: –kilopond meters per min (kp. m. min -1 ) –kilogram meters per min (kg. m. min -1 ) –watts (1 watt ≈ 6 kg. m. min -1 )

Metabolic Calculations ACSM has developed equations to estimate VO 2 from work rates (power output) obtained on some common modes of exercise –Walking / running –Cycling (leg and arm) –Stepping As these give estimates of energy metabolism they are called Metabolic Calculations Appendix D of GETP7 (pp )

Met Calcs - General Principle Mechanical Work or Power Metabolic Equivalent kg. m kgm. min -1 VO 2 (L) VO 2 (L. min -1 ) We estimate one value based on knowledge of the other VO 2 (L. min -1 ) kcals. min -1

MET Calcs - Key Points “Steady State” or submax exercise –Energy required = O 2 uptake

MET Calcs - Key Points Estimates oxygen requirement (VO 2 ) for various work rates –Linear relationship – Remember estimate=error (S.E.E. ≈ 7%) This represents 2/3 of the population. Remember 1/3 will have an even larger error.

MET Calcs - Key Points Remember: “Steady State” exercise –Energy required = O 2 uptake “Maximal” Exercise –Energy required > O 2 uptake O 2 Requirement Workload Anaerobic Component Max Exer = VO 2max Predicted VO 2max

Metabolic Units Absolute vs. Relative VO 2 units Absolute –independent of body weight –non-weight bearing activities leg and arm cycling equations –Units are: liters of O 2 per minute ( l. min -1 ) –Or: milliliters of O 2 per minute (ml. min -1 )

Metabolic Units (cont.) Absolute vs. Relative V O2 units Relative –dependent on body weight –weight bearing activities walking, jogging, stepping equations –Units are: mls of O 2 per kg per minute –(ml. kg -1. min -1 )

Metabolic Units (cont.) METabolic equivalent –1 MET = resting energy requirement –Think in terms of multiples of resting level Expressing V O2 units in METs –1 MET = 3.5 ml. kg -1. min -1

Metabolic Units (cont.) 7th Ed. GETP version of all equations yield relative units (ml. kg -1. min -1 ) However... –e nergy expenditure applications are still based on absolute units (i.e., kcals. min -1 )

Metabolic Units (cont.) Gross vs. Net VO 2 or kcals “Gross” includes resting component “Net” refers to VO 2 above rest

Energy Conversions 1 liter O 2 ≈ 5.0 kcals 1 lb ≈ 3500 kcals 1 MET ≈ 1.0 kcals. kg. hr -1 Kcal. min -1 = METs x 3.5 x BW(kg) / 200 –ACSM Guidelines 7th Ed. p. 148

ACSM Metabolic Equations Regression equations a = intercept –“y” value when x = 0 b = slope of line –unit ∆ in “y”, for every one unit ∆ in “x” Y X b a Y Unit = oxygen cost X Unit = power output Y = a + bx

ACSM Walking Equation Speeds ≈ m/min ; mph “Relative” V O2 unit (ml/kg/min) V O2 = Horizontal + Vertical + Resting HC (ml/kg/min) = m/min x 0.1 VC (ml/kg/min) = % grade x m/min x 1.8 Resting (ml/kg/min) = 3.5. Combine Resting V O2 into HC component during the calculations.

RestVertical Component Horizontal Component ACSM Walking Equation Speeds ≈ m/min ; mph “Relative” VO 2 unit (ml/kg/min) VO 2 = Horizontal + Vertical + Resting VO 2 ml/kg/min = 0.1 (speed) (speed x grade) ACSM GETP7 Table D-1

“Gross” Kcal conversion example What is the “gross” kcal expenditure (kcal/min) for an 85 kg person exercising at an oxygen uptake of 5.3 METs? kcals/min = METs x 3.5 x BW(kg)/200 –ACSM Guidelines 7th Ed. p 148 kcals/min = kcals/min ≈

“Net” Kcal conversion example What is the “Net” kcal expenditure (kcal/min) for an 85 kg person exercising at an oxygen uptake of 5.3 METs? Net VO 2 = Gross VO 2 - Rest VO 2 Net VO 2 = 5.3 METs - 1 MET = 4.3 METs –kcals/min = METs x 3.5 x BW(kg)/200 –kcals/min = –kcals/min ≈

ACSM Weekly kcal threshold (p. 151) “Minimum” caloric threshold ≈ 1000 kcals Based on “NET” kcals/min = 6.4 Minutes of exercise?: 1000/6.4 = 156 –3 Workouts: 156/3 = 52 min. –4 Workouts: 156/4 = 39 min. –6 Workouts: 156/6 = 26 min. This was for an 85 kg 5.3 METs Achieving the “minimal” kcal threshold

RestVertical Component Horizontal Component ACSM Running Equation Speeds > 134 m/min ; 5.0 mph “Relative” VO 2 unit (ml/kg/min) VO 2 = Horizontal + Vertical + Resting VO 2 ml/kg/min = 0.2 (speed) (speed x grade) + 3.5

ACSM Leg Cycling Equation Loads kgm/min ; watts –Remember 1 watts = 6 kgm/min Need to obtain work rate (Power output) –Electrical cycles usually give Watts –Mechanical cycles need to know resistance, flywheel distance, and pedal rate Kgm/min = kg x meters/rev x RPM

Work Rate determination Monark bike: most common testing ergometer Resistance (force) settings in kp or Kg Standardized distance of flywheel –6.0 meter/rev Rate (time): revolutions per minute (rpm)

ACSM Leg Cycling Equation (p. 289) VO 2 ml/kg/min = 1.8 (work rate)/M + 7 – Work rate in W – M = body mass in kgs – 7 = resting component (1 MET) ml/kg/min for unloaded pedaling

ACSM Leg Cycling Equation (p. 289) VO 2 ml/kg/min = 1.8 (work rate)/M + 7 – Work rate in kgm/min – M = body mass in kgs – 7 = resting component ml/kg/min for unloaded pedaling

Different Body Weights? Compare “relative” VO 2 during leg cycling at 600 kpm/min for 80 kg vs. 60 kg persons 80 kg ~ 5.9 METs 60 kg: 7.1 METs –ml/kg/min = 1.8(600)/ –ml/kg/min = 1080/ –ml/kg/min = 25.0 –25/3.5 = 7.1 METs > 1.2 METs for lighter person

Absolute VO 2 = for different body weights? What is the “absolute” VO 2 during leg cycling at 600 kpm/min for 80 kg vs. 60 kg persons Units? Ml/min Parts of the equation (600)/ ml/kg/min (600) = 1080 ml/min (not consider weight) - This is the same for both 60 and 80 kg persons

ACSM Arm Cycling Equation Appropriate for power outputs of 150 to 750 kgm/min ; watts These “loads” would be “Absolute” requirements i.e. VO 2 unit (ml/min) However, the equation converts them to relative by using body weight (VO 2 ml/kg/min )

ACSM Arm Cycling Equation Two versions of equation depending on expression of work rate VO 2 ml/kg/min = 3.0 (Kgm/min ) / M Kgm/min = kg x meters/rev x RPM –Monark Rehab (arm) Trainer: 2.4 meter/rev VO 2 ml/kg/min = 18.0 (W ) / M + 3.5

ACSM Arm Cycling Equation Most commercial units are designed to provide load settings in WATTs –In which case you can use the “watt” equation Others will usually provide charts that describe kgm/min loads at fixed RPMs –In which case you can use “kgm/min” equation Many “patients” exercise at loads below the lower end of equation range (i.e., < 150 kgm/min)…...

ACSM Stepping Equation VO 2 varies with Step height & rate VO 2 (ml/kg/min) = Horizontal + Vertical + Resting HC = 0.2 stepping rate VC = 1.33 x 1.8 x step height x stepping rate –Down cycle ≈ 0.33 VO 2 of the up cycle (add this in by multiplying by “1.33”) –1.8 is the O 2 constant for vertical work –Step height is entered in “meters” Resting = 3.5

Uses for Stepping Equation ?? Step Testing (submaximal CRF test) –Be sure subjects are doing a true “submax test” Step Aerobics –2-4-6 bench heights are standard –Music tempo will give step rate Step Machines ??? –Stair master, cybex, alpine etc