Resting Metabolic Rate (RMR)
How Do You Measure
ENERGY EXPENDITURE?
Metabolic Rate in Various Conditions
• Basal Metabolic Rate (BMR)
Minimum energy required to sustain life
(Measured when Waking State with No Food & No Movement)
• Resting Metabolic Rate (RMR)
Combination of…
Basal Metabolism (waking state)
Sleeping Metabolism
Arousal Metabolism
• Exercise Metabolic Rate
Metabolism during Exercise + RMR
How Do You Measure Metabolic Rate?
Method #2
INDIRECT CALORIMETRY
Substrate (CHO or Fat) + O2 + Energy (ATP)

CO2 + H2O + Energy (ATP) + Heat
Method #1
DIRECT CALORIMETRY
Method #1
DIRECT CALORIMETRY
Total Energy from Metabolism...
~40%  ATP
~60%  Heat
So…
if you measure your body’s heat production,
you can estimate energy production!
DIRECT CALORIMETRY
How Does It Work?
Insulated
Chamber
Heat
Exchanger
Water flow in the heat exchanger
The difference in the temperature of water entering and
leaving the chamber reflects the person’s heat production.
DIRECT CALORIMETRY
Problems
•
•
•
•
Expensive
Not applicable in most activities
Highly impractical for large-scale studies
Very few pieces of equipment in nation
So…Method #2 
Method #2
INDIRECT CALORIMETRY
Complete Combustion of Food
IS
Achieved at the Expense of O2 Molecules.
So…
if you measure your oxygen uptake,
you can estimate energy production!
INDIRECT CALORIMETRY
How Does It Work?
O2
Inspired
Oxygen Uptake
= (VO2 IN) – (VO2 OUT)
O2
Expired
INDIRECT CALORIMETRY
Haldane Transformation
Assumptions
1. Ambient Air
– FIO2 = 20.93% = 0.2093
– FIN2 = 79.04% = 0.7904
– FICO2 = 0.03% ~ 0 (ignore it)
2. FIN2 + FIO2 = 1
3. FEN2 + FEO2 + FECO2 = 1
4. VI*FIN2 = VE*FEN2 (N2 is inert gas)
INDIRECT CALORIMETRY
Haldane Transformation
VO2 = (VI*FIO2) – (VE*FEO2)
VI*FIN2 = VE*FEN2
VE*FEN2
VI =
FIN2
VE* [1 – (FECO2 + FEO2)]
VI =
FIN2
VO2 = VE
1 – (FECO2 + FEO2)
0.7904
X 0.2093 – FEO2
Respiratory Quotient (RQ)
RQ =
CO2 produced
O2 consumed
At the CELL
Each substrate has its own RQ value.
(carbohydrates (1.0) vs fatty acids (0.7)?)
RQ for CHO and FAT
Carbohydrate (Glucose):
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
RQ = 6CO2 / 6O2 = 1.00
Fat (Palmitic Acid):
C16H32O2 + 23O2  16CO2 + 16H2O + Energy
RQ = 16CO2 / 23O2 = 0.70
What about Protein?
• Protein is metabolized as either fat or
carbohydrate and is therefore difficult to
separate from the other two
• Protein consumption is a small percentage
of total metabolism during normal
conditions and can be ignored
Respiratory Exchange Ratio (RER)
CO2 produced
RER =
O2 consumed
At the
LUNGS
Actual gas exchange (RER) at the lungs can be
greater or less than the RQ at the cell. It can
range from slightly below 0.7 all the way to
around 1.5 (lots of non-metabolic CO2)
(hyperventilation vs hypoventilation?)
How Do You Use RQ or RER?
Assuming RQ = RER,
you can estimate
the energy produced per liter of O2.
e.g.
RQ = 0.85  4.86 kcal/LO2
(Utilizing 50.7% CHO & 49.3% Fat)
 Table 4.4
Comparing RMR
• Absolute Oxygen Uptake (in LO2/min)
more muscle mass
 higher absolute VO2
Not able to compare
300 lbs football player and 130 lbs X-country runner
• Relative Oxygen Uptake (in mlO2/kg/min)
Eliminates some of the differences in muscle
mass by using body mass (body
composition is unaccounted for)
Metabolic Equivalent (MET)
A MET is defined as a multiple of the
Resting Metabolic Rate.
e.g.
If RMR (1 MET) = 3.6 mlO2/kg/min,
Work requires 7.2 mlO2/kg/min of O2 uptake = 2 METS
(# of METS in different activities?)
STPD Correction Factor
STPD:
Volume of Gas expressed under Standard Conditions of
–
–
–
Temperature (273K or 0°C)
Pressure (760 mmHg or 1 atm)
Dry (no water vapor)
STPDCF =
273K
PBAR – PH2O
X
273K + TA (in °C)
760 mmHg
(hot, wet condition vs cold, dry condition?)