Measuring Energy Expenditure Flashcards
calorimetry measures
heat energy liberated in metabolic processes
basic unit of heat
calorie
function of a calorie
raise 1 gram of water by 1 degree
1kcal= how many kj?
4.186
Total daily energy expenditure includes (3)
basal/resting metabolic rate
thermogenesis
exercise/activity energy expenditure
basal metabolic rate
sleeping - energy required for body’s vital functions
resting metabolic rate
energy expended while resting quietly (supine)
total daily energy expenditure is proportional to
work done and heat produced
Macronutrients + O2 =
ATP for mechanical work and heat
thermogenesis
thermal effect of food - heat through metabolization of the food
body heat production can be measured with
whole body calorimeters
Heat production + work completed in calorimeter =
TEE
limitations of whole body calorimeters
expensive
error due to
- heat produced by ergometer
- thermoregulation - body can act as a reservoir of heat, which can be affected by body composition/ind variability
Atwater and Rosa used a whole body calorimeter to establish that
oxygen consumption is proportional to energy expenditure
experimental findings and therefore?
direct heat measurement - 2723 kcal
gas analysis - 2717 kcal
difference of 0.2%
we can measure oxygen consumed we can indirectly determine energy expenditure (from both muscular work and heat production)
every litre of oxygen consumed is equal to
5kcal burned, precise number depends on the specific type of macronutrient
food +o2 =
co2 and h2o and energy
how do you know what you’re burning?
Respiratory quotient - ratio of amount of CO2 produced divided by the amount of oxygen consumed at the cellular level
C6H12O6 needs ___ to produce _____
6 O2 to get 6 CO2 and 6 H2O
RQ of glucose
6CO2/6O2 = 1
amount of O2 required and CO2 produced for the oxidation of carbs
equivalent
RQ for fat
a molecule of fat is less oxidized (higher ratio of carbon to oxygen) - more oxygen is required to oxidize fat RQ<1
Palmitic FA RQ
C16H32O2+ 24O2=16CO2 +16H2O
16/24=0.67
What is not a major source of energy during rest and submax exercise
proteins
proteins are catabolized into
AA
Average RQ of AA is
0.85
what is RQ for protein largely ignored by exercise physiologists
little protein is used as a source of energy during exercise
RER
respiratory exchange ratio
- CO2/O2at mouth
RQ vs RER
same at rest and during steady state submaximal exercise
RER depends on and ranges from
intensity of exercise, 0.7 (all fat) -1.0 (all carbs, greater than 1, hydrogen buffering
RER lvls have an assigned
caloric equivalent value
hydrogen buffering
lactate and hydrate needed bicarbonate to get rid of it, production of more co2 which can mess with things to affect the ratio and slightly anaerobic
how do we measure oxygen consumed and CO2 produced
spirometry - indirect calorimetry method for estimating heat production in which expired air is measured and analyzed for the amount of O2 consumed and CO2 produced Closed system (air out of a tank, not usually) and open circuit spirometry (breath in room air and analyze the composition and volume of air that you breathed out)
composition of atmosphere air
oxygen -21%
CO2 - .03%
N2 - 79%
open circuit indirect calorimetry/spirometry uses _____ to measure
computerized metabolic(metabolic cart) for
- volume of air expired
- % of O2 and CO2 in expired air
how to determinate oxygen consumption with open circuit indirect calorimetry/spirometry
it is the amt of oxygen taken up, transported and used at the cellular level
VO2 = volume inspiredfraction O2-volume expiredfraction O2 volume
how to determine CO2 produced
amt of CO2 generated during metabolism
VCO2 = volume expiredfraction CO2-volume inspiredfraction CO2
how do we determine volume inspired
volume of air inspired vs expired are slightly diff
- haldane transformation (VFIN2-VFEN2)
because N2 is not used in metabolism (inert gas) so we can use the ratio of nitrogen inspired /expired to obtain original volume
gas volume as affected by barometric pressure, temp, and water vapour
increase pressure - decreased volume (boyles law)
increased temperture - increased air volume (charles law)
increased humidity - increased air volume
why standardize spirometry?
permit VO2 results in different settings - normalize VE to STPD - standard temperature pressure dry
273 kelvin or 0 degrees, 700mmhg, normalized effects of humidity
we measure CO2 and O2 to
see their kcals
prior to using the metabolic cart the machine must be
calibrated
- O2 and CO2 sensors calibrated with standardized gas mix
- known gas volume used to calibrate volume of air so accurate VE measures are obtained (large syringe)
portable metabolic carts for
running, swimming, animals
douglas bags
breathing tubes with valves to analyze air flow out of lungs
How does RER increase and what does it mean?
increase of intensity to increase Carb utilization
low intensity and RER
low RER and high utilization of fat
liver glycogen is high during (2)
high intensity short and moderate duration
RER and RQ are equal when?
under rest and sub max exercise
3 situations when
1- bicarbonate buffering during high intensity exercise - elevated CO2 production RER bigger than 1
- anticipatory response to exercise - hyperventilation results in increased VCO2 increasing RER
- Recovery - decrease in ventilation (hypoventilation) and restoration of blood bicarbonate conc. resulting in decreased VCO2 relative to VO2, decreased RER
MET
metabolic equivalent
- amt of energy used for resting metabolism
1MET = 3.5mlO2 /(min*kg)
no additional stress or activity factors for normal body weight of 25-30BMI
activities and MET
multiples of MET - asses someone’s energy expenditure
double labeled water
12-17 day period objective measure of energy expenditure -
deuterium and O18 to indirectly measure energy expenditure
H leaves as water whereas O leaves as water and CO2, difference in the loss of O and H lets you calculate the CO2 produces
