Energy Expenditure Flashcards
total energy expenditure
“Useful” work done + “wasted” work done
- useful = mechanical energy (ergometry)
- wasted = heat energy (direct and indirect)
calorimetry
measurement of heat liberated/absorbed in the metabolic process.
- directly: measure actual heat production
- indirectly: measure RER to estimate heat production
calorie
Basic unit of heat
(amount to raise 1g of water from 14.5C to 15.5C)
1 Cal = 1000 kcal/calories
1 kcal = 4186 J or 4.186 kJ
direct calorimetry
measures heat produced in respiration chamber
-limited usefulness
indirect calorimetry
a method of estimating energy expenditure by measuring respiratory gases
-open or closed circuit
open circuit indirect calorimetry
inhale room/atmospheric air
- measure O2 consumption and CO2 production
-need to know what is in the air
closed circuit indirect calorimetry
- Breathes 100% O2 from a spirometer of know volume
- Never mixes with ambient air
-cheaper option
second law of thermodynamics
When energy is changed from one form to another, some useful energy is always degraded into lower quality energy (usually heat)
hill realtionship
when energy is used to preform muscular work, heat is given off and O2 is consumed in a proportional relationship
- if we know O2 consumption we can guess heat and this total energy expenditure
Relationship between heat, work, VO2
O2 consumption (l/min) during rest or activity allows for direct estimation of total energy expenditure
heat (from VO2) + mechanical energy = Total energy expenditure
VO2 and VCO2
atmospheric O2 = 20.9% CO2 = 0.03% N= 79.04%
CO2 (consumed = ViO2 - VeO2
VCO2 (pro.) = VeCO2 - ViCO2
Douglas Bag method
air exhaled into bag, changed out every minute, put in machine to tell how much O2 and CO2
Bengt Saltin
A “father” of exercise phys
-studied human muscle fiber type
-conducted “bed-rest” study
computerized metabolic system
-known gas [] in the air
-known gas volume (3L)
-known barometric pressure, temperature, humidity
- calibrate pre- and post- test
factors influencing gas volumes
Boyle’s Law
Charles’ Law
STPD
Boyle’s Law
as pressure increases, volume decreases (and vise versa)
Charles’ Law
As temperature increases, volume increases (and vise versa)
STPD
Standard Temperature Pressure Dry
- need some type of standardization due to global studies and thus differences in elevation, temp, humidity
Carbohydrates during exercise
C6H12O6 + 6O2 -> 6H2O + 6CO2
-6O2 consumed, 6 CO2 made = RQ of 1.0
fats during exercise
C12H32O2 + 23O2 -> 16CO2 + 16H2O
-23 O2 consumed, 16 CO2 made RQ=0.7
- fats need more O2 to fully metabolize
protein during exercise
AA used in metabolic pathway for energy (via transamination and deamination)
-RQ = negligible (~0.82)
respiratory exchange ratio (RER)
measurement of CO2 made and O2 consumed at mouth level (open circuit spirometry)
RER = VCO2/VO2
- RER > 1.0 = anaerobic respiration (more CO2 made than O2 consumed)
RER vs RQ
RER: co2 expired/ o2 consumed at mouth
RQ: Co2 produced by cell metabolism/ o2 used by tissues
- measure at steady state (if not and there is intensity increase RQ will be higher due to lag time to get to RER)
factors influencing RER measurements
- exercise intensity
- hyperventilation
- recovery
- diet
exercise intensity (influencing RER)
RER can be higher than 1.0 (more CO2 than O2) because H is made in exercise then buffered w bicarbonate to make H2O and CO2 that is excess “non metabolic”
Hyperventilation (influencing RER)
increased VO2 = increase RER
- psychological stress/nerves
-exercise anticipation
recovery (influencing RER)
VO2 drop rapidly when cease exercise w VCO2 still high RER increase (short term recovery)
then CO2 is retained resulting in lower RER (long term)
using indirect calorimetry
-all indirect measurements involve error
- VO2 must be steady state so RQ=RER
-assume protein metabolism is negligible
-recovery energy also contribute to total energy
METs
1 Metabolic equivalent = energy expenditure while sitting/resting
- 1 MET = 3.5ml O2kgmin (max 13 /per person)
- used by clinician to express energy cost activities
energy expenditure efficiency
-RMR/BMR = 60-75%
- thermogenesis = 10%
- TEA
- non exercise activity thermogenesis
Economy of walking and running
O2 cost needed to maintain a given velocity of movement; the lower is better
efficiency
mechanical efficiency (%) is reflective of the “useful” mechanical work done in relation to “chemical” ATP expended
Gross ME =(workoutput/total EE)(100)
gross vs net vs delta efficiency
gross: include EE in denominator
net: subtracts resting EE from denominator (>GME)
delta: changes in efficiency btwn workloads
factors influencing economy
age
MSK differences
body mass
skill/technical issues (better = improved efficiency)
activity type/intensity (high intense less effective)
fitness level (more fit = more efficient)
environmental conditions
equipment/engineering
age (influencing efficiency)
kids and elderly less economic especially running
- kids have high BMR, SA:mass, immature running, less effective ventilations, lower anaerobic capacity
- elderly have more MU recruitment, gait instability, antagonistic co-contractions
musculoskeletal differences (influencing efficiency)
- more ST fibers = more efficiency (more ATPase)
- body structure and flexibility are important
body mass (influencing efficiency)
greater lean body mass = more EE = less efficient
more overall body mass means greater EE for WB activity and less efficiency
