Energy expenditure Flashcards
RER
ratio between co2 produced and o2 consumption
1 MET
energy required to cover resting metabolic rate
1 MET =
3.5ml/kg/min
EPOC
occurs to refuel cells
calorie
amount of energy to raise 1g of water by 1 degree
why measure energy expenditure
assess metabolic needs
fuel utilisation
thermic effects of food
assess economy
direct calorimetry
measure heat given off during exercise
pros of direct calorimetry
direct measure of heat
accurate for steady state measures
cons of direct calorimetry
expensive
slow to generate results
few in operation
RER for 1 molecule of glucose
1.0
RER for 1 molecule of palmitic acid
0.70
what does indirect calorimetry predict
substrate usage
benefits of indirect calorimetry
can detect changes with breath by breath system
easy to administer
fairly accurate for aerobic
direct assessment of gas exchange
Which fuel substrate costs the most oxygen per kilocalorie
fats
assumptions of indirect calorimetry
body o2 is constant
co2 exchange in lungs is proportion to release from cells
little contribution from protein
limitations of indirect calorimetry
values >1 won’t provide valid estimation
inaccurate approaching 1
gluconeogenesis from fat and AA <0.7
not appropriate outside range of 0.70-1
BMR over time
2-3% decrease over 10 years
decrease fat free mass
depression of metabolic activity of lean tissue
altered by change in body composition and physical activity
MET
multiples of RMR
VO2
200ml/min for average woman
250 men
2 met activity is
7ml/kg/min
Fat max
exercise intensity at which max fat oxidation is observed
why does fat max occurs
lower availability of plasma FFA
reduced entry of fatty acids into mitochondria
level of runners and VO2 max
slower recreational = 60-65% RER 0.9 CHO 68%
faster = 70-75% RER 0.95 CHO 84%
elite = 80-90% RER 2.02-2.10
mechanical efficiency
external work accomplished / energy expenditure
EPOC
delay in post exercise oxygen consumption
EPOC fast component
rapid decline in oxygen uptake during first 2-3mins after
EPOC slow component
after 2mins and persists for up to an hour
EPOC extra slow component
several hours before basal level returns
reasons for EPOC fast component
resynthesis of ATP and PCr
o2 levels restored to myoglobin and haemoglobin
thermogenic effects of hormones
reasons for slow EPOC component
re synthesis lactate to glycogen
thermogenic effects of elevated core temp
HR and VE remain elevated for several mins after
