energy expenditure

Question 1

what is the 1st law of thermodynamics

Answer 1

energy is not created or destroyed, it is transferred

Question 2

what is an endergonic reaction

Answer 2

chem reaction stores energy
anabolism - building block precursors (food) to synthesised end products (macros)
- needs ATP (converting food to macros)

Question 3

what is an exergonic reaction

Answer 3

physical or chem processes that release energy (downhill)
catabolism - CHO, fats, proteins + O2 to H2O and CO2
- resynthesises ATP (produces energy)

Question 4

what is the 2nd law of thermodynamics

Answer 4

spontaneous transfer of PE decreases the capacity to perform work
- PE degrades to KE

Question 5

what are the 3 forms of biological work done in humans

Answer 5

mechanical (muscle contraction)
chemical (hypertrophy)
transport (diffusion vs active)

Question 6

what is phosphorylative coupling efficiency

Answer 6

proportion of PE retained as ATP is synthesised
endergonic reaction

Question 7

what is mechanical coupling efficiency

Answer 7

proportion of total chem energy that contributes to external work
- amount of ATP that gets converted to mech work

Question 8

what is the % efficency of humans

Answer 8

phosphorylative ~60%
mechanical ~ 50% (50% of the 60%)
overall efficiency = 30%

Question 9

what is direct calorimetry

Answer 9

sealed chamber to measure heat production from metabolic processes
- can calculate energy released based on temp changes
(gold standard but not accessible)

Question 10

what is indirect calorimetry

Answer 10

measures O2 consumption as an estimate of energy expenditure
5 kcal/L O2 consumed
all energy reactions ultimately depend on O2 use

Question 11

what is the difference between open and closed calorimetry

Answer 11

open = used for real word scenarios (HIIT, etc), measures throughout the task
closed = only measure at the end of the task, limited to steady state aerobic activities where energy production is completely produced using O2 (or at rest)

Question 12

what is 1 MET

Answer 12

resting O2 consumption
= 3.5 mL/kg/min
- way of standardising exercise intensity

Question 13

what are the three main components of total daily energy expenditure (TDEE)

Answer 13

thermic effect of feeding (10%)
RMR (60-75%)
thermic effect of PA (15-30%)

Question 14

what is obligatory thermogenesis

Answer 14

digesting and processing food
growth
pregnancy
(not under your control)

Question 15

what is facultative thermogenesis

Answer 15

on top of obligatory depending on environmental condition
control of thermoregulation
(ex: shivering vs sweating to maintain temp)

Question 16

what is basal metabolic rate (BMR)

Answer 16

minimum amount of energy needed to sustain vital function in the waking state
0.8-1.4 kcal/min
(stringent test conditions make it impractical)

Question 17

what are the factors affecting RMR

Answer 17

body surface area
- same body size = same RMR

sex
- strong association between fat free mass and RMR (usually higher in men)

age
- RMR declines with age (product of fat free mas delcining)
- highest around 2-3yo

Question 18

how do you measure RMR

Answer 18

avoid PA before or during
in postabsorptive state (fasting 4-5 hours after meal - glucose released from liver to keep blood glucose up)