Calorimetry Flashcards
All metabolic processes result in
Heat production
Rate of heat production reflects
Rate of energy expenditure
Basic unit of heat measurement
calorie
Direct Calorimetry
Measuring heat directly
Indirect Calorimetry
Calculates O2 consumption and CO2 produced to determine how much break down you are engaging in
To convert amount of O2 consumed into heat equivalents depends on
Type of nutrient
about 5kcal of energy is liberated for each L of oxygen consumed
If have VO2 of 2L of oxygen per minute
5 x 2 = 10 kcal/min for energy expenditure
If you worked out for 10 minutes at the level, would burn 100 calories
What is indirect calorimetry measuring
Volume of expired oxygen
Fraction of expired gases
And then from here you calculate VO2 and VCO2 and then can calculate RER (VCO2/VO2) and can figure out what you are burning
Fraction of expired oxygen
about 16%
What is RER for 50/50 of carbs and fat burning
0.85
MET
Metabolic Equivalent
One MET =
Resting VO2
About 3.5 ml/kg of body mass/min
Energy cost of exercise can be described based on
Multiples of resting VO2
VO2 for 10 MET exercise
3.5 x 10 = 35 mL/kg/min
Light exercise is how many MET
2.5 to 5 METS
4 is usually good for patients
Metabolic Rate
Rate at which the body uses energy
Basal Metabolic Rate
More of a lab setting
BMR influenced by
Inc in muscle mass Inc in body surface area (thermoregulation) Dec in age Inc body temp Inc stress Inc diet induced thermogenesis
Oxygen uptake ____ until ____
Oxygen uptake increases linearly until VO2 max is reached
Trained versus untrained with oxygen uptake
Untrained will plateau at an earlier state (VO2 max is lower)
Factors influencing VO2 max
CO
AVO2 Max
What is happening at rest
almost 100% of ATP is produced by aerobic metabolism
Blood lactate is low because are producing but getting rid of it just as fast
VO2 = 0.25L/min
Transition to Exercise (from sitting)
Your muscles require energy immediately - ATP PCr provides until VO2 can catch up (until ETC can get there)
Repesents oxygen deficit
Oxygen deficit with training
Decreases
You can get to steady state VO2 faster
Order for sitting to exercise
PCr (Anaerobic)
Glycolysis (Anaerobic)
ETC - VO2 catches up (Aerobic)
After you stop exercising what happens?
EPOC - Excess Post Exercise Oxygen Consumption
You grow the deficit the more intense the exercise you start with is
EPOC can happen for up to an hour or more
Why is metabolism still elevated after exercise
You are trying to reform stores of fuel and resynthesize and get all back to normal
Fast portion - 1 to 3 minutes
Slow portion - more than 30 minutes (elevated hormones and body temp)
If you inc rate of glyclosis more than ETC can handle
Pyruvate will get converted to lactic acid –> LDH important in this
Fast twitch muscle fibers favor this lactic acid formation
Onset of Blood Lactate Accumulation
4mmol/L
Contributing factors to lactate in blood
Low muscle oxygen
Accelerated glycolysis
Recruitment of fast twitch fibers
Reduced rate of lactate removal
Lactate Threshold - Untrained
50-60%
Lactate Threshold - Trained
70-90%
Will be at higher intensity before start to form lactate
Removal of lactate during exercise
Up to 40% produced in muscle is metabolized elsewhere
Heart (70%)
Type 1 fibers
Liver - to produce glucose 6 phosphate (20%)
Removal of Lactate following exercise
If do nothing - takes longer to get rid of lactate
Light exercise - reduces this time
When you reach the lactate threshold what is happening to ventilation
It is increasing
Inc lactate –> inc acidity of blood –> more bicarb –> more CO2 –> hyperventilate
Ventilatory Threshold
When ventilation exceeds oxygen uptake
Thresholds represent
Point where your production has exceeded removal and this leads to increase in ventilation
