Calorimetry and Exercise Metabolism Flashcards
How do you determine amount of energy expended?
- Measure amount of heat produced = direct calorimetry
2. Measure amount of oxygen consumed = indirect calorimetry
What type of exercise burns more fat?
low intensity aerobic exercise
Why is VO2 used?
index of energy expenditure
Factors: Lung, Cardiac Output, Tissues (extraction of O2), Miochondria (ETC) –> Lowest pO2 (gradient)
Indirect Calorimetry
Not measuring VO2 directly
- Measuring Volume of ventilation and Concentration/Expired Gas (O2 and CO2 fractions)
- Looking at input volume – output volume
a. Input: Volume inspired x Fraction of inspired oxygen (21% in normal air)
b. Output: Volume expired x fraction of expired oxygen
Metabolic Equivalent (MET)
One MET Is equal to resting V02
Resting VO2 = 3.5ml/kg/min
Example: 10 MET exercise = 3.5ml/kg/min x 10 = 35
Metabolic Rate
Rate at which body uses energy
Typical range 1200-2400 kcal/ day
Basal Metabolic Rate (BMR)
More experimental
- Increase in muscle mass (1lb gain in FFM: increase of 7-10 kcal/day)
- Increased in body surface area increases metabolic rate because disappating more heat (so metabolism increases to maintain internal body heat)
- Age (2-3% decrease/decade) probably due to loss in muscle mass
- Body Temp (increase in metabolic rate when out of homeostasis range)
- Stress (increase stress = increase rate)
- Diet-induced thermogensis (decreases fasting BMR)
What happens to VO2 max with training?
Increases ergo can do work for longer period of time
What influences VO2 max?
Cardiorespiratory systems ability to deliver oxygen to the muscles
Muscles ability to take up the oxygen and produce ATP aerobically
Oxygen Deficit
When energy is coming from anaerobic sources until aerobic sources can catch up.
This is why running for the first couple of minutes is so hard
What does training do to oxygen deficit?
Decreases it because the body can access the ETC/ Oxidative phosphorylation faster
What does PCr do during exercise?
It is the first pathway to respond during exercise
It initially declines b/c it’s being used and then increases during exercise
What does glycolysis do during exercise?
Initially increases and then it tappers off when ETC has caught up
What happens to VO2 when exercise stops?
Excess Post-exercise Oxygen Consumption = EPOC
VO2 stays elevated
Rapid component to decrease it to a certain point and then have slow component that causes it to remain elevated for >30 minutes
Why is metabolism still elevated after exercise?
Oxygen debt or excess post-exercise oxygen consumption
What contributes to the rapid component of decreasing VO2 after exercise?
- Resynthesis of PCr in muscle
- Restoration of muscle and blood oxygen stores
- Post-exercise elevation of HR and breathing
What contributes to the slow component of decreasing VO2 after exercise?
- Lactate conversion to glucose
- Elevated Body temperature
- Elevated Hormones - SLOWEST
What happens when glycolysis exceeds the rate of oxidative phosphorylation?
Produce lactate
Occurs due to pyruvate backing up into the mitochondria
Lactate Threshold
Point when blood lactate starts to accumulate over resting levels
PH decreases, casues increase in ventilation to remove more CO2
Contributing factors to the Lactate Threshold
- Low muscle oxygen
- Accelerated Glycolysis
- Recruitement of fast twitch fibers
- Reduced rate of oxidative phosphorylation (lactate removal)
How can lactate be used as fuel?
Transported to the liver –> gluconeogenesis converts lactate to glucose –> put in the blood stream and used by the muscles
Process: Lactic acid –> pyruvic acid –> Glucose 6 phosphate –> glucose to the blood
Where else can lactate be metabolized?
- Heart: Uses lactate directly as a fuel
- Type 1 Fibers: remove/burn lactate
- Transported to liver for gluconeogensis (cori cycle)
- Occurs almost as glycosis in reverse
Cori Cycle
Process in which lactate in the blood is transferred to the liver and turned into glucose/glycogen
How does the body remove lactate after exercise?
- 70% converted to pyruvic acid and used by heart + skeletal muscle to make ATP
- 20% is converted to glucose by liver (cori cycle)
- Post exercise, lactate removal faster when light exercise is performed b/c keeps oxidative phosphorylation going
What is the bodies response to increased lactate?
- Decreases pH and buffer it with bicarbonate. This causes more CO2.
- Central chemoreceptors recognize the increase in co2
- Increase ventilation in order to get rid of cO2 (increase pH)
What is the ventilatory response to lactate? aka arterial and venous pressure to oxygen and carbon dioxide
Increases as exercise increases:
- PAO2 (arterial) increases as exercise intensity increases
- Arterial pH decreases as exercise increases
- PaCO2 (arterial) decreases as exercise intensity increases
- PvO2 decreases
- PvCO2 increases
- These venous values reflect what is happening at the tissue –> increase gradient for oxygen and cO2 exchange
- PaO2 stays the same due to 100% saturation
Ventilatory response during submaximal (steady state) exercise?
Ventilatory equivalent = ventilation and metabolism are well matched
25L air/ L oxygen = 50% VO2max
Ventilatory response during severe to max exercise?
Reach ventilatory threshold where ventilation is driven more by tidal volume and frequency of breaths
What do frequency of breaths and tidal volume do during exercise?
Initially tidal volume changes and eventually the body starts to hyperventilate (in a way) to increase frequency of breaths
