S1 Lecture 3 Flashcards
(24 cards)
Why do we measure energy expenditure?
- Metabolic needs
- Recovery
- Proportion of energy consumption of each substrate
- Assessment of economy
- Insight into exercise demand
What is the role of RER in estimating energy expenditure?
RER helps estimate the proportion of different substrates utilized for energy during exercise.
Define a calorie.
A unit of heat; the energy required to raise the temperature of 1g of water by 1 Degrees Celsius.
What are the pros of Direct Calorimetry?
- Direct measure of heat
- Accurate for steady state measures
What are the cons of Direct Calorimetry?
- Expensive
- Slow to generate results
- Few in operation
- Limited to accurate exercise measures
What is the RER for 1 molecule of glucose?
1.0
What is the chemical equation for the metabolism of glucose?
6O2 – C6H12O6 -> 6CO2 + 6H2O + 32ATP
What is the RER for 1 molecule of palmitic acid?
0.70
What is the chemical equation for the metabolism of palmitic acid?
23O2 + C16H32O2 -> 16CO2 + 16H2O + 129ATP
List the caloric equivalents for different fuel substrates.
- Fats: 9kcal per g
- Carbs/Protein: 4kcal per g
Which fuel substrate costs the most oxygen per kilocalorie?
Fats
What assumptions does Indirect Calorimetry make?
- Body’s O2 content constant
- CO2 exchange in lung proportional to release from cells
- Little contribution from protein during exercise
What are the limitations of Indirect Calorimetry?
- CO2 released in the lung may not reflect CO2 from working cells
- Protein can contribute up to 5% of total energy in prolonged exercise
- RER values >1 may not provide valid estimations
What is Basal Metabolic Rate (BMR)?
The rate of energy expenditure at rest, decreasing by 2-3% per decade.
What factors can alter Resting Metabolic Rate?
- Change in body composition
- Physical activity
Define MET.
MET = multiples of RMR; 1 MET = 3.5ml/kg/min
How to calculate MET for an activity?
Activity MET = VO2 (ml/kg/min) / 3.5
What is Fat Max?
The exercise intensity at which maximal fat oxidation is observed.
What is the relationship between exercise intensity and substrate use?
Higher intensities favor carbohydrate use, while lower intensities utilize more fat.
What is Excess Post Exercise Oxygen Consumption (EPOC)?
The increased oxygen consumption after exercise to refuel cells and restore energy.
What is Mechanical Efficiency?
Defined as (external work accomplished) / (energy expenditure)
What are average values for mechanical efficiency in cycling, running, and walking?
- Cycling: 20-25%
- Running: 20-25%
- Walking: 20-25%
What is the relationship between VO2max and performance?
Not evident in homogenous groups, but there is a relationship between running economy and performance.
What is the significance of RER?
Describes the ratio between CO2 produced and O2 consumed, indicating substrate contribution.
