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Questions and Answers
Which form of biological work is primarily involved in muscle contraction?
Which form of biological work is primarily involved in muscle contraction?
What is the primary energy currency of the cell?
What is the primary energy currency of the cell?
What happens to ATP levels in skeletal muscle during extreme exercise conditions?
What happens to ATP levels in skeletal muscle during extreme exercise conditions?
Which energy system primarily uses glucose as a substrate?
Which energy system primarily uses glucose as a substrate?
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Under normal resting conditions, how much ATP does the body store?
Under normal resting conditions, how much ATP does the body store?
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Which component of the Metabolic Cart differentiates it from the Douglas Bag Technique?
Which component of the Metabolic Cart differentiates it from the Douglas Bag Technique?
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What impact does an increase in body mass have on energy expenditure during weight-bearing exercises?
What impact does an increase in body mass have on energy expenditure during weight-bearing exercises?
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What is the relationship between anaerobic contribution and oxygen debt during exercise?
What is the relationship between anaerobic contribution and oxygen debt during exercise?
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How can energy cost be expressed to allow for a fair comparison between individuals?
How can energy cost be expressed to allow for a fair comparison between individuals?
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Which factor is likely to decrease the influence of body mass on energy cost when engaging in weight-supported exercise?
Which factor is likely to decrease the influence of body mass on energy cost when engaging in weight-supported exercise?
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What is the primary purpose of indirect calorimetry in measuring energy use?
What is the primary purpose of indirect calorimetry in measuring energy use?
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Which component of Total Daily Energy Expenditure (TDEE) accounts for the highest percentage?
Which component of Total Daily Energy Expenditure (TDEE) accounts for the highest percentage?
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Which method used to measure energy expenditure is the most expensive?
Which method used to measure energy expenditure is the most expensive?
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In measuring respiratory gas exchange, what does the Douglas Bag technique primarily measure?
In measuring respiratory gas exchange, what does the Douglas Bag technique primarily measure?
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How is energy expenditure calculated using the doubly labeled water method?
How is energy expenditure calculated using the doubly labeled water method?
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Study Notes
Measuring Energy Use in Humans
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Total Daily Energy Expenditure (TDEE) is comprised of three main components:
- Physical Activity (15-30%)
- Dietary Induced Thermogenesis (~10%)
- Resting Metabolic Rate (~60-75%)
- Lean muscle mass plays a crucial role in TDEE
Methods Used to Measure Energy Use In Humans
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Indirect Calorimetry: Measures respiratory gas exchange (Oxygen consumed and carbon dioxide produced)
- Open circuit and closed-circuit spirometry two types of indirect calorimetry
- Douglas Bag Technique: Collects expired air, measures volume and fraction of oxygen and carbon dioxide, then calculates VO2 and VE.
- Metabolic Cart: Modernized version of the Douglas Bag Technique using a pneumotachometer, mixing chamber, continuous sampling, and automation.
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Doubly Labeled Water: Isotope-based method used for free-living individuals.
- Participants consume water containing labeled H2 and O2, collects all their excreted urine & saliva, then calculates the difference between elimination rates to determine energy use and excretion.
Energy Use During Different Activities
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Rowing, running, and cycling (2 km) have high energy costs
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Swimming (2 miles/hour) and running (5 miles/hour) have different energy costs; factors like body mass, stroke rate, and water resistance are considerations.
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Influence of Body Mass: Larger body mass increases energy expenditure, especially in weight-bearing exercise.
- Weight-supported exercise (stationary cycling) has a reduced influence of body mass.
Biological Work in Humans
- Three forms of biological work (energy consuming processes):
- Chemical: Biosynthesis
- Mechanical: Muscle contraction
- Transport: Transfer of substances between cells
1st Law of Thermodynamics
- Energy can be transformed from one form to another but cannot be created or destroyed.
ATP (Adenosine Triphosphate): The Cell’s Energy Currency
- Composed of adenosine linked to three phosphates.
- ATPase catalyzes the reaction of ATP with water to form ADP (Adenosine Diphosphate).
ATP: A Limited Currency
- Cells only store a small amount of ATP and must continually resynthesize it.
- ATP levels decrease significantly in skeletal muscle only under extreme exercise conditions.
- The body stores 80-100 g of ATP under normal resting conditions, enough for 2-3 seconds of maximal exercise.
Energy Systems: Metabolic Pathways to Regenerate ATP
- Four main energy systems regenerate ATP:
- Phosphagen System (ATP-CP)
- Anaerobic Glycolysis (glucose/CHO)
- Aerobic System (CHO)
- Lipid (fat)
The Body’s Energy Sources
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Carbohydrate stores:
- Muscle glycogen ~300 g
- Liver glycogen ~100 g
- Blood glucose ~ 10 g (essential for CNS)
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Lipid stores:
- Total store ~10,000 g (average 67 kg person at 15% body fat)
- Significantly more energy per gram of lipid than CHO.
- Total store ~10,000 g (average 67 kg person at 15% body fat)
Respiratory Exchange Ratio (RER)
- Estimate of the Respiratory Quotient (RQ) which is the ratio of CO2 produced to O2 consumed.
- Indicates which fuel is predominantly being used during exercise.
- RER values:
- Fat ~ 0.7
- Carbohydrate ~ 1.0
- Assumes negligible protein use.
Fat Dynamics During Exercise
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Light-to-moderate-intensity exercise:
- Fatty acids provide the predominant energy source in light intensity exercise.
- Energy derives from equal amounts of carbohydrate and fat in moderate intensity exercise.
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Description
This quiz explores the various methods used to measure energy expenditure in humans, focusing on Total Daily Energy Expenditure (TDEE) and the significance of lean muscle mass. It covers techniques like indirect calorimetry and doubly labeled water, providing insight into both laboratory and free-living conditions.
