Energy Expenditure During Rest and Physical Activity

Question 1

RMR vs. BMR

Answer 1

BMR:

• Basal metabolic rate
• Rate of energy expenditure at rest
• In supine position
• Thermoneutral environment
• After 8-12 hours of fasting

RMR:

• Resting metabolic rate
• Within 5-10% of BMR but easier to assess
• Doesn’t require stringent standardized conditions

Question 2

Factors affecting TDEE

Answer 2

• Resting metabolic rate
• Thermogenic influence of consumed food
• Energy expended during physical activity and recovery

Question 3

Direct vs. Indirect calorimetry

Answer 3

• Direct calorimetry measures heat, is more expensive, slow to generate results, good for resting metabolic measurements, done in an airtight chamber with copper tubing in the walls
• Indirect is newer, estimates total body energy expenditure based on O2 used and CO2 produced, measures respiratory gas concentrations and accurate for steady-state aerobic activity

Question 4

VCO2 equation

Answer 4

Volume of expired CO2 minus volume of inspired CO2

Question 5

VO2 equation

Answer 5

Volume of inspired O2 minus volume of expired O2

Question 6

RER (respiratory exchange rate) equation

Answer 6

VCO2 divided by VO2

Question 7

What does MET stand for and what are some resting values?

Answer 7

• Metabolic equivalent of task
• Provides a convenient way to rate exercise intensity from a resting baseline
• The average MET for an adult in a seated resting position is one

Question 8

Factors influencing efficiency of movement and how walking and running economy can be affected

Answer 8

Factors:

• Work rate
• Movement speed
• Extrinsic factors
• Muscle fiber composition
• Fitness level
• Body composition
• Technique
• A linear relationship exists between walking speeds of 3.0-3.5kmh and oxygen uptake
• At faster speeds, walking becomes less economical so the relationship curves upward to indicate a disproportionate increase in energy cost related to walking speed
• Crossover velocity is 4mph where running becomes more economical than walking

Question 9

Factors affecting VO2max

Answer 9

Exercise mode
- Reflect the quantity of activated muscle mass

Heredity:
- Current estimates ascribe 30% for VO2max, 50% for HR max

Training state:
- Aerobic capacity with training improves 6-20%; largest improvement occurs among the most sedentary individuals

Gender:
- VO2max for women is 15-30% below men

Body composition:
- Differences in body mass explain roughly 70% of the differences in VO2 max

Age:
- Older = lower VO2max

Question 10

Know limitations between VO2max predictions and HR predictions

Answer 10

• Linearity of HR-VO2 relationship
• Similar max HR’s for all subjects
• Assumed constant exercise economy
• Day-to-day variation in exercise HR

Question 11

EPOC

Answer 11

• Excess Post Exercise Oxygen Consumption
• Body incurs O2 deficit
• Attempts to maintain homeostasis
• Occurs when the demand for oxygen exceeds the amount of consumed oxygen during exercise
• Replenish ATP/PCr stores;
• Replenishes hemoglobin/myoglobin;
• Converts lactate to glycogen;
• Clears CO2

Question 12

Lactate threshold

Answer 12

• Point at which blood lactate accumulation increases markedly
• Lactate production rate is greater than lactate clearance rate
• Interaction between aerobic and anaerobic systems
• Expressed as a percentage of VO2max
• AKA OBLA
• Lactate accumulation leads to fatigue
• Higher threshold = higher sustained exercise intensity and better endurance performance