Lecture 3 (Exam 2) Flashcards
Direct Calorimetry
Measures the body’s heat production to calculate energy expenditure & ~60% of energy produced is released as heat
-Expensive process and cannot follow rapid changes in energy release
Indirect Calorimetry
Estimates total body energy expenditure based on RER of VO2 used, VCO2 produced
- Heat production is not measured here
- Only accurate for steady-state oxidative metabolism
Maximal Oxygen Uptake (VO2max)
Point at which O2 consumption doesn’t increase with further increase in intensity
- Best single measurement of aerobic fitness
- Not best predictor of endurance performance
- Plateaus after 8 to 12 weeks of training
- More training allows athlete to compete at higher percentage of VO2max
Basal Metabolic Rate (BMR)
Measurement takes place while the subject rests, no food within the past 12 hours, no physical activity within 2 hr
-the lowest amount of energy needed to maintain normal regulatory balance (about 1200 – 2400 kcal per 24hr)
Resting Metabolic Rate (RMR)
RMR = 60 – 75% of total daily energy expenditure
Steady State
Refers to the energy cost (VO2) at a specific power output
Peak Oxygen Uptake (VO2peak)
point of volitional fatigue before VO2max is “truly” reached
Absolute VO2max
expressed in an absolute value of LO2/min
-Untrained young men: 44 to 50 versus Untrained young women: 38 to 42
Relative VO2max
expressed in a relative value (i.e., body weight) of ml O2 kg-1/min-1
- allows for a more accurate comparison of VO2max for different-sized individuals
- Untrained young men: 44 to 50 versus Untrained young women: 38 to 42
Excess Postexercise Oxygen Consumption (EPOC)
Volume of O2 consumed during the minutes immediately after exercise ceases that is above that normally consumed at rest
-O2 consumed > O2 demanded amount in early recovery
Oxygen Deficit
O2 needs and O2 supply differ from transition of rest to exercise
-O2 demand > O2 consumed in early exercise OR O2 required − O2 consumed
Occurs when anaerobic pathways used for ATP production
Lactate Threshold
point at which blood lactate accumulation increases significantly
-Lactate production rate > lactate clearance rate
-Interaction of aerobic and anaerobic systems
-Good indicator of potential for endurance exercise
Resting lactate levels are ~ 0.8-1.5 mmol/L
Lactate and Performance
expressed as a percentage of VO2max is one of the best determinants of endurance performance
- Untrained people: LT of 50 – 60 % of VO2max
- Trained: LT 70 – 80 % of VO2max
Respiratory Exchange Ratio (RER)
The ratio between CO2 released (VCO2) and oxygen consumed (VO2)
-can be used to determine energy substrate used at rest and during exercise with a value of 1.00 indicating CHO and 0.70 indicating fat
-Each liter of oxygen consumed generates ~ 5 kcal of energy
-Predicts substrate use, kilocalories / O2 efficiency
Equation RER = VCO2/VO2
3 components of Total Daily Energy Expenditure (TDEE) and their % contributions to TDEE
Physical Activity - 15-30%
Thermogenesis effect from eating - 10%
RMR - 60-75%
5 Factors Affecting Basal Metabolic Rate (BMR)
Mass: The more fat free mass the ↑ BMR
Body Surface: ↑ body surface area for more heat loss ↑ BMR
Age: BMR ↓ with ↑ age, generally due to loss of FFM
Stress: ↑ stress ↑ activity of SNS which ↑ BMR
Temperature: BMR ↑ with ↑ temperature
4 Factor Effecting Daily Energy Expenditure (DEE)
Physical Activity
Diet-Induced Thermogenesis (from eating)
Climate
Pregnancy
Normal Values of BMR
1200 - 2400 kcal/24hr
5 Causes of Fatigue
Phosphocreatine depletion Glycogen depletion -"hitting a wall" during a 400m Lactic acid accumulates during brief, high-intensity exercise Neuromuscular Fatigue Stress and psychological factors
4 Criteria for VOmax Attainment
Demonstration of leveling off in VO2
Attainment of age-predicted max heart rate
RER > 1.10
RPE > 17
Factors Responsible for EPOC
- Rebuilding depleted ATP stores
- Clearing lactate produced by anaerobic metabolism
- Replenishing O2 supplies borrowed from hemoglobin and myoglobin
- Removing CO2 accumulated in body tissues
- Reduce body temperature
- Remove circulating hormones due to increased respiratory rate
Norms for VO2max
Untrained young men: 44 to 50 versus untrained young women: 38 to 42
- TM exercise usually produces highest values with arm crank exercise about 70% of TM
- Swimmers achieve VO2max values about 11% below TM during swimming tests
4 Factors of having Endurance Success
- High V•O2max
- High lactate threshold (as % V•O2max)
- High economy of effort
- High percentage of type I muscle fibers
3 Adaptations in Aerobic Training
- Improved sub-maximal aerobic endurance and VO2max
- Muscular changes in fiber size, blood and oxygen supply
- Changes depend upon genetic factors with upper limits
Aerobic Training
leads to:
- improved blood flow
- Increased capacity of muscle fibers to generate ATP
Muscular Adaptations of Aerobic Training
- Increased size of ST fibers but no change in fiber type. Within fiber type FTx become more FTa (more oxidative)
- Increased number of capillaries supplying the muscles
- Increased myoglobin content of muscle by 75% to 80%
- Increased number, size, and oxidative enzyme activity of mitochondria
