Chapter 7 - Energy Transfer During Physical Activity Flashcards
What is the ATP-PCr Energy System Responsible for?
High-Intensity Exercise of Short Duration
- Under 10 seconds
How much ATP and PCr does each kg of skeletal muscle contain?
ATP
- 3-8mmol
PCr
- 12-48mmol
What is the Short-term Glycolytic Energy System responsible for?
Intense, Short-duration exercise
What results from short-term glycolytic energy systems?
- lactate formation
When would there be rapid and large accumulation of blood lactate?
Maximal Exercise of 60-180 seconds
What happens when you decrease intensity of exercise to extend duration?
- Depressed lactate accumulation rate
- Reduced final blood lactate levels
Does blood lactate accumulate at all exercise levels?
- NO
When does blood lactate not accumulate during exercise?
Light/Moderate Exercise
- Under 50% aerobic capacity
Why does blood lactate not accumulate during light/moderate exercise?
- Lactate production equals lactate clearance
- Oxygen-consuming reactions adequately meeting exercise energy demands
What have tracer studies that label the carbon in glucose show about lactate?
- 70% oxidizes
- 20% converts to glucose in muscle/liver
- 10% synthesizes amino acids
Why would a trained person perform steady-rate aerobic exercise at 80-90% of maximum aerobic capacity?
- Specific Genetic Endowment
- Specific local training adaptations that favour less lactate production
- More rapid rate of lactate removal at any exercise intensity
What is the difference between lactate concentration for trained and untrained individuals?
Untrained
- Early lactate threshold
- Lower max lactate tolerance
Trained
- Steep curve
- Later lactate threshold
- High tolerance
Which factors are related to the lactate threshold?
- Low tissue oxygen
- Reliance on Glycolysis
- Activate fast-twitch muscle fibers
- Reduced lactate removal
What factors contribute to higher blood lactate levels during maximal exercise due to specific sprint-power anaerobic training? Are these factors permanent?
Factors
- Improved motivation
- Increased intramuscular glycogen stores
- Increase in Glycolytic-Related Enzymes
-not permanent and decreases when training ceases
What does lactate shuttling between cells do?
- enables glycogenolysis in one cell to supply other cells with fuel for oxidation
Other than lactate production, what is the muscle also a major site for?
- Removal of lactate via oxidation
What happens to glucose that is derived from lactate?
- Returns in blood to skeletal muscle for energy metabolism
- Synthesizes to glycogen for storage
What is the long-term energy system?
- The Aerobic System
When does aerobic metabolism provide nearly all the energy transfer
when intense exercise continues beyond several minutes
What happens with oxygen uptake during exercise?
Initially
- Rises exponentially
Eventually
- Plateaus, then remains in steady-rate for duration of effort
Explain steady-rate aerobic metabolism
- balance between energy required and ATP production in aerobic reactions
What happens to lactate during steady-rate conditions?
- No appreciable blood lactate accumulation
Steady-rate aerobic metabolism could progress indefinitely. However, what 2 factors limit how long you can sustain steady-rate metabolism?
- fluid loss/electrolyte depletion
- depletion of glycogen reserves in liver for CNS and muscle to power exercise
flagged for redundancy
What two factors help explain athlete’s high steady-rate levels?
- High capacity for oxygen delivery to working muscles (central circulation)
- High capacity of active muscles to use oxygen