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
Describe the oxygen deficit?
- the difference between total oxygen consumed and total that would be consumed with immediate steady-rate uptake
What does the Oxygen Deficit represent?
- immediate anaerobic energy transfer from the hydrolysis of intramuscular high-energy phosphates and glycolysis until steady-rate energy transfer meets current energy demands
How does the energy for exercise occur?
- smooth blending and considerable overlap of different modes of energy systems
What is the oxygen uptake fast component?
- Exponential rise in oxygen uptake in first minutes of physical activity
- reaches a plateau after at around 3rd or 4th minute
What is unique about endurance-trained individuals regarding steady-rate?
Compared to sprint-power athletes, cardiac patients, older adults, and untrained:
- Reach it more rapidly
- Smaller oxygen deficit
What causes a trained individual to consume a greater total amount of oxygen during steady-rate exercise? What else does it do?
Faster Aerobic Kinetic Response
- makes an anaerobic component of exercise energy transfer proportionally smaller
What three aerobic training adaptations facilitate the rate of aerobic metabolism when exercise begins?
- Rapid increases in muscle bioenergetics
- Rapid Increase in overall blood flow
- Disproportionally larger regional blood flow to active muscle, complimented by cellular adaptations
What do the three aerobic training adaptations that facilitate the rate of aerobic metabolism when exercise begins do?
- Increase individual total capacity to generate ATP aerobically
when does VO2max occur?
when oxygen uptake plateaus or increases only slightly with additional exercise intensity
What does a High VO2max require?
Integration and high-level responses of:
1. Pulmonary Ventilation
2. Hemoglobin Concentration
3. Blood Volume and Cardiac Output
4. Peripheral Blood Flow
5. Aerobic Metabolism
What are the four factors that Hill suggests determine VO2max?
- Arterial O2 Saturation
- Mixed Venous Saturation
- O2 capacity of the Blood
- Circulation Rate
What quantitative estimate is made for arterial O2 saturation?
- Ventilation
Hill noticed no cyanosis, and assumed that the lungs oxygenated the blood well enough
What quantitative estimate is made for Mixed Venous Saturation?
- Central Blood Flow
What quantitative estimate is made for O2 capacity of the blood?
- Active Muscle Metabolism
Which quantitative estimate is made for the circulation rate?
- Peripheral Blood Flow
Why are athletics used for study on exercise physiology?
- Simple, measurable, and constant
- Athletes: reduced danger (healthy)
- Exciting and new for physiology (more recruits)
Why are both muscle twitch fibers usually required for most sports?
- slow, sustained muscle action
- Short bursts of power
What do athletes who excel in different sports usually have with regard to muscle fiber type?
- a large percentage of specific muscle fiber type that supports that sport’s energy demand
Describe Fast-Twitch Muscle Fibers
Type II
- Rapid Contraction Speed
- High Capacity for Anaerobic ATP production
Type IIa
- High Aerobic Capacity
Describe Slow-twitch muscle fibers
- Generate energy through aerobic pathways
- Slow contraction speed
What type and percentage of muscle fibers would a swim champion have?
Type II
- Fast-twitch
- 80%
What type and percentage of muscle fibers would an endurance cyclist have?
Type I
- Slow-twitch
- 80%
What is EPOC?
Excess Post-exercise Oxygen Consumption
Which 7 things contribute to EPOC?
- Resynthesize ATP & PCr
- Resynthesize Lactate to Glycogen
- Oxidize Lactate for energy metabolism
- Restore Oxygen to Myoglobin and Blood
- Restore thermogenic effects of elevated core temp
- Thermogenic effect of hormones (catecholamines)
- Restore Elevated HR, VE, other physio function
What happens during recovery from steady-state exercise?
- Re-synthesis of high-energy phosphates
- replenish O2 in blood
- Replenish bodily fluids
- replenish muscle myoglobin
- small energy cost to elevate circulation/ventilation
Why is passive procedure important during recovery from steady state exercise?
- additional exercise elevates total metabolism, delay recovery
What do most individuals do when left to their own choice regarding recovery from steady-state exercise?
- Select optimal recovery intensity
What does performing aerobic exercise in recovery do to lactate?
- Accelerates blood lactate removal
Why does performing aerobic exercise in recovery from non-steady state exercise accelerate blood lactate removal?
Increased
- blood perfusion through the liver, heart, and ventilatory muscles
- blood flow through skeletal muscles in active recovery
Describe Intermittent Interval Physical Activity
- Supramaximal exercise to overload specific energy transfer system
- Rapid recovery in interval
What can you do in interval training to overload a specific energy-transfer system?
- Manipulate duration of exercise and rest intervals
define blood lactate threshold
when muscle cells can
neither meet energy demands aerobically nor oxidize lactate at its rate of formation
what affects blood lactate independent of oxygen consumption
muscle fiber type used
what kind of information does VO2max provide?
- It provides a quantitative measure of a person’s capacity for sustained aerobic ATP re-synthesis
- Indicates ability to maintain intense exercise for longer
than 4 to 5 minutes
describe type 1 muscle fibers
- Generates energy through aerobic pathways.
- Slower contraction speed than fast-twitch fibers.
- Active in continuous activities requiring steady-rate aerobic
energy transfer
define lactate threshold
when muscle cells can neither meet energy demands aerobically nor oxidize lactate at its rate of formation
