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What is the primary energy system used during endurance exercise, such as long-distance running?
The predominant energy system used during endurance exercise is the oxidative phosphorylation system.
How many ATP can be produced from the metabolism of glucose in skeletal muscle?
30 ATP can be produced from the metabolism of glucose in skeletal muscle.
Which enzyme is considered a rate-limiting enzyme in the oxidative phosphorylation system?
Phosphofructokinase (PFK) is a rate-limiting enzyme in the oxidative phosphorylation system.
What is the effect on fuel utilization with increased exercise intensity?
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What is the potential duration of the oxidative phosphorylation system?
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How many ATP are produced from the metabolism of glycogen in skeletal muscle?
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What are the primary substrates oxidized during oxidative phosphorylation?
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What fatigue is associated with fuel depletion during exercise?
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What is the primary function of creatine phosphate in muscle tissues?
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How is ATP produced from creatine phosphate during high-intensity exercise?
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What duration of exercise predominantly utilizes the creatine phosphate energy system?
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What is the primary energy source during anaerobic glycolysis?
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What is the rate-limiting enzyme in anaerobic glycolysis?
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What chemical change occurs that leads to fatigue during the anaerobic glycolysis process?
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In what situations is the anaerobic glycolysis system primarily utilized?
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How does creatine absorption occur in the body?
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What effect does creatine phosphate depletion have on muscle performance?
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What is the significance of the creatine shuttle in energy metabolism?
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What impact does carbohydrate (CHO) depletion have on Type I muscle fibers?
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How do Type II fibers differ in efficiency compared to Type I fibers during exercise?
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What is the role of dietary nitrate in enhancing exercise performance?
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Explain how beetroot juice can affect the oxygen consumption slow component during exercise.
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What is the effect of increased blood flow on muscle contractions?
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What is the significance of L-arginine in muscle performance?
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How does time to exhaustion relate to beetroot juice consumption in athletes?
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What happens to Type II fibers' recruitment in the presence of adequate dietary nitrate?
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During the fed state, what is the primary use of glucose in the liver?
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What metabolic process primarily occurs in the liver during the postabsorptive state?
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What happens to muscle protein during fasting (18 to 48 hours without food)?
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What is the role of dietary sodium bicarbonate loading in exercise performance?
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How does glucose availability change for the CNS during starvation (>48 hours without food)?
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How does exercise intensity affect substrate utilization during ATP re-synthesis?
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In adipose tissue, how are triglycerides utilized in the postabsorptive state?
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Describe the 'slow component' of oxygen consumption during exercise.
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What is the role of lactate during the fasting state in glucose production?
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What factors influence the presence and extent of the 'slow component' in oxygen consumption?
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What is the primary energy source for muscle during the starvation state?
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What is the relationship between exercise duration and aerobic metabolism?
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What metabolic change occurs in liver glycogen stores during fasting (18 to 48 hours)?
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What determines the metabolic pathways favored by the liver during the fed state?
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How does the muscle adapt to energy needs during different metabolic states?
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Describe one way in which protein intake can support muscle adaptation during strength
training (3 marks)
2. Describe the Australian Institute of Sport’s Supplement Framework (4 marks)
3. Outline 3 dangers in in consuming supplements (3 marks)
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4. Define hypohydration and hyperhydration, and explain how the body loses and gains
water and sodium (4 marks)
5. (a) Describe how muscle glycogen and blood glucose are utilised to fuel exercise at
different intensities (2 marks)
(b) Outline carbohydrate intake recommendations for athletes before, during, and after
exercise, considering both shorter (under 60 minutes) and longer (over 60 minutes)
durations, and explain the importance of these recommendations for performance and
recovery (4 marks)
6. Explain how reducing meat consumption in an athlete's diet can align with both sports
nutrition and environmental sustainability (4 marks)?
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What are the three primary energy systems used to replenish ATP during exercise, and how do they differ in their characteristics?
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Describe the specific role of anaerobic glycolysis in ATP replenishment during high-intensity exercise.
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How does the oxidative phosphorylation system utilize carbohydrates, fats, and proteins for ATP production during prolonged exercise?
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Explain the concept of VO2max and its significance in evaluating an athlete's performance.
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What is the 'oxygen slow component' during exercise, and how does it relate to ATP production?
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What are the main characteristics of the creatine phosphate energy system in ATP replenishment during exercise?
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How does anaerobic glycolysis contribute to ATP replenishment during high-intensity exercise?
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Describe the oxidative phosphorylation energy system and its role in ATP production during prolonged exercise.
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Explain how fuel utilization is measured using the respiratory exchange ratio (RER) during exercise.
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What is the oxygen slow component, and how does it relate to energy systems and maximal work capacity?
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What unique characteristics define the creatine phosphate energy system and its role in ATP replenishment during short-duration, high-intensity exercise?
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In what specific situations is anaerobic glycolysis particularly beneficial for ATP replenishment, and what are its key characteristics?
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Describe the process of oxidative phosphorylation and how it supports ATP replenishment during prolonged exercise.
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How does the concept of VO2max relate to an athlete's performance and oxygen consumption during exercise?
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What is the oxygen slow component and how does it affect energy production during sustained exercise?
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Explain how the respiratory exchange ratio can be used to measure fuel utilization during exercise.
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What factors influence fuel utilization during exercise, particularly concerning different intensities and durations?
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Study Notes
Creatine Phosphate Energy System
- High-energy phosphate compound similar to ATP
- Stored in muscle and other tissues
- May also be referred to as phosphocreatine, PC, PCr, and CP
- Serves as a readily accessible reservoir of energy
- One chemical step
- Anaerobic
- Catalyzed by creatine kinase (CK)
- Very fast reaction
- 1 ATP per CrP molecule
- 10-second duration
- Fatigue associated with CrP depletion
- Predominant energy system in very high intensity exercise
Creatine Metabolism
- Dietary creatine is absorbed in the gut
- Creatine uptake into skeletal muscle
- Utilisation of ATP and Creatine Phosphate during short, high-intensity exercise
Anaerobic Glycolysis System
- 18 chemical steps/reactions: 6 are repeated
- 12 chemical compounds, 11 enzymes
- Anaerobic
- 1- to 2-minute duration
- Fatigue associated with decreased pH (metabolic acidosis)
- Rate-limiting enzyme: phosphofructokinase (PFK)
- Predominant energy system in high-intensity exercise
Oxidative Phosphorylation System
- 124 chemical steps/reactions
- 30 compounds, 27 enzymes
- Potentially limitless duration
- Aerobic
- Fatigue associated with fuel depletion
- Rate-limiting enzymes: phosphofructokinase (PFK), isocitrate dehydrogenase (IDH), and cytochrome oxidase (COX)
- 30 ATP via glucose and 31 ATP via glycogen
- Predominant energy system in endurance exercise
Fuel Utilization
- Substrates and exercise intensity
- Increasing contribution of carbohydrate fuels, notably muscle glycogen, is observed at higher exercise intensities.
Metabolic Pathways
- Liver, muscle, adipose tissue, and central nervous system (CNS) utilize different metabolic pathways depending on the physiological state:
- Fed state: Glucose used for energy, stored as glycogen, and converted to fatty acids.
- Postabsorptive state: Glycogen broken down to provide glucose; lactate and alanine released to liver to make glucose.
- Fasting state: Liver glycogen is depleted; glucose made from lactate and amino acids provided by muscle.
- Starvation state: Liver continues to manufacture glucose, predominantly from glycerol; ketones produced for use by CNS and muscle.
Triglyceride and Fat Oxidation
- High rate of fat oxidation and low level of plasma triglyceride concentration during the postprandial test.
Oxygen Slow Component: Nutrition
- CHO depleted versus CHO restored
- Type I fibres are less efficient in the resynthesis of ATP.
- Evident higher oxygen consumption is also drifting by minutes 15-20.
Oxygen Slow Component: Nutrition
- Dietary nitrate is classed in Group A (performance enhancing)
- Increased nitrate contributes to nitric oxide synthase (NOS) production, which promotes vasodilation.
- L-arginine also stimulates NOS activity.
- Both pathways promote blood flow especially at the commencement of muscle contractions.
Oxygen Slow Component: Nutrition
- Dietary sodium bicarbonate loading is classed in Group A (performance enhancing)
- More time is spent in the rapid component and then there is a blunting of the slow component.
Summary
- Provision of energy is dependent on multiple factors, such as the intensity and duration of the exercise stimulus.
- The intensity of exercise influences the mix of substrates used to fulfill the ATP re-synthesis rate.
- Oxygen consumption is observed to undergo a ‘slow component’ that is influenced by the training status of the individual and most likely underpinned by the muscle fibre type contribution to the exercise.
Rephosphorylation of ATP
- ATP is the body’s primary energy currency, used to power various cellular functions.
- Rephosphorylation refers to the process of adding a phosphate group back to ADP (adenosine diphosphate) to form ATP.
- This process is crucial for replenishing ATP stores during exercise and maintaining energy levels.
Energy Systems
- Three main energy systems contribute to ATP rephosphorylation during exercise:
- Creatine phosphate (CP) system
- Anaerobic glycolysis
- Oxidative phosphorylation (aerobic) system
Creatine Phosphate (CP) System
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Characteristics:
- Fastest energy system, providing ATP for short, intense bursts of activity (e.g., sprinting).
- Utilizes creatine phosphate (CP) stored in muscle cells.
- CP donates a phosphate group to ADP, forming ATP.
- Limited CP stores, lasting only 5-15 seconds.
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Replenishing ATP:
- During high-intensity exercise, CP is broken down to provide a phosphate group to ADP, producing ATP.
- Replenished during rest or low-intensity activity through the use of ATP.
- The CP system is the first line of defense for energy production, providing the initial burst of energy needed for intense activities.
Anaerobic Glycolysis
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Characteristics:
- Provides ATP for moderate-intensity exercise lasting 30 seconds to 2 minutes.
- Does not require oxygen, breaking down glucose to pyruvate.
- Produces ATP and lactic acid as a byproduct.
- Lactic acid accumulation leads to muscle fatigue and soreness.
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Replenishing ATP:
- Glucose is broken down into pyruvate through a series of enzymatic reactions.
- This process yields a net gain of 2 ATP molecules.
- Anaerobic glycolysis becomes the dominant energy system during moderate-intensity exercise when the CP stores are depleted.
Oxidative Phosphorylation (Aerobic) System
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Characteristics:
- Primary energy system for sustained exercise.
- Requires oxygen to produce ATP from carbohydrates, fats, and proteins.
- Occurs in mitochondria, the powerhouses of cells.
- Yields significantly more ATP than anaerobic glycolysis.
- Allows for longer duration of exercise and endurance activities.
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Replenishing ATP:
- Broken down fuels (carbohydrates, fats, proteins) are oxidized within mitochondria.
- This process generates electrons that power a chain of reactions, ultimately producing ATP through the electron transport chain.
- Aerobic metabolism is the primary way the body fuels prolonged activity and replenishes ATP stores.
Aerobic Metabolism of Fuels
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Carbohydrate Metabolism:
- Glucose is the primary fuel source for aerobic metabolism.
- It is broken down via glycolysis, the Krebs cycle, and the electron transport chain, generating ATP.
-
Fat Metabolism:
- Fatty acids are broken down through a process called beta-oxidation, generating acetyl-CoA, which enters the Krebs cycle to produce ATP.
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Protein Metabolism:
- Amino acids can be used as a fuel source, primarily during prolonged exercise or calorie restriction.
- Proteins are broken down into amino acids, which can be converted into glucose or enter the Krebs cycle.
Respiratory Exchange Ratio (RER)
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Concept:
- RER is a measure of the ratio of carbon dioxide produced to oxygen consumed.
- Indicates the proportion of carbohydrates and fats being used as fuel.
- RER of 1.0 indicates that carbohydrates are the primary fuel.
- RER of 0.7 indicates that fats are the primary fuel.
Factors Influencing Fuel Utilization
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Exercise Intensity:
- As intensity increases, the reliance on carbohydrates increases.
- At high intensities, nearly all energy is derived from carbohydrates.
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Exercise duration:
- During prolonged exercise, the body shifts from carbohydrate to fat as a primary fuel source.
- Fat oxidation becomes more prominent as glycogen stores deplete.
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Training status:
- Trained individuals have a greater capacity to utilize fat as a fuel, conserving glycogen stores.
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Diet:
- Dietary intake of carbohydrates and fats influences fuel utilization.
- A high carbohydrate diet will lead to a greater dependence on carbohydrates as a fuel source.
Oxygen Consumption and VO2max
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Oxygen Consumption (VO2):
- The rate at which the body consumes oxygen during exercise.
- Increases linearly with exercise intensity up to a certain point.
- Reaches a plateau known as VO2max, representing the maximum oxygen uptake.
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VO2max:
- Maximum oxygen uptake, representing the body's ability to utilize oxygen during intense physical activity.
- A measure of cardiovascular fitness and aerobic capacity.
- Highly influenced by genetic factors and training.
Oxygen Slow Component
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Concept:
- During prolonged, moderate-intensity exercise, oxygen consumption continues to rise slowly after reaching a steady state.
- This gradual increase is known as the oxygen slow component.
- It is associated with a slow shift from anaerobic to aerobic metabolism, requiring more oxygen for oxidative phosphorylation.
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Impact on Work Capacity:
- The oxygen slow component influences maximal work capacity, particularly during prolonged activities.
- As more oxygen is required for aerobic metabolism, the body can sustain higher workloads for longer periods.
- This highlights the importance of aerobic training for improving endurance and work capacity over time.
Rephosphorylation of ATP
- ATP is the primary energy source for muscle contraction
- Rephosphorylation is the process of adding a phosphate group to ADP to create ATP
- There are three main energy systems for rephosphorylation:
- Creatine phosphate system
- Anaerobic glycolysis system
- Oxidative phosphorylation system
Creatine Phosphate Energy System
- Provides ATP for short bursts of high-intensity activity
- Uses creatine phosphate (CP) to donate a phosphate group to ADP
- Limited by the amount of CP stored in the muscle
- Lasts around 10-15 seconds
- Important for activities like sprinting, weightlifting, and jumping
Anaerobic Glycolysis Energy System
- Provides ATP for moderate-intensity activities lasting longer than the creatine phosphate system
- Breaks down glucose without oxygen into pyruvate
- Produces lactic acid as a byproduct which can limit the system
- Lasts around 2-3 minutes
- Important for activities like soccer, basketball, and swimming sprints
Oxidative Phosphorylation Energy System
- Provides ATP for long-duration, low-intensity activities
- Uses oxygen to break down fuels like carbohydrates, fats, and proteins
- Most efficient energy system, producing significantly more ATP than anaerobic processes
- Can last indefinitely as long as oxygen is available
- Important for activities like running, cycling, and hiking
Aerobic Metabolism of Fuels
- Carbohydrates are broken down into glucose, which is then used to generate ATP
- Fats are broken down into fatty acids, which are then used to generate ATP
- Proteins are broken down into amino acids, which are then used to generate ATP
- The respiratory exchange ratio (RER) is used to measure the proportion of carbohydrates and fats being utilized
- RER of 1.0 indicates 100% carbohydrate utilization
- RER of 0.7 indicates 100% fat utilization
Factors Influencing Fuel Utilization
- Exercise intensity: higher intensity favors carbohydrate utilization
- Exercise duration: longer duration favors fat utilization
- Training status: trained individuals utilize fat more efficiently
- Diet: high carbohydrate diets increase carbohydrate utilization
Oxygen Consumption and Exercise
- Oxygen consumption (VO2) increases with exercise intensity
- Steady state exercise is when oxygen consumption plateaus
- Maximum oxygen consumption (VO2max) is the highest rate of oxygen utilization during exercise
- VO2max is a measure of cardiovascular fitness
Oxygen Slow Component
- Oxygen consumption does not immediately reach steady state, but instead increases gradually
- This "slow component" is influenced by the contribution of different energy systems
- During prolonged exercise, the contribution from oxidative phosphorylation increases, which requires a higher oxygen demand
- The slow component can be a factor in limiting maximal work capacity during longer durations of exercise
Rephosphorylation of ATP
- Rephosphorylation is the process of adding a phosphate group back to ADP to create ATP.
- This process is essential for muscle contraction and other cellular processes.
- There are three primary energy systems that contribute to ATP rephosphorylation: creatine phosphate, anaerobic glycolysis, and oxidative phosphorylation (aerobic).
Creatine Phosphate (CP) System
-
Characteristics:
- Provides energy for short, high-intensity activities (e.g., sprinting, jumping).
- Utilizes stored creatine phosphate (CP) to directly rephosphorylate ADP to ATP.
- No metabolic byproducts are produced.
- Limited amount of CP stored within muscle, lasting only about 10-15 seconds of intense activity.
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Replenishment:
- When CP is used up, the body must rely on other energy systems for ATP production.
- During rest or low-intensity activity, CP stores are replenished by using ATP from other sources.
Anaerobic Glycolysis
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Characteristics:
- Provides energy for moderate-intensity activities lasting 30 seconds to 2 minutes (e.g., 400m sprint).
- Breaks down glucose into pyruvate without the presence of oxygen.
- Produces ATP and lactic acid.
- Limited by the buildup of lactic acid in the muscles.
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Replenishment:
- The breakdown of glucose into pyruvate and lactate produces ATP.
- Lactate can be converted back to glucose in the liver.
- Requires more time to recover and remove lactate accumulation than CP system.
Oxidative Phosphorylation
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Characteristics:
- Provides energy for sustained, low-to-moderate intensity activities lasting longer than 2 minutes (e.g., long-distance running).
- Uses oxygen to completely break down glucose, fats, and proteins into ATP.
- Produces significantly more ATP than other energy systems (around 36-38 ATP per glucose molecule).
- Has a higher capacity than other energy systems.
Fuel Utilization in Oxidative Phosphorylation
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Carbohydrate Metabolism:
- Glucose is broken down into pyruvate through glycolysis.
- Pyruvate enters the mitochondria and is converted into acetyl-CoA.
- Acetyl-CoA enters the Krebs cycle where it is further oxidized to produce ATP and electron carriers (NADH and FADH2).
- Electron carriers deliver electrons to the electron transport chain, generating a proton gradient that drives the production of ATP.
-
Fat Metabolism:
- Fats are broken down into glycerol and free fatty acids.
- Glycerol can be converted to glucose.
- Free fatty acids are transported to the mitochondria and broken down into acetyl-CoA, entering the Krebs cycle and electron transport chain to produce ATP.
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Protein Metabolism (amino acids):
- Proteins can be broken down into amino acids that can be converted to glucose or pyruvate and enter the oxidative phosphorylation pathway.
- Protein metabolism is typically a minor source of energy during exercise.
Respiratory Exchange Ratio (RER)
- The ratio of carbon dioxide produced to oxygen consumed (VCO2/VO2) during exercise.
- Reflects the primary fuel source used by the body.
- RER of 1.0 indicates pure carbohydrate utilization.
- RER of 0.7 indicates pure fat utilization.
- The RER value typically shifts towards the carbohydrate end of the spectrum (towards 1.0) during intense exercise.
Factors Influencing Fuel Utilization
- Exercise Intensity: Higher intensity favors carbohydrate metabolism, while lower intensity favors fat metabolism.
- Duration of Exercise: Longer duration favors fat metabolism.
- Training Status: Trained individuals tend to utilize more fat than untrained individuals.
- Diet: Dietary composition of carbohydrate, fat, and protein can influence fuel utilization.
Oxygen Consumption and Exercise Intensity
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Steady-State Exercise:
- During submaximal, steady-state exercise, oxygen consumption (VO2) reaches a plateau.
- VO2 at steady-state is directly proportional to exercise intensity.
- The plateau represents the balance between energy demand and oxygen supply.
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Maximal Oxygen Consumption (VO2max):
- The highest rate of oxygen consumption that the body can achieve during maximal exercise.
- Represents the body's ability to deliver and utilize oxygen.
- A significant determinant of aerobic endurance capacity.
Oxygen Slow Component
- Concept: The slow increase in oxygen consumption after initial steady-state exercise.
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Explanation:
- This phenomenon is related to the energy systems involved.
- During initial exercise, the CP and anaerobic glycolysis systems are predominantly used.
- Over time, as these systems become depleted, oxidative phosphorylation gradually takes over as the primary energy source.
- This shift in energy system utilization leads to a slower, but continuous increase in oxygen consumption.
Connection to Work Capacity
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Work Capacity:
- The maximum amount of work an individual can perform in a given duration of time.
- Work capacity is limited by the aerobic capacity (VO2max)
- The oxygen slow component suggests that even at high intensity, the body doesn't immediately reach its maximum oxygen consumption.
- This means that individuals can sustain high-intensity exercise for a longer period than initially expected, potentially extending their work capacity.
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Description
This quiz explores the different energy systems utilized during exercise, including the Creatine Phosphate Energy System and Anaerobic Glycolysis. Understand the biochemical processes, duration, and factors influencing fatigue. Test your knowledge of how these systems function during high-intensity workouts.