1. Metabolic Responses to Endurance Exercise Flashcards
Define Endurance Exercise
Exercise that utilises mainly aerobic metabolism to provide energy for muscle contraction.
Muscle require adequate 02 + fuel (carbs + fats)
Low - moderate intensity (exc. endurance athletes)
Prolonged duration (>30 mins)
Energy type used for muscle contraction
ATP
ATP - ADP + Pi + Energy
What is Pi
Free Inorganic phosphate
Enzyme that catalyses hydrolysis of ATP
ATPase
Intramuscular ATP
Immediately available BUT limited supply
7.3 kcal available
Few secs of max exercise
3 basic energy systems
- ATP-PCr system
- Glycolytic system (glycolysis)
- Oxidative system (oxidative phosphorylation)
Phosphocreatine (PCr) Breakdown Equation
PCr - Cr + Pi + ENERGY
Phosphocreatine (PCr) Breakdown (5 points)
- Intramuscular store of PCr
- Immediately available
- Enzyme – creatine kinase
- V rapid ATP resynthesis
- Very limited store - 6 - 10 s max exercise
Creatine Kinase
Enzyme that catalyses hydrolysis of phosphocreatine molecule
How is energy for ATP resynthesis produced
Breakdown of glucose or glycogen
Storage form of glucose
Glycogen
Anaerobic Glycolysis Equation
Glucose/ glycogen - 2 pyruvate + ENERGY
Where does Anaerobic Glycolysis occur
Cytoplasm (where relevant enzymes are available)
Primary enzyme of glycogen breakdown
Glycogen phosphorylase
ATP yield of Anaerobic Glycolysis
2-3 ATP
End point of glycolysis
Two molecules of produced go through aerobic and anaerobic reaction, producing lactate and oxidation (…)
Anaerobic Glycolysis in exercise (4 points)
- Does not produce large amounts ATP
- Combines with ATP-PCr system for force generation (even when 02 limited)
- Predominate during early mins of high intensity exercise.
- Other system needed for longer during (can’t supply every >2mins)
Limitations of Anaerobic Glycolysis (3 points)
- Build up of lactic acid in muscles and body fluids
- Decreases muscle fibres’ calcium-binding capacity, impedes
muscle contraction - Acidification inhibits further glycogen breakdown, impairs
glycolytic enzyme function
Most complex of energy systems
Oxidative system
Process of cellular respiration (oxidative system)
Body breaking down substrates with aid of O2 to generate energy
Site of Oxidative production of ATP
Mitochondria
Why do muscles need steady supply of energy during long activity
To continuously produce force needed to sustain exercise
Oxidative system capacity
Large energy-producing capacity
Primary method of energy production for what activity
Endurance
Speed of oxidative system to turn on
Slow
Oxidation of Carb equation
Pyruvate (anaerobic glycolysis) - C02 + H20 + ENERGY
What is pyruvate converted into (Oxidation of Carb)
acetyl coenzyme-A in mitochondria - Krebs cycle - electron transport train
Net yield of Oxidation of carbs
38-39 ATP
Oxidation of fat equation
Plasma free fatty acids/ intramuscular triglyceride - C02 + H20 + ENERGY
What is substrates converted into (Oxidation of Fat)
acetyl coenzyme-A (in mitochondria) → Krebs Cycle
→ electron transport chain
Speed and net yield of ATP (resynthesis)
Slow, 130 ATP
Carb stores capacity
Limited
Fat stores capacity
Large
What is fat stored as
triacylglycerol (fatty acids + glycerol)
Where is fat stored
adipose tissue, some skeletal muscle
Fat vs carb fuel storage
9 : 4
Process of breaking down triacylglycerol
lipolysis:
release free fatty acids into plasma - transported to exercising muscle
Enzyme that catalyses process of lipolysis
Hormone-sensitive lipase
Muscle glycogen v liver glycogen v plasma glucose v fat energy comparison
- fat (93,000) (4,900 mins)
- muscle glycogen (1600) (80 mins)
- liver glycogen (400) (20 mins)
- plasma glucose (40) (2 mins)
Use of blood glucose (Glucose/ Glycogen Interaction) regulated by
regulated by availability of
GLUT4 + hexokinase
What is hexokinase
enzyme inhibited by rapid glycogen breakdown
Fuel used in early exercise
Mainly glycogen
Fuel used in later exercise
Less glycogen (stores reduced)
More glucose (hexokinase inhibition lifted)
What is lipolysis regulated by
Adipose tissue blood flow
Effect of prolonged exercise on blood flow
Increase 50% V02 max
reduced blood flow in intense exercise causes:
release of FFA
increased lactate in intense exercise promotes:
formations of triglyceride
Onset of exercise (3 points) causes:
- Immediate energy from PCr + anaerobic glycolysis (+oxidation)
- Fast and immediately available
- PCr stores limited + anaerobic glycolysis inefficient (low yield)
Continued exercise (2 points) causes: (energy store used)
- less utilisation of blood glycogen (store
reduced) - more utilisation of blood glucose (+ reduction of liver glycogen store)
Further exercise (4 points) causes :
- > 2hrs fat oxidation max rate
- increased fat utilisation (more efficient) high yield
- limited glycogen store
- slow, limited intensity
