HSE201 Lecture Notes - Lecture 6: Fatty Acid-Binding Protein, Adrenal Medulla, Intramuscular Fat
6. Oxidative metabolism of CHO & lipid
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Factors controlling:
Muscle
Liver
Adipose tissue
Fuels during prolonged exercise:
Oxidative catabolism of CHO and lipids
- provides most of the energy to fuel muscle contraction
- except during work-rate transitions, and at high-intensity work rates
Amino acids
- Derived from protein stores
- Make a small contribution to ATP production
Contributions of CHO/lipids
Fuel selection & exercise intensity
- Low (<30%vo2max): fats are primary fuel
- High (>70%VO2max): CHO primary fuel
- Crossover concept: describes the shift from fat to CHO
metabolism as exercise intensity increases, due to
recruitment of fast muscle fibres, increasing blood
levels of epinephrine. →
Exercise duration & fuel selection
- Prolonged exercise: shift from CHO metabolism toward fat
metabolism
- Increased rate of lipolysis: breakdown of triglycerides into
glycerol & FFAs, stim by rising levels of epinephrine
- Increase in blood glucose use as decreased levels of muscle
glycogen & correlates with fatigue
Muscle Glycogen Utilization
Rate of glycogen b/down proportional to exercise intensity
- High-intensity: rapid glycogen depletion
- Low-intensity: slow glycogen depletion
The extent of glycogen depletion is thus partly related to exercise duration
- Short duration: limited glycogen depletion, despite intensity of rapid rate of utilisation
- Long duration: limited glycogen depletion, intensity produces slow rate of utilisation
- Medium duration: maximum glycogen depletion, rapid rate of glycogen utilisation sustained
Major factors
- Requires inorganic phosphate (Pi) as breaking down ATP
- Muscle glycogen catabolism under dual control
- 1. Hormonal control (b-adrenoceptor stimulation by adrenaline, via cyclic AMP 2nd msgr)
- 2. Contraction mediated control (Ca2+ - calmodulin)
Document Summary
Provides most of the energy to fuel muscle contraction. Except during work-rate transitions, and at high-intensity work rates. Make a small contribution to atp production. Crossover concept: describes the shift from fat to cho metabolism as exercise intensity increases, due to recruitment of fast muscle fibres, increasing blood levels of epinephrine. Prolonged exercise: shift from cho metabolism toward fat metabolism. Increased rate of lipolysis: breakdown of triglycerides into glycerol & ffas, stim by rising levels of epinephrine. Increase in blood glucose use as decreased levels of muscle glycogen & correlates with fatigue. Rate of glycogen b/down proportional to exercise intensity. The extent of glycogen depletion is thus partly related to exercise duration. Short duration: limited glycogen depletion, despite intensity of rapid rate of utilisation. Long duration: limited glycogen depletion, intensity produces slow rate of utilisation. Medium duration: maximum glycogen depletion, rapid rate of glycogen utilisation sustained. Requires inorganic phosphate (pi) as breaking down atp.
