Fat & Carbohydrate Exercise Physiology Flashcards Preview

DEMS: Unit II > Fat & Carbohydrate Exercise Physiology > Flashcards

Flashcards in Fat & Carbohydrate Exercise Physiology Deck (6)
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1

Fuel use based on exercise intensity: high vs. low intensity

  • Fat and carbohydrate (CHO) generate ATP during aerobic exercise. Depending on the level of fitness of an individual, fat can sustain the biggest part of ATP production.
  • At low exercise intensities fat is the preferred substrate although there is always some glucose oxidation.  Used when VO2 max is up to 75%                           
  • CHO metabolism is of great importance during exercise, especially during high exercise intensity where it is the predominant energy substrate for skeletal muscle.  Used when VO2 max >75%.

 

2

Mechanism of metabolism used in muscles during very high intensity exercise

  • When exercise intensities are very high/close to maximal (above 100% of VO2 max) ATP cannot be generated by the aerobic mechanism
  • ATP generated through the anaerobic mechanism also called substrate level phosphorylation
  • ATP synthesis derived from CHO is much faster and therefore the choice of substrate by skeletal muscle fibers during faster twitch, high exercise intensities.

3

Metabolic adaptations caused by training

  • After training = ↓ work intensity, ↓ glycolytic flux, ↓ glycogenolysis, ↓ energy requirement from glucose
  • In trained individuals, higher exercise intensities cause lower  blood lactate accumulation due to increased lactate clearance capacity through an increase in mitochondrial lactate dehydrogenase (mLDH)
  • Mitochondrial density and oxidative enzymes increase with training and this increases the capacity for fat utilization.
    • Endurance training can double the mitochondrial capacity to oxidize FFA and pyruvate.

4

Importance of glycogen for exercise

  • Muscle glycogen is crucial for ATP synthesis during exercise.
  • Proper glycogen storages are of great importance for athletic performance.
  • Multiple studies show that fatigue and decrease in performance is often associated with glycogen depletion and that athletes who have low carbohydrate diets or low glycogen storages 

5

Role of lactate during exercise

  • Lactic acid is the byproduct of glycolysis. 
  • During competitive exercise ATP generation demands increase and glucose becomes the predominant muscle substrate for ATP generation.
    • The higher the glucose flux into the cell the higher the lactate production.
  • Lactate production is necessary for the continuation of glycolysis
  • Lactate is an important carbohydrate source and a main gluconeogenic precursor during exercise as it is shuttled to other cells, tissues and organs where about 75-80% is oxidized to pyruvate for energy purposes.
  • Lactate accumulation inhibits lipolysis at high exercise intensities → similar to ↑ epi.

6

Fitness testing parameters

  • VO2 max is meaningless. Average athletes can have higher than pros.
  • Muscle lactate metabolism is much more useful and can subdivide beginners and pros from amount of lactate produced with increasing exercise workload.