Exercise metabolism Flashcards
When is highest rate of fat oxidation reached?
just before lactate threshold
Blood lactate does not cause muscle soreness
lactate removal is rapid (<60 mins)
DOMS
delayed onset muscle soreness
What causes DOMS?
microscopic injury to muscle fibres = slow cascade of biochemical events leading to inflammation and edema
Lactate shuttle
produced in one tissue and transported to another to be used as an energy source
through Cori cycle via gluconeogenesis
Cori cycle
cycle of lactate/glucose between the muscle/liver
Crossover concept
the shift from fat to CHO metabolism as exercise intensity increases
due to:
recruitment of fast muscle fibres
increasing blood levels of epinephrine stimulate glycolysis and lactate production (inhibit fat metabolism by reduce availiability of fat as a substrate)
Beta oxidation
process of oxidizing fatty acids to Acetyle-CoA
Why is glycogen depleted during prolonged (>2 hrs) high-intensity exercise)?
decreased rate of glycolysis and production of pyruvate
decreased rate of krebs-cycle activity
Fats burn in the flame of carbohydrates
decreased intermediates also decrease rate of fat oxidation
fats can only be metabolized via krebs-cycle oxidation
ingestion of sports drinks (30-60g of CHO/hr) can improve endurance performance
Influence of exercise intensity on fuel source
increased rate of glycogenolysis due to recruitment of fast-twitch fibres and elevated blood epinephrine levels
Influence of exercise duration on fuel source
due to an increased rate of lipolysis
breakdown of triglycerides (by lipases) –> glycerol + FFA
stimulated by rising blood levels of hormones - epinephrine, norepinephrone and glucagon
Lactate threshold
the point at which blood lactic acid rises systematically during incremental exercise
4 mmol/L
anaerobic threshold
Lactate threshold in untrained athletes
50-60% VO2max
Lactate threshold in endurance trained athletes
65-80% VO2max
