W2 - Peripheral Fatigue Flashcards
What is meant by fatigue during maximal exercise?
Inability to maintain a given or expected power or work output.
Maximal exercise
Can only be sustained for seconds to minutes
Greater than 100% VO2 max
Where is the majority of ATP re-synthesis derived from for maximal exercise?
PCr hydrolysis
Anaerobic glycolysis
Some aerobic CHO utilisation
What happens to relative oxidative ATP production as ATP demand of contraction increases due to exercise intensity increasing?
Declines + theres greater reliance on non-oxidative ATP production.
How many moles of ATP are used per 60seconds of max exercise?
4.4
What is performance during maximal exercise limited by?
Inability to maintain extremely high rates of ATP turnover.
What must there be an increase in the contribution from if maximal exercise is to be continued beyond only a few seconds?
Must be an increase from glyogenolysis + glycolysis to ATP re-synthesis
What stimulates glycogenolysis?
Accumulation of the products of ATP + PCr hydrolysis
When does force decline?
When theres an inability to maintain high rates of ATP production + fatigue is inevitable.
What is important for subsequent bouts of exercise?
Muscle PCr re-synthesis
What can Pi interfere with?
Ca2+ sensitivity, release + availability.
Increasing Pi can impair Pi release from the myosin head during the power stroke.
What can the stimulation of SR Ca2+ release by caffeine improve?
Muscle force production in vitro, even when muscle pH is low.
What is Ca2+ re-uptake dependent on?
ATP
What can local PCr depletion do?
Reduce SR re-uptake
What may extracellular K+ accumulation do during high intensity exercise?
Impair performance
Define sub maximal exercise
Exercise that can be sustained for over a few mins up to 3 hrs before fatigue.
Exercise intensity of 100-60% of maximal O2 consumption (VO2max)
Why might the rate of fat oxidation decline when transitioning to high-intensity, sub maximal exercise?
Breaking down fats to provide energy takes a while due to numerous steps involved.
Instead, CHO breakdown takes over due to being a faster process with fewer steps.
Is glycogen availability limiting to ATP re-synthesis during maximal exercise?
No
Rate of glycolysis decreases despite glycogen being availability,
By-products of glycolysis impair the muscle function by creating an acidic environment.
How might CHO supplementation delay fatigue during submit exercise?
CHO supplementation increases the amount of free glucose in the blood.
= Body doesn’t need to go through process of breaking down glycogen in muscle until later on in exercise = delays fatigue
Why might H+ accumulation cause fatigue?
Accumulation of H+ = decreases pH = could affect PFK enzyme so can’t break down glucose to yield energy in glycolysis.
= Reduces energy available for contraction = fatigue
Increased ability to remove H+ + delay the drop in pH has been shown to increase rates of glycolysis.
Why does acetylcarnitine accumulation prior to sub maximal exercise reduce fatigue development?
Acetylcarnitine is created during glycolysis.
At onset of exercise, acetylcarnitine can be used to decrease the reliance on PCr stores + improve perf + delay fatigue.
Dichloroacetate (DCA)
Pharmacological analogue of pyruvate that activates PDC + ‘stockpiles’ acetylcarnitine.
= Reduces reliance on non-oxidative ATP re-synthesis.
Better matching of what can improve performance?
Better matching of glycolytic flux to TCA flux improves performance
How can a ‘warm-up’ exercise help with acetylcarnitine
Prior ‘warm-up’ exercise ‘stockpiles’ acetylcarnitine & reduces reliance on non-oxidative ATP production.
