W2 - Peripheral Fatigue

Question 1

What is meant by fatigue during maximal exercise?

Answer 1

Inability to maintain a given or expected power or work output.

Question 2

Maximal exercise

Answer 2

Can only be sustained for seconds to minutes

Greater than 100% VO2 max

Question 3

Where is the majority of ATP re-synthesis derived from for maximal exercise?

Answer 3

PCr hydrolysis

Anaerobic glycolysis

Some aerobic CHO utilisation

Question 4

What happens to relative oxidative ATP production as ATP demand of contraction increases due to exercise intensity increasing?

Answer 4

Declines + theres greater reliance on non-oxidative ATP production.

Question 5

How many moles of ATP are used per 60seconds of max exercise?

Answer 5

4.4

Question 6

What is performance during maximal exercise limited by?

Answer 6

Inability to maintain extremely high rates of ATP turnover.

Question 7

What must there be an increase in the contribution from if maximal exercise is to be continued beyond only a few seconds?

Answer 7

Must be an increase from glyogenolysis + glycolysis to ATP re-synthesis

Question 8

What stimulates glycogenolysis?

Answer 8

Accumulation of the products of ATP + PCr hydrolysis

Question 9

When does force decline?

Answer 9

When theres an inability to maintain high rates of ATP production + fatigue is inevitable.

Question 10

What is important for subsequent bouts of exercise?

Answer 10

Muscle PCr re-synthesis

Question 11

What can Pi interfere with?

Answer 11

Ca2+ sensitivity, release + availability.

Increasing Pi can impair Pi release from the myosin head during the power stroke.

Question 12

What can the stimulation of SR Ca2+ release by caffeine improve?

Answer 12

Muscle force production in vitro, even when muscle pH is low.

Question 13

What is Ca2+ re-uptake dependent on?

Answer 13

ATP

Question 14

What can local PCr depletion do?

Answer 14

Reduce SR re-uptake

Question 15

What may extracellular K+ accumulation do during high intensity exercise?

Answer 15

Impair performance

Question 16

Define sub maximal exercise

Answer 16

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)

Question 17

Why might the rate of fat oxidation decline when transitioning to high-intensity, sub maximal exercise?

Answer 17

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.

Question 18

Is glycogen availability limiting to ATP re-synthesis during maximal exercise?

Answer 18

No

Rate of glycolysis decreases despite glycogen being availability,

By-products of glycolysis impair the muscle function by creating an acidic environment.

Question 19

How might CHO supplementation delay fatigue during submit exercise?

Answer 19

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

Question 20

Why might H+ accumulation cause fatigue?

Answer 20

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.

Question 21

Why does acetylcarnitine accumulation prior to sub maximal exercise reduce fatigue development?

Answer 21

Acetylcarnitine is created during glycolysis.

At onset of exercise, acetylcarnitine can be used to decrease the reliance on PCr stores + improve perf + delay fatigue.

Question 22

Dichloroacetate (DCA)

Answer 22

Pharmacological analogue of pyruvate that activates PDC + ‘stockpiles’ acetylcarnitine.

= Reduces reliance on non-oxidative ATP re-synthesis.

Question 23

Better matching of what can improve performance?

Answer 23

Better matching of glycolytic flux to TCA flux improves performance

Question 24

How can a ‘warm-up’ exercise help with acetylcarnitine

Answer 24

Prior ‘warm-up’ exercise ‘stockpiles’ acetylcarnitine & reduces reliance on non-oxidative ATP production.