S2L8 Peripheral Fatigue I

Question 1

What is the definition of fatigue and the main sites of fatigue?

Answer 1

= failure to MAINTAIN the required or expected force or power
- central fatigue - brain
- peripheral fatigue - within muscle
- electrical stimulation used to identify source of fatigue

Question 2

How is calcium associated with peripheral fatigue?

Answer 2

• Ca needed for contraction to occur –> it attaches to troponin, moving tropomysosin out of way. allows binding of actin to myosin, contraction occurs
• reduced Ca means contractions cannot occur

Question 3

How does Ca affect the fibres types, and how can caffeine affect Ca release?

Answer 3

• type II – fatigue quicker so reduced Ca release
• type I - unfatiguable
• caffeine can increase Ca thus delaying fatigue

Question 4

How can the release of Ca be a negative when fatigued?

Answer 4

• decreased ATP - contraction cant occur
• high ADP and AMP - Acidosis
• magnesium doubles as ADP and AMP have lower affinity for it compared to ATP

Question 5

How is the Na-K Pump associated with peripheral fatigue?

Answer 5

• as we fatigue, lower Na-K ATPase activity causing the pump work rate to slow
• cause longer time to restablish resting potential
• therefore delays in producing action potential – delay in ability to build up force
• build up of K in extracellular space causes blunted action potential

Question 6

How is inorganic phosphate associated with perip

Answer 6

• when fatigued - PCR increases and Pi increases.
• Pi can form Ca phosphate which decreases the amount of free Ca by binding to it - less Ca to cause contraction

Question 7

How is pH associated with peripheral fatigue

Answer 7

a decrease in pH may cause fatigue but not the only factor. force recovers faster than pH

Question 8

What is the theory behind ATP depletion?

Answer 8

• localised ATP depletion in space between T tubules and SR (the triad junction.
• this is where most ATP is used to generate movement
• compartmentalisation explains contradictions in different cell parts:
• ADP tightly regulated and does not accumulate
• avg ATP levels do not decreases enough to decrease cross bridge function

Question 9

How can CHO feeding affect fatigue?

Answer 9

• higher glycogen levels so increased TTFatigue
• increased glucose and maintained CHO oxidation
• Ca uptake is stable for longer