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Exercise Physiology and Pharmacology > Skeletal Muscle Fatigue > Flashcards

Skeletal Muscle Fatigue Flashcards

1
Q

What is an oxygen deficit?

A

The difference in the total amount of oxygen we have consumed in the early stages of exercise (going from anaerobic to aerobic) to the total consumption had we achieved steady state right away.

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2
Q

What is the length of exercise proportional to?

A

The duration of exercise and the intensity of exercise.
ex. shorter, lighter periods of exercise will recover quicker

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3
Q

What does the fast component occur in EPOC?

A

During the first couple of minutes of recovery.

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4
Q

What occurs in the fast component of EPOC?

A
  1. Resaturate hemoglobin and myoglobin with oxygen
  2. Replenish PCr and ATP stores
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5
Q

What does the slow component occur in EPOC?

A

Pulled out from 30 minutes to 24 hours of recovery based on duration and intensity type.

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6
Q

What happens in the slow component of EPOC?

A
  1. Remove any lactic acid produced during the exercise
  2. Increase blood flow to allow for the dissipation of heat
  3. Repairing any damage tissues (increased in blood flow to them)
  4. Restore equilibrium of ions
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7
Q

What are the ways to remove lactic acid?

A
  1. Transport the molecule to the liver where it undergoes gluconeogenesis to make glucose
  2. Lactate excreted into sweat and the urine
  3. Lactate will dissociate into carbon dioxide
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8
Q

How does the heart rate, blood flow, and oxygen consumption compare in the fast component versus slow component of EPOC?

A

During the slow component, heart rate, oxygen consumption, and blood flow have all increased to allow for the dissipation of heat.

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9
Q

What hormones work in the slow component of EPOC?

A

Adrenaline/noradrenaline and thyroxine.

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10
Q

What is central fatigue?

A

The inability of the nervous system to active muscles. For instance, not firing action potentials.

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11
Q

What is peripheral fatigue?

A

What happens within the muscle that can prevent muscle contraction and slow down ATP production.

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12
Q

How do power outputs relate to fatigue?

A

Can maintain power output for a great period of time; however, fatigue would mean a great decline in the power output.

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13
Q

How do maximum power output relate to fatigue?

A

The second, third, fourth, etc. lift will never be as strong as the first one due to the great decline in maximum output.

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14
Q

How does performance rate relate to the duration of exercise?

A

As we keep going on our performance rate declines due to fatigue.

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15
Q

How long can ATP in muscle maintain contractions for?

A

Only 2 seconds

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16
Q

How is the recovery of PCr?

A

Very quick as a second sprint can be performed 1-2 minutes afterwards.

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17
Q

What does lactic acid dissociate into?

A

Lactate and hydrogen ions.

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18
Q

What causes fatigue in high-intensity exercises?

A

Metabolic by-products through product inhibition. NOT depletion of energy stores.

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19
Q

What is product inhibition?

A

Product of an enzyme reaction inhibits its production. Metabolic by products of both metabolic and muscle contraction inhibit further muscle contraction.

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20
Q

How does lactic acid produce fatigue in high intensity exercise?

A
  1. Lactate is inert
  2. Hydrogen ion can lower the intramuscular pH which reduce the force produced
    NOTE: the second one has since been proven false
21
Q

What are the consequences of hydrogen ion buildup?

A
  1. Acidity of H+ ion causes muscle pH to fall
  2. Reduced muscle pH contributes to fatigue via:
    - reduced activity of glycolytic enzymes (especially PFK)
    - interfere with contractile processes (Ca binding to troponin)
    - stimulate nerve endings (burning sensation)
22
Q

Why is it believed that lactic acid doesn’t contribute much to fatigue?

A

The lactic acid trapped in our muscles does not give to fatigue because even though our pH does decrease, the same intensity of exercise is maintained.

23
Q

How does inorganic phosphate contribute to fatigue in high intensity exercises?

A
  1. It can enter the cytosol of muscle cells through SR permeable changes
  2. Combine with free calcium
  3. Results in a precipitate (great time to dissolve)
  4. Calcium cannot be released from the SR when an action potential occurs
  5. This reduces forces of muscle contraction and calcium sensitivity
24
Q

How is inorganic phosphate made?

A

Breakdown of PCr in which its energy is needed for muscle contraction.

25
Q

How does ADP play a role in fatigue in high intensity exercise?

A

ADP has been shown to slow cross bridges cycling rate. This leads to a reduction in the speed of skeletal muscle shortening and contraction velocity.

26
Q

What is power a combination of?

A

Force and velocity

27
Q

What reduces force in the power summination?

A

Phosphate ions.

28
Q

What reduces velocity in the power summination?

A

ADP

29
Q

How does potassium contribute to high intensity exercise fatigue?

A
  1. Periods of depolarization and repolarization happen so quickly that ion balance restorations don’t happen greatly
  2. Loss of potassium from the cell which disrupts the action, potential propagation, and reduces the excitability of the muscle cell (hyperpolarization)
30
Q

How to develop fatigue resistance in anaerobic events?

A
  1. Use of creatine monohydrate increases the intracellular creatinine and PCr stores by 20-25%
31
Q

What is the main source of fuel for the aerobic system?

A

Muscle glycogen

32
Q

What energy stores produce energy quicker?

A
  1. Muscle glycogen
  2. Liver glycogen
  3. Muscle glucose
33
Q

What is the side effect of fatty acid metabolism?

A

They take longer and have an ATP cost in breaking them down.

34
Q

What main energy source are we using at rest?

A

Plasma free fatty acids

35
Q

How does muscle glycogen relate to exercise time?

A

The more we have the longer we can exercise for.

36
Q

What happens after 80 minutes of exercise?

A

Muscle glycogen stores are used up, thus contributing to fatigue.

37
Q

What are the three stores of muscle glycogen?

A
  1. Sub-sarcolemma
  2. Intramyofibrillar
  3. Intermyofibrillar
38
Q

Where is sub-sarcolemma located?

A

Between the cell surface membrane.

39
Q

Where is intramyofibrilliar located?

A

Between contractile filaments located close to the triadic junctions of the SR and t-tubules.

40
Q

Where is intermyofibrillar located?

A

Between myofibrils in contact with longitudinal part of SR.

41
Q

What muscle glycogen store is most depleted during exercise?

A

Intramyofibrilliar store.

42
Q

What is the depletion of the intramyofibrilliar store associated with?

A
  1. Reduced calcium released from the SR
  2. Coupling between the AP and calcium in the glycogen depleted state is damaged
43
Q

What is the hitting the wall phenomenon?

A

The switch to fat metabolism

44
Q

How to lower the hitting the wall phenomenon?

A

Increase pre-exercise muscle glycogen content, which can be manipulated by high carbohydrate diets.

45
Q

What is CHO loading?

A

Eating more carbohydrate strategically over time to increase the activity of the enzyme glycogen kinase (increases the amount of glycogen able to store in muscle). This provides energy for longer.

46
Q

How can CHO feeding during exercise delay fatigue?

A

Once your muscle glycogen store is gone, it uses that glucose that has entered the blood as fuel. It prolongs the performance but doesn’t delay it.

47
Q

What is the main cause of muscle fatigue in prolonged exercise?

A

A failure to resynthesize ATP to maintain the required level of work due to the depletion of muscle glycogen.

48
Q

What are skeletal muscle glycogen stores important?

A

Increasing these stores are the most effective way of prolonged failure.

49
Q
A

Exercise Physiology and Pharmacology (9 decks)

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