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Medicine 2.1 > Muscle Metabolism and Fatigue > Flashcards

Muscle Metabolism and Fatigue Flashcards

1
Q

What is fatigue?

A

-Inability to maintain power output, reversible by rest.

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2
Q

What do the different types of fatigue all have in common?

A
  • All reduce force and power
  • When fatigue occurs, force, shortening velocity and relaxation rate all decline.
  • Fatigue reduces power as Power = force x velocity
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3
Q

What does recovery time depend on?

A

-Nature of fatigue

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4
Q

What are the 2 types of fatigue?

A
  • Peripheral

- Central

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5
Q

What is peripheral fatigue?

A

-Fatigue within muscle fibres

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6
Q

What may cause peripheral fatigue?

A
  • Failure of excitation-contraction coupling, T-tubule AP, SR activation, Ca2+ release
  • Failure of force generation at cross bridge
  • Failure of ATP generation by depletion of energy stores
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7
Q

What is central fatigue?

A

-Fatigue within the nervous system

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8
Q

What may cause central fatigue?

A
  • Loss of excitability of motor complex
  • Probable reflex inputs from metabo receptors in muscle
  • Can include failure of transmission in peripheral nerve and neuromuscular junctions
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9
Q

How can central and peripheral fatigue be distinguished?

A
  • External stimulation can help identify site of fatigue:
  • If direct muscle stimulation delivers smaller forces then the fatigue is peripheral.
  • If the muscle stimulation delivers normal forces then the fatigue is central.
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10
Q

When may central fatigue occur?

A
  • Probably important in occupational work
  • Recreational sport
  • Sensation of fatigue may involve discomfort and lack of motivation so is probably not a factor in elite sport.
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11
Q

When may peripheral fatigue occur?

A

-Nerve conduction and NMJ transmission failure but this is unlikely

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12
Q

Can fatigue be due to reductions in ATP?

A

NO

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13
Q

What happens when ATP runs out?

A

-Muscle goes into rigour not fatigue

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14
Q

What happens when ADP, Pi, H+ all increase?

A
  • Impairs calcium fluxes and impairs force delivery at cross bridges.
  • At ATPase site inhibits function (cross bridges)
  • Inhibit Ca release and reuptake into SR, this affects force and speed of shortening and relaxation, H+ also competes with Ca for troponin binding.
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15
Q

What affect does short duration/high power activity have on energy stores?

A

-ATP regenerated by breakdown of creatine phosphate

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16
Q

What affect does moderate duration/low power activity have on energy stores?

A

-Depletion of glycogen potentially a problem (after 1-3hrs activity)

17
Q

What affect does long duration activity have on energy stores?

A
  • Lipid metabolism starts after around 90% of initial glycogen has been used.
  • Lipids come from adipocytes and intramuscular stores
  • Very long duration activities utilise lipids almost entirely
18
Q

What motor units play a role in long duration activity?

A

-Low power type 1 units

19
Q

What motor units play a role in moderate duration activity?

A

-Slow and FFR units

20
Q

What motor units play a role in short duration activity?

A

-All units active

21
Q

What type of training would be done for strength?

A
  • Small no. of reps, high force contractions

- Sometimes called resistance training

22
Q

What can be the results of strength training?

A
  • Can increase muscle mass
  • 2x and 2B muscle fibres enlarge
  • Muscle strength gain has 2 phases:
  • First 4-6 weeks ‘neural’ as activation of motor unit improves.
  • Then hypertrophic as large motor unit grows.
  • Connective tissues also strengthen
23
Q

What type of training would be done for endurance?

A

-Many reps, low force contractions

24
Q

What can be the result of endurance training?

A
  • Can reduce muscle mass
  • Type 1 fibres may enlarge
  • 2x fibres decrease
  • 2a fibres response is variable
  • Usually loss of fat mass as body weight decreases
  • Mostly leads to enhanced aerobic metabolism
  • Improved cardiovascular performance
  • Improved metabolic performance
25
Q

Describe hypertrophy in strength training?

A
  • Slow
  • Starts with development of new contractile filaments added laterally to existing myofibrils
  • Later there is fibril splitting, the most enlarged fibrils divide longitudinally. Thus fibrils become more numerous.
26
Q

What does improved cardiovascular performace include?

A
27
Q

What does improved metabolic performace include?

A
  • Improved enzyme conc.
  • Improved mitochondrial density
  • Better substrate storage and mobilisation

Medicine 2.1 (29 decks)

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