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HMS, BM EQ-Bank 830

Compare and contrast the characteristics and functions of slow-twitch and fast-twitch muscle fibres in relation to different sporting activities.   (5 marks)

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Sample Answer

  • Slow-twitch (Type I) fibres have a high mitochondrial and capillary density, enabling efficient aerobic metabolism for sustained, lower-intensity activities like marathon running or cycling.
  • Fast-twitch (Type II) fibres have greater glycolytic capacity and faster contraction speeds, making them suited for explosive, high-intensity activities like sprinting or weightlifting.
  • Slow-twitch fibres are more resistant to fatigue due to their aerobic nature, while fast-twitch fibres fatigue more quickly as they rely primarily on anaerobic metabolism.
  • Endurance athletes typically have a higher percentage of slow-twitch fibres in relevant muscles, while power athletes generally have a higher proportion of fast-twitch fibres.
  • The distribution of fibre types is partly genetically determined, which may predispose individuals toward success in certain sports, though training can optimise the performance of existing fibres.
  • Most muscles contain a mixture of both fibre types, allowing for adaptation to various movement demands, with the specific ratio influencing an athlete’s natural aptitude for either power or endurance activities.
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Sample Answer

  • Slow-twitch (Type I) fibres have a high mitochondrial and capillary density, enabling efficient aerobic metabolism for sustained, lower-intensity activities like marathon running or cycling.
  • Fast-twitch (Type II) fibres have greater glycolytic capacity and faster contraction speeds, making them suited for explosive, high-intensity activities like sprinting or weightlifting.
  • Slow-twitch fibres are more resistant to fatigue due to their aerobic nature, while fast-twitch fibres fatigue more quickly as they rely primarily on anaerobic metabolism.
  • Endurance athletes typically have a higher percentage of slow-twitch fibres in relevant muscles, while power athletes generally have a higher proportion of fast-twitch fibres.
  • The distribution of fibre types is partly genetically determined, which may predispose individuals toward success in certain sports, though training can optimise the performance of existing fibres.
  • Most muscles contain a mixture of both fibre types, allowing for adaptation to various movement demands, with the specific ratio influencing an athlete’s natural aptitude for either power or endurance activities.

HMS, BM EQ-Bank 829 MC

Which characteristic of fast-twitch muscle fibres makes them most suitable for high-intensity, short-duration activities?

  1. High myoglobin content
  2. Abundant mitochondria
  3. High glycolytic capacity
  4. Slow contraction velocity
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Consider Option C: 

  • Fast-twitch muscle fibres have a high glycolytic capacity, allowing them to rapidly produce energy through anaerobic pathways, which is essential for high-intensity, short-duration activities.

Other Options:

  • A is incorrect: High myoglobin content is a characteristic of slow-twitch fibres, helping them use oxygen efficiently for aerobic metabolism.
  • B is incorrect: Abundant mitochondria are characteristic of slow-twitch fibres, supporting their aerobic energy production for endurance activities.
  • D is incorrect: Fast-twitch fibres have fast (not slow) contraction velocity, enabling rapid force production.

HMS, BM EQ-Bank 828 MC

A marathon runner is more likely to have a higher percentage of which type of muscle fibres in their leg muscles?

  1. Fast-twitch fibres
  2. Slow-twitch fibres
  3. Intermediate fibres
  4. Explosive fibres
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Consider Option B: 

  • Slow-twitch muscle fibres have greater endurance capacity due to their aerobic nature, making them ideal for long-duration, lower-intensity activities like marathon running.

Other Options:

  • A is incorrect: Fast-twitch fibres are better suited for short, explosive activities rather than endurance events.
  • C is incorrect: “Intermediate fibres” is not a standard classification of muscle fibres.
  • D is incorrect: “Explosive fibres” is not a standard classification of muscle fibres.

HMS, BM EQ-Bank 37

Describe TWO characteristics and functions of fast twitch muscle fibres.  (3 marks)

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Sample Answer

  • Fast twitch fibres have fewer mitochondria compared to slow twitch fibres
  • They rely primarily on anaerobic glycolysis for energy production
  • They are capable of producing greater force in a shorter time period
  • They fatigue more quickly than slow twitch fibres due to their energy system reliance
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Sample Answer

  • Fast twitch fibres have fewer mitochondria compared to slow twitch fibres
  • They rely primarily on anaerobic glycolysis for energy production
  • They are capable of producing greater force in a shorter time period
  • They fatigue more quickly than slow twitch fibres due to their energy system reliance

HMS, BM EQ-Bank 36

Explain the relationship between muscle fibre types and the production of movement.  (4 marks)

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Sample Answer

Structural Characteristics

  • Type I fibres have more mitochondria and are smaller in diameter, allowing them to contract steadily but with less force, making them suited for postural control and sustained movements.

  • Type II fibres are larger in diameter with fewer mitochondria, enabling them to contract quickly and produce greater force for powerful movements like jumping or lifting.

Production of movement

  • These fibre types work together but are recruited differently.

    • Type I fibres are recruited first for basic movements and maintaining posture.

    • When more force is required, Type II fibres are recruited to produce more powerful movements.

  • This relationship between fibre types allows for a range of movement capabilities, from maintaining balance to producing explosive actions.

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Sample Answer

Structural Characteristics

  • Type I fibres have more mitochondria and are smaller in diameter, allowing them to contract steadily but with less force, making them suited for postural control and sustained movements.

  • Type II fibres are larger in diameter with fewer mitochondria, enabling them to contract quickly and produce greater force for powerful movements like jumping or lifting.

Production of movement

  • These fibre types work together but are recruited differently.

    • Type I fibres are recruited first for basic movements and maintaining posture.

    • When more force is required, Type II fibres are recruited to produce more powerful movements.

  • This relationship between fibre types allows for a range of movement capabilities, from maintaining balance to producing explosive actions.

HMS, BM EQ-Bank 35

Compare the basic characteristics of fast and slow twitch muscle fibres.  (4 marks)

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Sample Answer

  • Contrasts in fibre size/diameter
  • Differences in mitochondrial density
  • Variations in capillary network
  • Differences in contraction speed capabilities
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Sample Answer

  • Contrasts in fiber size/diameter
  • Differences in mitochondrial density
  • Variations in capillary network
  • Differences in contraction speed capabilities

HMS, BM EQ-Bank 34

Outline TWO structural characteristics of slow twitch muscle fibres.  (3 marks)

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Sample Answer

  • High number of mitochondria
  • Extensive capillary network
  • High myoglobin content
  • Smaller in diameter than fast twitch fibres
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Sample Answer

  • High number of mitochondria
  • Extensive capillary network
  • High myoglobin content
  • Smaller in diameter than fast twitch fibres

HMS, BM EQ-Bank 33 MC

Which statement about Type I (slow twitch) muscle fibres' physiological adaptations is INCORRECT?

  1. They have high oxidative capacity
  2. They produce rapid, powerful contractions
  3. They have high fatigue resistance
  4. They support endurance activities
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Type I (slow twitch) muscle fibres:

  • Are characterised by slower contraction speeds and lower power output compared to Type II fibres.
  • Have excellent fatigue resistance and oxidative capacity for endurance activities.
  • Do not produce rapid, powerful contractions – this is a characteristic of Type II (fast twitch) muscle fibres.

HMS, BM EQ-Bank 32 MC

Which characteristic best describes Type IIb (fast twitch) muscle fibres?

  1. High mitochondrial density
  2. Slow contraction speed
  3. Rapid force production
  4. High fatigue resistance
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Considering all Options:

A. High mitochondrial density – INCORRECT

  • This is actually a characteristic of Type I (slow twitch) fibres
  • Type IIb fibres have relatively low mitochondrial density
  • This feature wouldn’t support their primary function of rapid force production

B. Slow contraction speed – INCORRECT

  • This is the opposite of Type IIb fibre characteristics
  • Type IIb fibres have fast contraction speeds
  • This is a characteristic of Type I (slow twitch) fibres

C. Rapid force production – CORRECT

  • Type IIb (fast twitch) muscle fibres are characterised by their ability to produce rapid, powerful contractions.
  • This is their primary distinguishing characteristic and function within the muscular system.

D. High fatigue resistance – INCORRECT

  • Type IIb fibres fatigue quickly
  • High fatigue resistance is a characteristic of Type I (slow twitch) fibres
  • Type IIb fibres’ rapid force production capability means they tire quickly