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Muscle Fibre Types and Fatigue in Exercise

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12 Questions

What is the primary function of slow-twitch fibres in the human body?

To provide stabilization and support during low-intensity, long-duration activities

What is the typical distribution of slow-twitch fibres in human skeletal muscles?

40-60%

What is a characteristic of fast-twitch fibres that distinguishes them from slow-twitch fibres?

High force production

What type of muscle fibre is more prone to fatigue?

Fast-twitch fibres

What is a factor that contributes to muscle fatigue?

All of the above

What is the definition of muscle fatigue?

A decline in muscle force production over time

What is the primary advantage of high myoglobin content in slow-twitch fibres?

Increased oxygen storage and delivery, allowing for efficient endurance activities

How do the muscle fibre distributions of endurance athletes and sprint athletes differ?

Endurance athletes have a higher proportion of slow-twitch fibres, while sprint athletes have a higher proportion of fast-twitch fibres

What is the role of calcium ion release and uptake in muscle fatigue?

Disruption of calcium ion release and uptake contributes to muscle fatigue

What is the primary difference between slow-twitch and fast-twitch fibres in terms of their anaerobic and aerobic capacities?

Slow-twitch fibres have low anaerobic capacity and high aerobic capacity, while fast-twitch fibres have high anaerobic capacity and low aerobic capacity

What is the effect of sedentary lifestyle on muscle fibre distribution?

Sedentary individuals tend to have a lower proportion of slow-twitch fibres

How does the accumulation of lactic acid and other metabolic byproducts contribute to muscle fatigue?

It disrupts the normal functioning of muscle cells, leading to a decline in muscle force production

Study Notes

Muscle Fibre Types

Slow-twitch Fibres

  • Also known as Type I fibres
  • Characteristics:
    • High endurance and resistance to fatigue
    • Low force production
    • High myoglobin content, allowing for high oxygen storage
    • High mitochondrial density, allowing for efficient aerobic energy production
  • Functions:
    • Designed for low-intensity, long-duration activities (e.g., distance running)
    • Play a crucial role in posture, balance, and stabilisation

Muscle Fibre Distribution

  • Human skeletal muscles consist of a mixture of fibre types
  • Typical distribution:
    • Type I (slow-twitch): 40-60%
    • Type IIA (fast-twitch): 20-40%
    • Type IIB (fast-twitch): 10-30%
  • Distribution can vary depending on factors such as:
    • Muscle group (e.g., leg muscles tend to have more Type I fibres)
    • Training status (e.g., endurance-trained athletes tend to have more Type I fibres)
    • Genetics

Fast-twitch Fibres

  • Also known as Type II fibres (subdivided into Type IIA and Type IIB)
  • Characteristics:
    • High force production
    • Low endurance and high fatigue rate
    • Low myoglobin content, limiting oxygen storage
    • Low mitochondrial density, relying on anaerobic energy production
  • Functions:
    • Designed for high-intensity, short-duration activities (e.g., sprinting)
    • Important for rapid, powerful movements

Muscle Fatigue

  • Defined as a decline in muscle force production over time
  • Types of fatigue:
    • Peripheral fatigue: due to changes in the muscle itself (e.g., ion imbalance, metabolic byproducts)
    • Central fatigue: due to changes in the nervous system (e.g., reduced motor neuron activation)
  • Factors contributing to muscle fatigue:
    • Muscle fibre type (fast-twitch fibres are more prone to fatigue)
    • Intensity and duration of exercise
    • Environmental factors (e.g., temperature, humidity)
    • Nutritional and hydration status

Understand the characteristics, functions and distribution of slow-twitch and fast-twitch muscle fibres, and learn about muscle fatigue and its contributing factors. This quiz covers the basics of muscle physiology and exercise science.

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