Muscle Contraction During Exercise and During Recovery

• Slow Oxidative (Type 1)

  Myoglobin Content: High

  Phosphocreatine Stores: Low

  Mitochondrial Density: High

  Capillary Density: High

  Neuron Size: Small

  Fibres per Neuron: Few
• Fast Oxidative Glycolytic (Type 2a)

  Myoglobin Content: Moderate

  Phosphocreatine Stores: High

  Mitochondrial Density: Moderate

  Capillary Density: High

  Neuron Size: Large

  Fibres per Neuron: Many
• Fast Glycolytic (Type 2b)

  Myoglobin Content: Low

  Phosphocreatine Stores: High

  Mitochondrial Density: Low

  Capillary Density: Low

  Neuron Size: Large

  Fibres per Neuron: Many
• Slow Oxidative

  Speed of Contraction: Slow

  Force of Contraction: Low

  Fatigue Resistance: High

  Aerobic Capacity: High

  Anaerobic Capacity: Low
• Fast Oxidative Glycolytic:

  Speed of Contraction: Fast

  Force of Contraction: High

  Fatigue Resistance: Moderate

  Aerobic Capacity: Moderate

  Anaerobic Capacity: Moderate
• Fast Glycolytic:

  Speed of Contraction: Fast

  Force of Contraction: High

  Fatigue Resistance: Low

  Aerobic Capacity: Low

  Anaerobic Capacity: High
• If a sports performer has a high proportion of slow oxidative fibres they will be better at endurance based activities such as marathon running.
• If a sports performer has a high proportion of fast glycolytic fibres they will be good at high-intensity based activities such as shot put.
• If a sports performer has a high proportion of fast oxidative glycolytic they will be good at team games or speed endurance activities such as hockey.
• If a sports performer has an equal mix of slow oxidative and fast glycolytic fibres they will be good at games type activities such as football.
• When exercising, muscle fibres are always recruited in the order:

  Slow Oxidative

  Fast Oxidative Glycolytic

  Fast Glycolytic
• During light exercise such as marathon running, only slow oxidative fibres are recruited. During moderate intensity exercise, more motor units are stimulated, with slow oxidative fibres being recruited first, followed by fast oxidative glycolytic fibres. During high intensity exercise, slow oxidative fibres are recruited first, followed by fast oxidative glycolytic, then finally fast glycolytic.