Neuromuscular system

• Nervous system -

  The sympathetic nervous system prepares the body for exercise and is often referred to as the 'fight or flight response'.

  The parasympathetic nervous system - relaxes the body and slowing down many high energy functions.
• Types of muscle fibres - Slow oxidative type I -

  • have a slower contraction speed and are better adapted to lower intensity such as long-distance running.
  • They produce most of their ATP aerobically and are therefore more able to use oxygen more effectively.
• Fast twitch fibres - type II - faster contraction speed and generate most of their ATP anaerobically.

  • Type IIa fast oxidative glycolytic fibres are more resistant to fatigue and are used for events such as the 1500m in athletics where a longer burst of energy is needed.
  • type IIx fast glycolytic fibres fatigue much quicker than type IIa and are used for highly explosive events such as the 100m in athletics where a quick short burst of energy is needed.
• Motor units -

  consist of one motor neurone and a group of muscle fibres. Only one type of muscle fibre can be found in one particular motor unit. The motor neurone transmits the nerve impulse to the muscle fibre.

  All or none law -

  Once the motor neurone stimulates the muscle fibres, either all of them contract or none of them do. A minimum amount of stimulation (threshold) is needed to start a contraction. If the sequence of impulses is equal to or more than the threshold, all muscle fibres within a unit will contract.
• To increase the strength of a contraction -

  • wave summation - a repeated nerve impulse with no time to relax, resulting in a smooth, sustained contraction.
  • Tetanic contraction - a sustained, powerful muscle contraction caused by a series of fast repeating stimuli.
  • Spatial summation - when the strength of a contraction changes by altering the number and size of the muscle's motor units. recruitment additional, bigger motor units.
• Proprioceptive neuromuscular facilitation - (PNF) - advanced stretching technique that trains and improves flexibility and range of motion.

  • Muscle spindles - proprioceptors that detect how far and fast a muscle is being stretched (excitory signals) and produce the stretch reflex. This is where the muscle contracts to prevent overstretching.
  • Golgi tendon organs - These detect levels of tension within a muscle as it is being stretched and they send inhibitory signals to allow the muscle to relax and lengthen in what is known as autogenic inhibition.