Muscles

• An agonist is the muscle responsible for creating movement at a joint. The antagonist that opposes the agonist. A fixator is a muscle that stabilises one part of the body while another moves.
• An isotonic contraction is when the muscles contracting change length. They contract concentrically where the muscle shortens or eccentrically where the muscle lengthens.
• An isometric contraction is where the muscle is under tension but there is no visible movement.
• A motor unit consists of a motor neuron and a muscle fibre. A nerve impulse is conducted down the axon of the neuron by a nerve action potential to the neuromuscular junction.
• The all or none law determines wether is above the threshold required for the fibres in a motor unit to contract. If it is below the threshold none will contract.
• Slow oxidative muscle fibres structural features are small motor neuron size, high mitochondria density, high myoglobin content, high capillary density and low PC and glycogen stores.
• Slow oxidative muscle fibres functional features are slow contraction speed, low force produced, high fatigue resistance, high aerobic capacity and low anaerobic capacity.
• Fast oxidative muscle fibres structural characteristics are large motor neuron size, medium mitochondria density, medium myoglobin content, medium capillary density and high PC and glycogen stores.
• Fast oxidative muscle fibres functional characteristics are fast contraction speed, high force produced, medium fatigue resistance, medium aerobic capacity and high anaerobic capacity.
• Fast glycolytic muscle fibres structural characteristics are large motor neuron size, low mitochondria density, low myoglobin content, low capillary density and high PC and glycogen stores.
• Fast oxidative muscles fibres functional characteristics are fast contraction speed, high force produced, low resistance to fatigue, low aerobic capacity and very high anaerobic capacity.