B3 - Antagonist muscle pairs

• a pair of muscles that work together in order to create movement • one contracts while the other relaxes in order to create movement

• muscles that work together to enable the agonist to operate more effectively

• muscles that help stabilise the joints around the origin of the movement

• one end of the muscle that remains stationary

• the moving end of the muscle

• muscle fibres work on an ‘all or nothing’ basis • this means within the muscle groups of motor units, the all or nothing rule applies to these, not each individual muscle fibre within the muscle

• on end of the muscle remains stationary (if it is an isolated movement), known as the origin • the moving end of the muscle is known as the insertion

• muscles work in pairs (or even groups) • if one muscle were to contract, no movement would occur unless there is relaxation from another

• ‘partial contraction’ • this is preparation to react to a stimulus from your nervous system

• muscles cross over joints

• muscle can only ever pull • they can contract without shortening to hold a joint firm fixed in a certain position • but to allow movement they only pull on a bone

• when the contraction ends, muscles relax (go soft) but no movement occurs until its antagonist partner contracts to bring the movement back

• the muscle that contracts and shortens

• the muscle that relaxes and lengthens

• movement cannot occur without the antagonist relaxing, the antagonist also acts as a ‘brake’ and controls the movement speed

• they help control the direction of pull from the agonist and also help develop force for the movement (meaning all the force isn’t necessarily created by the agonist)

• they contract in order to reduce any un-wanted movement from the origin, meaning the agonist is more effective

agonist - bicep brachii antagonist - tricep brachii fixator - deltoid synergists - brachioradialis