The elbow is a hinge type joint, so it will flex and extend with minimal rotation.
exstend
The flex
Voluntary muscles can be flexed.
The muscle doesn't lengthen to exert a force. There is actually a muscle on the other side of the bone, that is contracting, exerting the force. Example, most everyone knows of the Bicep (the big muscle on the your arm that guys like to flex for the ladies). Well, the tricep is on the other side (on the back of your arm, connecting to the elbow) and that muscle contracts in order to extend your arm outwards.
The Biceps flex the elbow The Triceps extend the elbow
triceps brachii
The function of the biceps brachii is to flex your arm at the elbow. However, even though that is the most visible muscle, the brachialis muscle is considered the prime mover in flexing at the elbow.
The elbow is a hinge type joint, so it will flex and extend with minimal rotation.
It either expands or contracts depending on which way you're bending your elbow.
None. Muscles only contracts. In order to extend, the muscle on the opposite movement has to contract. For example, the biceps help flex the elbow, but it does not extend the elbow; the triceps does that.
extensorThe triceps brachii is an extensor. It is the large muscle on the back of the arm and is primarily the muscle used for extension of the elbow joint or straightening of the arm. The triceps is also an antagonist of the biceps and the brachialis muscles.ExtensorsTriceps is not a flexor. It is extensor of the elbow joint.
The brachioradialis is a muscle found in the forearm that helps flex the forearm at the elbow. It is capable of pronation and supination.
flex the elbow
The bicep is a muscle on the upper arm that is designed to rotate the forearm and flex the elbow. See link below for more information.
exstend
It's easier to flex the right elbow when your forearm is supinated because the palm is turned upward.