Functional Roles of Muscles and Types of Contraction

• The agonist is the prime mover.
• The agonist is the muscle responsible for causing movement.
• The agonist normally shortens to produce movement.
• The antagonist is the muscle that works opposite the agonist to allow co-ordinated movement.
• The antagonist normally lengthens.
• The antagonist normally relaxes.
• The fixator stabilises the joint.
• The fixator often located above the antagonistic pair.
• The fixator helps the agonist function effectively.
• Isotonic contraction: tension in a muscle which changes length causing movement at a joint.
• Concentric contraction: tension develops as muscle shortens, causes joint movement.
• Eccentric contraction: tension develops as muscle lengthens, controls joint movement, occurs when working against resistance (gravity or weights).
• Isometric contraction: tension in a muscle with no movement at a joint, muscle stays the same length, stops movement.