What are Movements/Joints Actions?

A movement is created by actioning muscles to act upon a joint. Elbow flexion is a joint action that decreases the elbow joint angle, think biceps curl (even though there are more muscles than the biceps involved). The opposite action is elbow extension, think triceps extensions.

To create movement, a muscle contracts to act upon a joint by pulling the other side in. Movement is always created by a pull as muscles do not push. A joint has muscles on both sides acting upon it.

The muscles that act upon the joint and create the movement are referred to as prime movers.

The other actions performed by muscles are:

  • Fixators; This is when muscles work to prevent movement in a joint or body part
  • Synergists; This is when muscles coordinate with the prime movers to stabilize and control movement
  • Antagonists; This is where the opposing muscles relax to allow the prime mover to work

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