Muscles that assist the prime mover in performing a joint action. That is, all muscles that can perform a joint action that are not the prime mover, are termed synergists. Example: The rectus abdominis is the prime mover of spinal flexion. All other muscles that can perform spinal flexion are synergists including – external obliques, internal obliques and psoas.

Related Terms

  • Agonist
  • Antagonist
  • Fixator
  • Motor unit
  • Muscle fiber


  • assistor
  • Synergist