Synergists - muscles working together

Vertebral Column

Flexion

          Rectus abdominis
          External obliqaue (bilaterally)
          Internal oblique (bilaterally)

Extension

          Spinalis (bilaterally)
          Longissimus (bilaterally)
          Lliocostalis (bilaterally)
          Multifidi (bilaterallY)
          Rotatores (bilaterally)
          Semispinalis capitis
          Quadratus lumborum (assists)
          Inertransversarii (bilaterally)
          Interspinalis
          Lattissimus dorsi (when arm is fixed)

Rotation (all unilaterally)

          Multifidi (to the opposite side)
          Rotatores (to the opposite side)
          External oblique (to the opposite side)
          Internal oblique (to the same side)

Lateral Flexion (unilaterally to the same side)

          Spinalis
          Longissimus
          Lliocostalis
          Quadratus lumborum
          External oblique
          Internal oblique
          Intertransversarii
          Latissimus dorsi