Your core muscles are actually composed of several major muscle groups including:
Transverse Abdominis (TVA) The deepest of the abdominal muscles, this core muscle lies under the obliques (muscles of your waist). It acts like a weight belt, wrapping around your spine for protection and stability.
Multifidus Muscle The Multifidus Muscle is a thin, yet stiff, core muscle deep in the spine. It stabilizes each joint, makes each vertebra work more effectively, and reduces the degeneration of the joint structures.
External Obliques These core muscles are on the side and front of the abdomen, around your waist, and lays on top of the internal obliques.
Internal Obliques These core muscles lie under the external obliques, running in the opposite direction.
Rectus Abdominis The Rectus Abdominis is a long muscle that extends along the front of the abdomen. This is the 'six-pack' part that becomes visible with reduced body fat.
Erector Spinae The erector spinae is a collection of three core muscles along your neck to your lower back.