Spinal Flexion: The action of bending forward, involving the movement of vertebrae closer together, primarily by the action of muscles on the anterior side of the spine.
Spinal Extension: An anatomical term that refers to the movement increasing the angle between body parts at a joint, essentially straightening from a bent position, which is predominantly performed by muscles in the erector spinae group on the posterior side of the body.
Posture: The position in which someone holds their body when standing or sitting, heavily influenced by spinal muscle activity including that of the erector spinae group