A dynamic lumbar support located within the back of an office or home chair to enable a user to be seated close to a work surface (e.g., a desk or a table). The chair back rocks back and forth when the user shifts his weight backwards and forwards. The dynamic lumbar support includes a cushion back support manufactured from a resilient material that is responsive to a compressive force applied thereto when the user reclines and shifts his weight against the chair back. In particular, the cushion back support is adapted to change its shape from a relaxed convex shape at which to support the user's lower back and maintain a proper posture when the user sits erect and the chair back stands upright to a compressed flattened shape at which to support the user's back when he reclines and the chair back tilts backwards.