The document discusses core stability and core muscles. The core, or lumbo-pelvic-hip complex, consists of 29 muscles including the abdominal muscles, back muscles, and hip muscles. It is the center of gravity and where all movement originates. Core training exercises like planks, bridges, and exercises using a Swiss ball can improve posture, muscle balance, stabilization, and prevent low back pain by developing efficient neuromuscular control since all movement originates from the core. Sample exercises described are planks, bridges, planks on a Swiss ball, Swiss ball curls, supermans, and more.