You know the drill: crunches, leg extensions, barbell rollouts, chops, planks, twists, rows, sit-ups, and deadlifts. All those exercises move you toward a goal of washboard abs. But well-defined abs aren’t the same as having a strong core.
Your “core” is really a group of muscles in your lower back, stomach and hips. Basically, all the muscles you have that are not in your arms and legs. Their function is to keep the spine stable and the body upright. They help bending, rotation, and twisting and are involved in just about every moment you do.