Sold by various fitness equipment manufacturers, the back extension bench is a piece of fitness equipment that is designed to strengthen the muscles of the lower back. It is found in most health clubs and fitness centers and is typically located near the abdominal machines and free-weight equipment. Though the back extension bench is largely intended to train the back muscles, it can also be used to work the backs of the legs and the sides of the torso, depending on how one is positioned on the bench.
Back extension can be defined as the straightening of the spine from a forward-curled position, and it is not to be confused with back hyperextension, which is the arching of the back. It occurs in the thoracic region of the spine as the vertebrae pull away from each other, and the primary muscle responsible for back extension is the erector spinae muscle. Technically a bundle of smaller muscles, the erector spinae runs vertically along the middle of the back from the cervical vertebrae all the way to the sacrum, which is found at the bottom of the spinal column just above the hip bone.
While the back extension bench, alternately known as the Roman chair or the 45-degree back extension bench, indeed works the back extensor muscles, back extension on this equipment is accompanied by hip extension, or the straightening of the hip joint. Muscles involved in hip extension include the glutes and hamstrings; therefore these muscles are also worked when using the back extension bench. The degree of involvement of the leg muscles depends on the design of the bench and the position of the body during the exercise.
Typically, the bench incorporates an angled bar with hip pads at the top and calf pads at the bottom to hold the backs of the legs in place. To use the bench, the exerciser positions himself face down on a 45-degree incline, so that he is leaning forward with his legs pinned under the calf pads. He would then bend forward at the hips and spine to lower his torso and head toward the floor, and then contract the lower back muscles to extend his spine and hips until he lifts his body back into a straight line. To put more emphasis on the backs of the legs, he would bend forward from the hips only, keeping his back straight, and then contract the glutes and hamstrings to lift himself back up.