Back Extension

The back extension machine is a resistance exercise machine, which is designed to target the spinal erectors. This exercise is performed in a seated position with the upper back pushing backward against a cylindrical pad.

The concentric portion of the lift is hip extension as the upper back pushes backward against the resistance. The eccentric portion is hip flexion as the torso bends forward at the hip joint to return to starting position.

The purpose of the back extension machine is to strengthen the muscles that erect the spine (i.e. erector spinae) while also promoting the hypertrophy (increases in size) of this muscle group. The machine, however, comes with great risk of injury and is a relatively ineffective machine when comparing benefits that do not outweigh the risks.

The back extension machine is designed to strengthen and develop the erector spinae muscle group, however, it is not recommended. The resistance bar, that is located across the upper back, can compromise the safety of the lifter as the lifter flexes the hips forward during the descent of the weight. The limited range of motion of the back extension machine not only makes the exercise ineffective, but also compromises the safety of the lifter.

The erector spinae muscle group is located at the on the back extending from the pelvis to the skull and cervical vertebrae. The iliocostalis is the most lateral of the erector spinae muscle group, extending from the pelvis to the neck. Its origin is located at the iliac crest of the pelvis, the inferior 6 ribs, and ribs 3 to 6. Its insertion is located along the angles of the lower and middle ribs and the transverse processes of cervical vertebrae C6-C4. The iliocostalis extends the vertebral column and maintains erect posture.

The longissimus extends from the lumbar region to the skull and primarily passes through the transverse processes of the vertebrae. Its origin is located at the transverse process of the lumbar region continuing upward through cervical vertebrae. Its insertion is located at the transverse processes of the thoracic and cervical vertebrae and the ribs. The capitis part of the longissimus muscle inserts into the mastoid process of the temporal bone of the skull. The longissimus extends the vertebral column and head.

The spinalis is the most medial of the erector spinae muscle group. Its origin is located at the spines of upper lumbar and lower thoracic vertebrae. Its insertion is located at the spines of the upper thoracic and cervical vertebrae. The spinalis extends the vertebral column.

The semispinalis extends from the thoracic region to the head. Its origin is located at the transverse processes of C7 to T12. Its insertion is located at the occipital bone (on the back of the skull) and spinous process of cervical and thoracic vertebrae. The semispinalis extends the vertebral column and is a synergist of the sternocleidomastoid. 

The quadratus lumborum forms the posterior part of the abdominal wall. Its origin is located at the iliac crest of the pelvis and lumbar fascia. Its insertion is located at the transverse processes of the upper lumbar vertebrae and lower margin of the 12th rib. The quadratus lumborum extends the lumbar region of the spine.

Although lateral and rotational movements of the spine are completely omitted from this exercise, the oblique muscles contribute to spinal extension in this exercise. The abdominal wall is made up of broad, flat sheet-like muscles that are layered. The oblique muscles are essential to trunk rotation and lateral flexion of the vertebral column (as with oblique crunches). They surround the rectus abdominis on both sides. The external oblique muscle runs downward and medially and forms the inguinal ligament of the groin area. Its origin is at the outer surfaces of the lower eight ribs and it inserts into the linea alba via a broad aponeurosis. Some of the fibers of the external oblique insert into the pubic crest and iliac crest.

The internal oblique, as its name suggests, is located below the superficial external oblique. Its fibers run in an upward and medial direction. Its origin is located at lumbar fascia, iliac crest and inguinal ligament. Its insertion is located at the linea alba, the pubic crest and the last three or four ribs.

The rhomboids and middle trapezius play an important role in stabilizing the upper back with scapula retracted while the torso is maintained erect. This prevents rounding of the shoulders throughout the exercise.

The piriformis, obturator externus, obturator internus, gemellus, quadratus femoris play an important role in stabilizing the hip joint while the transverse abdominis helps stabilize the torso.

Good mornings, supermans, hyperextensions.

Focus on the concentric portion of the contraction, concentrating on “squeezing” as the body pushes the cylindrical pad/bar backward.

Perform other exercises to effectively strengthen the back without the increased risk of back injury associated with the back extension machine. Exercises such as good mornings, superman variations, and hyperextensions are more effective and come with less risk of back injury. (It is important to note that good mornings are an advanced exercise.)

It’s important to note that your repetition and set volume will depend on your goals (e.g. strength, hypertrophy, muscular endurance). It is also important to allow adequate recovery days in between back and leg training days to allow muscles to repair.

Using momentum to push the resistance backward minimizes the potential of force production of the erector spinae muscles. Furthermore, using momentum can increase the risk for lower back injury. It is important that both the eccentric and concentric phases of the exercise are controlled.

Flexing the torso excessively at the bottom on the eccentric phase (as the hips are bending forward) may cause injury to lower back if the resistance cannot be controlled and the starting position is not set correctly.

Rounding the back can minimize force production and increase the risk of injury. It’s important to maintain the back straight as the hip flexes and extends.

Executing this exercise with heavy weight can be hazardous to the lifter. It is important that the lifter perform this exercise with a light weight to prevent injury.

If the lifter has a compromised range of motion with the back or hamstrings and/or performs this exercise incorrectly, this exercise can increase the risk of injury and/or exacerbate a previous injury.

If proper technique and recovery are not adhered to, injury to the lower back and/or hamstrings may occur.