Exercises of the vertebral column have two functions: to maintain or increase flexibility; and to maintain or increase the strength of surrounding muscles.
Flexibility is effectively and safely achieved through prolonged relaxed stretching. Strengthening of vertebral muscles, in particular the abdominals, gives greater control over the spine during other activities, Appropriate strengthening exercises should be incorporated into every exercise program to safeguard against back injury.
To ensure that an exercise is safe and effective, the following questions should be asked:
what is the purpose of this exercise? Am I achieving this purpose? Could this exercise be improved? Does it unnecessarily involve the lumbar spine? Could it damage the lumbar spine?
If you answered, “I don’t know”, for any of those questions for any exercise you do, then do not do that exercise until you get advice from someone who can answer for you, You would be looking for someone who is an exercise specialist, or health professional with a degree or diploma in fitness or a related field.
There are five categories of exercise for the spine, and each one has dangers and benefits.
During flexion (bending forward when standing, sitting, or lying) pressure on the discs of the spine increases, and the disc nucleus tends to move backward to where structural strength is weaker, especially at the fourth and fifth lumbar vertebrae. These factors together greatly increase the chance of disc damage and prolapse.
If flexion is used as part of an exercise program, it must be in moderation, as well as having a definite purpose. I cringe when I see an instructor taking a class through 5, 10, 15, and even 20 minutes of endless abdominal curls, and sit-ups. If this happens in a class, I’ll just quietly lie there and do some safer and more effective exercises.
Flexion and rotation
This is a movement that combines flexion with rotation, but because of the alignment of the joints within the lumbar spine, rotation is limited between individual vertebrae. The rotation creates a very large shearing or tearing, forces across the fibers of the disc, which, if severe enough, can actually tear the disc and lead to prolapse.
Combined flexion and rotation, even more than flexion alone, greatly increases the probability, of disc-damage during exercise and should be avoided at all costs. Simply do not do some of those old popular exercises like the “windmill” or alternate toe touches. If an instructor has them in their repertoire, they should not be an instructor.
Many exercises using flexion and rotation can be modified so that they require either flexion or rotation, but not both. This is where you need to get advice from a well-educated exercise specialist, not an instructor with good intentions but not enough knowledge.
Hyperextension goes beyond the normal functioning of the vertebrae by arching your spine backward. This removes the shock-absorbing ability of the discs and puts pressure on the facet joints.
If it is done in a ballistic way with little control, it can wear out the fibers of the disc. Hyperextension also reduces the size of the space available to the spinal nerve and can predispose you to spasms of the muscles in your back, hip, or leg.
Limit the extension of your spine to the neutral position where the spine moves no further than where it would be in a normal standing position. Listen carefully to the instructions of your instructor in the gym or during a class, or modify the exercise.
Avoid hyperextension unless it can be performed as a passive movement, for example in a stretching routine, or an exercise is given by a physiotherapist.
Abdominal exercises can be done in a variety of ways, but most instructors just use those boring old abdominal curls. To protect the lumbar spine, all abdominal curls or sit-ups should begin with the knee bent to 90 degrees and with the feet flat on the floor, so that the lumbar spine is flattened.
This position also inhibits the action of the iliopsoas muscle, a hip flexor that contracts during a straight-leg or anchored-feet sit-up. This powerful muscle attaches to both sides of the entire lumbar spine and will pull the spine into hyperextension during the exercise, dramatically increasing the potential for spinal injuries.
Contracting the abdominal muscles, tilts the pelvis backward, bracing, and protecting the lumbar spine. The basic abdominal curl should begin with the head, followed by the shoulders and trunk, and end at the point where the tips of the fingers are just above the tops of the knees. This method avoids the harmful hyperextension of the vertebrae that other versions of this exercise can create.
Hip-flexor exercises such as lying front, leg raises, double leg raises, and bent knee leg raises, or knee raises on the hip flexor station at the gym, should not be included in a true abdominal exercise sequence.
Hip-flexor exercises do involve the abdominals — not as prime movers but in an isometric (equally measured) or static (stationary) contraction. This fatigues and even damages the abdominals but doesn’t make them fitter.
Double leg lifts and supine straight double leg scissors are examples of poor abdominal exercises. The lifting of the leg is mainly the result of the contraction of the iliopsoas while the abdominals contract isometrically to stabilize the pelvis as the legs are held above the ground. They tend to produce very large forces within the lumbar spine and fatigue the abdominals, leading to repeated lumbar hyperextensions and damage to the spine.