Exercise Analysis - Spinal Extensions

In the last two installments, I focused on basic exercises that can be used to target the predominant muscle of the abdomen. The important message was that the rectus abdominis is directly trained only when its tension development causes the spine to flex (curl forward) against opposition. Many exercisers don’t realize this and simply maintain a neutral spine while rotating their hips on a fixed thigh (or vice versa) in an attempt to target abdominals. This movement would directly work the hip flexors and only involve stabilizing isometric action by the abs.

Unfortunately, many individuals who miss the mark when (not) training abdominals in this manner do flex their spine, but only when they shouldn’t. And that would be whenever they aren’t training abs! Gravity is the culprit as its downward pull causes the spine to curl forward whenever we are standing, sitting or bending forward. If we don’t resist this pull, the C-shaped posture will prevail.

The only time we should curl our spine forward is when we are performing abdominal exercises. The rest of the time, this alignment is postural public enemy number one because it causes uneven stress on discs that are positioned between our spine’s bony segments. A disc’s outer ring dries out with aging, so there is a good chance that uneven stress will eventually manifest in protrusion of its inner matter, a condition that can wreak havoc on nearby nerve roots.

Discs are stressed the least when the spine is held in its neutral (S-shaped) alignment, so maintaining this stature 24-7 is paramount. This requires a two-pronged approach. As any nagging mom will attest, you have to remember to “stand up straight!” In other words, if you allow yourself to get in the habit of slouching, it will become status quo. But there is another important aspect of good posture that moms typically forget to mention. If less effort is required to keep your spine in line, it will be much easier to avoid falling into bad habits.

In addition to appearance enhancement and injury prevention, there is another benefit associated with building muscular strength with resistance exercise. Unlike in the gym where you increase the weight you lift when you get stronger, activities of daily living do not become progressively harder as your muscular capacity improves. In other words, in the “real” world, if you are taking out the garbage or lifting groceries, the weight of these entities remains unchanged, no matter how strong you become. This means the relative stress associated with all of your daily physical tasks is reduced when your strength improves. And one of these tasks is the maintenance of proper spinal alignment.

The take-home message is that the good-posture habit is much easier to maintain when muscles that support the effort are aboard for the ride. Therefore, to resist the pull of gravity and keep the spine from curling forward, the muscles that extend the spine (erector spinae) should be trained. These muscles oppose the motion initiated by the abdominals, so giving them attention is also important for avoiding asymmetrical development.

Curling the spine rearward against opposition will develop the erector spinae. There are two general ways to do this. One is to stand with a barbell hanging at arms length in front of you and bend forward, allowing your spine to curl down slowly in response to gravity’s pull. Once your torso is parallel to the ground, you would straighten back up, curling your spine completely to the rear as you return to an upright stature. This is called a stiff-legged deadlift.

The second way to work your erector spinae is to perform the movement described above with your legs parallel (as opposed to perpendicular) to the ground. These are called hyperextensions and are typically done on a bench designed specifically for this purpose. There are two advantages associated with spinal extensions performed in this manner. First off, the relative load you must bear is reduced when you are hanging straight down (the spine is flexed) because the lever arm associated with the weight of your upper body (and any additional weight you are holding) is minimal. Consequently, injury risk at this vulnerable position is reduced. Conversely, as you approach full extension, the load is maximal. Soft tissue of the lower back is least susceptible at this point, so an increased load would not be as dangerous and would also ensure a maximal training effect at this important peak contraction point.

As described above, hyperextensions are a compound movement because rotation of the hips on the thigh occurs in addition to spinal extension. This means the hip extensors (hamstrings and glutes) are also active as prime movers. This is not problematic because these muscles are typically stronger than the erector spinae, so their premature fatigue would not be expected to preclude effective erector training. However, this involvement must be taken into consideration when organizing your training schedule. If you split muscle groups over multiple sessions, it’s important to perform hyperextensions either with hip extensor work (leg presses, squats and leg curls) or outside of a 48-hour window that will allow for sufficient recuperation of muscle groups that are common to both workouts. 

This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.





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