Smart Core Training Week 2 - The Curl Up

A couple weeks ago I posted the first article expanding upon a video series that we did at the Carlisle Med Gym called “Smart Core Training.” In Week 1 of the series, I highlighted the Pallof Press as a great baseline rotational core stability exercise that can build the foundation for rotary stability in real life activities, everything from opening a door to swinging a baseball bat.

Now as we move into Week 2, I’m going to share the second video that we filmed in the series, in which I demo an exercise called the Curl-Up. As you’ll see, the Curl-Up is a great exercise for building anterior core stability while also promoting spine health.

Once again, our main focus during this series is to give you some ideas for training the core for both back health and improved performance. To do this, we want to move away from the idea of training the core solely from an anatomical perspective, and instead focus on training the core from a functional perspective.

What do I mean by anatomical versus functional?

The anatomical role of a muscle is what it does when it contracts and shortens. For example, when you contract and shorten your biceps muscles, your elbows bend. Likewise, when you contract and shorten your Rectus Abdominus, your torso and spine flex forward, as in a sit-up or a crunch.

The problem with only training your muscles, in particular your core muscles, from an anatomical perspective, is that the anatomical role of a muscle really only considers what it does when it contracts concentrically, meaning when it shortens. However, muscles don’t just work concentrically, but they can also work isometrically (contracting a muscle without causing movement, as in a plank exercise), and eccentrically (contracting while simultaneously lengthening, as in a controlled lowering of a weight from the top of a biceps curl).

Viewing the training of muscles from a functional perspective requires looking at the muscles and what their primary role is in real life. For the core muscles, while they do work concentrically and eccentrically to create and control movement in the torso, their primary functional role is actually to contract isometrically to brace and buttress forces around the spine.

In this role, the core adds stability to the spine, similar to a lifting belt. It helps to decrease stress on the spine, by reducing excessive movement under tension, and by distributing the load throughout the muscles of the torso.

Training the core in congruence with its functional role of isometrically contracting to stabilize the spine against various forces is much more effective at strengthening and stabilizing the torso to function in real life and prevent low back injury.

On the other hand, if you only train the core muscles by doing things like sit-ups, crunches, or rotational sit-ups (i.e. bringing one elbow to the opposite knee in a sit-up), not only are you losing the functional benefit of training the core in a way that better transfers over to real life, but you’re also endangering the spine, particularly the intervertebral discs.

To further elucidate that point, I need to take you on a quick anatomical journey to explain how the intervertebral discs are set up and how they function. If anatomy isn’t really your thing though, don’t worry, it also involves jelly donuts – I’ll explain in a minute.

The intervertebral discs, as the name implies are discs between each vertebra of the spine. These crucial structures function as shock absorbers and ligaments to provide cushioning and hold the vertebrae together, while also allowing movement of the spine in all different planes of motion. It’s not an exaggeration to say that most of what goes wrong with the spine has something to do with these guys.

The structure of these discs is unique, and it enables them to perform the unique functions of both allowing spinal movement while also absorbing shock and impact to the spinal column. Each disc is made up of an outer fibrous ring of cartilage known as the annulus fibrosis. This outer ring is a sturdy tire-like structure which encases a gel-like center known as the nucleus pulposus.

The disc, then, is really quite similar in many ways to a jelly donut (see, I told you jelly donuts would come up!). The nucleus pulposus is akin to the jelly in the center of the donut, while the annulus fibrosis is the outer layer of donut that encases the jelly.

When talking about spine health and spine injury, problems generally arise when the donut (annulus fibrosis) encasing the jelly (nucleus pulposus) starts to break down and the jelly begins to escape. Most often this happens in a posterior direction, meaning that the jelly begins to get squeezed out of the disc toward the back of the spine and ultimately can wind up impinging the nerves that run out from the spinal column to the rest of the body.

This is the scenario in which you get things like muscle spasms in the back and nerve pain running out from the spine and down the legs. All this, because your jelly didn’t stay inside the donut….

When the jelly moves all the way outside of the donut, it is known as a disc herniation. If the jelly only starts to protrude out into the outer layers, but hasn’t fully escaped yet, it is called a disc bulge.

Now, while there are a variety of ways to cause a bulging or herniated disc, the primary mechanism is loaded flexion of the spine, especially if there is also some rotation. Think about picking up a heavy box with your back rounded, or even worse, picking up a heavy box while rotating to one side with a rounded back! That’s a terrific way to work your way towards a herniated disc!

On the other hand, performing repetitive or long duration tasks in a flexed position, like sitting or repeatedly bending over and rounding the spine can also lead to a similar result as the one-time event of picking up something heavy with poor posture.

So, both high load/low volume things like picking up a heavy box with a rounded back, and low load/high volume things like sitting with a rounded back are mechanisms that can lead to disc problems. But do you want to know an even more direct route to injuring your discs? Try doing something that is both a high load AND high volume activity….enter the sit-up exercise.

While people don’t often think of sit-ups or other similar exercises as putting a high load on the spine, research has actually discovered that sit-ups cause a large amount of compression on the spine while simultaneously moving it through flexion.

According to Dr. Stuart McGill in his book, Low Back Disorders: “The traditional sit-up imposes approximately 3300 N of compression on the spine…The National Institute of Occupational Safety and Health (NIOSH) has set the action limit for low back compression at 3300 N; repetitive loading above this level is linked with higher injury rates in workers, yet this is imposed on the spine with each repetition of the sit-up!”

What do you think happens, then, when someone does 50, 100, 500+ sit-ups a day? Not good things!

Dr. McGill also dispels the myth that sit-ups protect the low back by strengthening the core, and says that sit-ups actually create so much compression on the lumbar spine that “they ensure the person remains a patient” with low back pain.

So, how do we strengthen the core to stabilize and protect the spine? Simple, we perform an alternative exercise which has been demonstrated by the research to adequately train the abdominal muscles while not imposing excessive compression on the lumbar spine. Enter, the Curl-Up:

To summarize the Curl-Up:

What is it?

The curl-up can be very effective at building anterior core stability by training the core muscles on the front of the body. This allows us to train the Rectus Abdominus, and to a certain extent the Obliques, and the Transverse Abdominus muscles to provide spine stability without compromising low back health.

All off these muscles work together to provide stability, particularly against extension forces which try to drive the spine backwards into an arched back position.

How much?

I like to use the curl-up as a way to not only develop strength, but also to develop endurance in the abdominal muscles. To do this, I usually perform repeated 5-10 sec hold, similar to the Pallof Press. This short-duration hold ensures that proper technique is not compromised, but begins to build endurance and strength in the core.

Begin with 1-2 sets of 5 reps with 2-5 second holds, and progress all the way to 2-3 sets of 8-10 reps with 10 second holds.

How often?

Similar to the Pallof Press in week 1, the curl-up is a great baseline core stability exercise and can be used in conjunction with other core exercises like the Pallof Press in each workout of the week. As you advance further into your core training, having at least one anterior core exercise, like the curl-up, per week is ideal.