Why I Only Train My Core Isometrically, and Why You Should Too

My friend Michael was nice enough to write a guest post for me this week! Michael is a competitive weightlifter who has been performing the olympic lifts for a little over 2.5 years. He recently obtained his Honors Bachelors of Science in Kinesiology and plans to go on to complete a degree in Physiotherapy. He has gathered a lot of hands on experience working in a physiotherapy clinic for the last five years and is passionate about human strength and performance. In his spare time, he enjoys long walks on the beach and romantic comedies.

I only train my core isometrically. Without movement. No sit-ups, no side bends, no toes-to-bars, no Russian twists, none of that. I do this for two reasons: safety and functionality.

Safety

Firstly let’s look at the spine. It is made up of a series of bony vertebrae with vertebral disks in between them. Vertebral disks are made of two parts, the outer, solid layer called the Annulus Fibrosis, and the inner, viscous layer called the Nucleus pulposus. A herniation occurs when the inner layer pushes its way out through the outer layer, often (very painfully) impinging a nerve coming off the spinal cord. I don’t need to tell you that as an athlete, you don’t want this. No one does. If you do herniate a disk and it hits a nerve root, you’re looking at a lot of pain, rehab, and potentially months off of your sport.

Core exercises that involve movement of the spine increase your chances of suffering a disk herniation. Research shows that repeated spinal flexion (bending forward) is needed to cause disk herniations [1][2]. If a researcher wants to herniate a spine specimen, they will put it through thousands of cycles of flexion and extension with moderate compression. That is exactly what you are putting your spine through every time you do a sit-up or a poorly executed back extension on a GHD (compression in this case is caused by your own core muscles, think of each vertebrae as a book stacked on top of another, your muscles squeeze down on the stack of books to keep them from falling over). Why would you put your spine through that? There are several safer, more effective alternatives to train these muscles.
Research also shows that repeated twisting also makes you more vulnerable to a herniation by slowly wearing away at layers of the annulus fibrosis, making it easier for the nucleus pulposus to herniate [3]. Sure, Russian twists are working your obliques, but at what cost?

The human spine is very good at absorbing compressive forces, the vertebrae--disks and vertebral curves all allow for this. The spine is not, however, nearly as good at handling forces like shear. For example NIOSH, a health and safety board recommends a spinal compression force of no higher than 3400N during work tasks, while the limit for shear forces is only 1000N [4]. The exact numbers are not important, but safety experts agree that our spines are about 3.5 times better at handling compression than they are shear. Excessive shear becomes a problem when the spine is fully flexed forward[5] (think sit-ups, toes-to-bars, etc). These exercises definitely do a good job of working your rectus abdominus, but not without introducing potentially dangerous and unnecessary shear forces on your lumbar spine. Exercises that keep the spine in neutral or near neutral are safer because they put the spine in a position to handle forces compressively instead of introducing shear forces.

At this point is when someone would usually say something along the lines of “Well I do exercises X and my back is fine! This can’t be true.” Your back may be fine if you’re doing these exercises now, but it may not be in the future. You may be fine in the future too even if you continue to do these exercises, but you are definitely increasing your risk by continuing to do so. To succeed in any sport, you need to stay healthy. There is no reason to put your spine through potentially dangerous exercises when safer alternatives exist (more on these alternatives later). Also, you should keep in mind that the absence of pain does not mean the absence of injury. Only the outer layers of the annulus fibrosis contain sensory nerve fibers [6], so during the early stages of a herniation, pain would not be an issue.

Functionality

Almost every sport I can think of requires a core that is neutral or near neutral (don’t think of neutral as a perfect position, think of it as a certain small range of motion around that position), and a core that is braced isometrically. The only example I can think of where this isn’t true is gymnastics (but gymnasts are freaks of nature, so let’s ignore them) and maybe swimming or rowing. I’m sure there are more, but that doesn’t really matter. Most sports require a neutral, isometrically braced spine.

This is especially true of strength sports. The squat, Snatch, and Clean & Jerk all require a neutral spine that is braced isometrically. Those who bench with an arch won’t have a neutral spine and some deadilfters prefer pulling with their spine in a little bit of flexion, but both of these exercises definitely require the spine to be braced isometrically. If strength athletes always need isometric core strength, the majority of their core training should be isometric as well. Since the spine is capable of moving in three different planes, the core should be trained isometrically resisting motion in all three of these planes. You should select exercises that resist flexion and extension (bending forward and backwards), lateral flexion (bending to either side) and rotation (twisting). Below is a list of exercises that I have had good success with implementing in my training, that challenge the core in all three planes of motion. Assuming you have the basic stability needed to do them, these exercises are a solid foundation.

Here are some of my favorites!

1. Planks (resisting extension)
2. Reverse Planks (resisting flexion)
3. Side Planks (resisting lateral flexion)
4. Hollow holds (resisting lumbar extension)
5. Side hollow hold (resisting rotation)
6. Back extension holds (resisting flexion)
7. Kneeling 1 arm press (resisting rotation)
8. OH barbell spins (this is a bit all of them, but mostly resisting rotation)
1. No video for this one, but you basically hold a barbell over your head, keep your core tight and move turn your feet until you do a full 360
9. Farmer’s walks or single arm dumbell carry (resisting lateral flexion)
10. Ab Wheel (resisting at the bottom)

This list if by no means exhaustive. Get creative and find what works for you.

At the end of the day, you can train your core muscles in whatever way you want to train them. Just be aware of the risks and rewards that come with your choice of exercises and take this information into consideration before your next core workout; it’s probably not worth it. Stay safe!


Works Cited:

1. ADAMS, M A, and W C HUTTON. 'Prolapsed Interverfebral Disc'. Spine 7.3 (1982): 184-191. Web.
2. Amrani, Jacob. 'Disc Tear (Annular Tear) | Spine Doctor'. Spine Doctor. N.p., 2015. Web. 21 Aug. 2015.
3. Arjmand, Navid et al. 'Revised NIOSH Lifting Equation May Generate Spine Loads Exceeding Recommended Limits'. International Journal of Industrial Ergonomics 47 (2015): 1-8. Web.
4. Callaghan, Jack P, and Stuart M McGill. 'Intervertebral Disc Herniation: Studies On A Porcine Model Exposed To Highly Repetitive Flexion/Extension Motion With Compressive Force'. Clinical Biomechanics 16.1 (2001): 28-37. Web.
5. Drake, Janessa D.M. et al. 'The Influence Of Static Axial Torque In Combined Loading On Intervertebral Joint Failure Mechanics Using A Porcine Model'. Clinical Biomechanics 20.10 (2005): 1038-1045. Web.
6. McGill, Stuart et al. 'Shear Happens! Suggested Guidelines For Ergonomists To Reduce The Risk Of Low Back Injury From Shear Loading'. 1998. Presentation.