Posted January 8, 2014

Spinal Flexion is Important for Low Back Health and Strength

The pendulum in fitness tends to swing both ways, and it tends to go pretty far depending on how many people are pushing and how hard they’re making a case. For instance, spinal flexion has gone through the gamut, from training the core with flexion based crunches to crunches are the devil and any time the spine bends in a forward manner is like bending a credit card and will make your discs herniate and cause instant death.

Sure, there’s research showing that spinal flexion under load is a major predicator to injury, especially if there’s shear forces or torque applied to the spine when in a flexed position, and much of the research is coming from Dr. Stuart McGill, whose work I reference quite a bit. The forces acting on the spine increase by up to 10-15 times by simply flexing the lumbar spine, which could mean a small weight could surpass the tissues strain tolerance and lead to mechanical failure, otherwise classified as an owie.

When in a flexed state the active support network of the erector spinae muscles, multifidus, latissimus dorsi, and quadratus lumborum are in a stretched position, which reduces their ability to produce force to resist further deformation of the spine. This can increase the risk of the spine being moved into a position that it can’t tolerate well, spraining a ligament or fascial tissue and potentially lead into more pain than a turtle slap fight.


An often forgotten part of spinal research is simply looking at the available range of motion available to the spine. The lumbar spine has a great propensity to flex and extend, with up to 14 degrees of movement available per vertebral segment in the lower sections. This means there’s inherrent mobility in flexion that if not trained could be lost.

There’s a tremendous range of motion available to the spine, and to avoid using it would be analagous to not move other body parts through their full range of motion. Would you want to walk around with a knee that doesn’t straighten all the way out, or move a shoulder that doesn’t get over the height of your collarbone? Even if the risk of ACL injuries are higher when the knee is locked out, and the risk of rotator cuff impingement and tear is higher when the subacromial space is compressed when in an overhead position?

A big component of the spinal flexion debate that is often misplaced is the role of loading during flexion. If you were to simply slump at your computer screen, the load on the low back wouldn’t be too great. Sure, it would take a toll if you stayed there for an extended period of time, like 8 hours a day, 5 days a week for the next 20 years, but to simply slump once won’t kill you. We’d be pretty poorly designed creature if all it took was a simple flexion to break us down.

In this instance, the direction of loading is axial, which means straight down from the top of your head through your hips. If we added weight to your build, your low back would feel it, but the overall stress to the low back would be less than compared to shear loading, which is when the direction of loading is at more of a horizontal angle to the spine, like if you were to lean forward and grab a heavy weight off the floor, like this guy.

Basic pythagoreams’ theorem (that’s math, yo) shows that the further an axis of rotation – in this case the vertebrae of the low back – is from the base of support, the greater the rotational forces acting on it. When the spine is in flexion, it actually increases the relative distance of the axis of rotation to the base of support, which increases the force on the area even with the exact same load.

On top of this, for mundane and low load tasks, involving a small amount of spinal flexion to bend and pick up stuff is more energectially efficient than using the hips or knees, which means less work is needed. In a fitness context, this is complete blasphemy, but in a developmental context, using less energy for mundane activities leads more energy for learning, growing, fight or flight (if needed), and mating in order to perpetuate the species.

I’ll bet when you tuned in today you didn’t think you’d get a monitor full of talk about math, evolution, mating, and turtle-slaps, did you??

So when your spine is in flexion, it’s more susceptible to injury as the force acting on the back is magnified, especially if the spine is in a position where shear forces can act on it. For this reason, deadlifting with a flexed spine is a bad ideal, as is lifting any appreciably heavy weight with a flexed spine. But as said, flexion is a natural and important characteristic of the spine, which means it has to be involved in order to be maintained. Much in the same way that hip mobility has to be maintained in order to still be able to play golf when you’re 80 and chase after the nurses in the nursing home, but loading a movement like this with a metric tonne of weight would not go too well.

Imagine if you walked into the gym tomorrow and saw someone who had heard from someone who had read this article that I said you should all do heavy weighted squats like that? That’s how fitness rumours get started. It’s like the childhood game of Telephone except instead of someone saying something funny at the end a little part of my soul dies and I have to go all Wayne Brady on someone in the gym.

Since spinal flexion is important to train but you shouldn’t do it with heavy loading and shear forces, how do you effectively get to train it? Well, start by not using max loads through a compromising range of motion, and try using some low to no resistance movements.

Once you can get the range of motion with minimal loading, you can add in a couple of variables to challenge the control of the movement, like speed, instability, and variability of the surface.

From there add in some loading within the tolerances of the spine.

Just do me a favour and don’t try to rush into flexion based movements like you’re a damn yoga master or something. There’s a fine line between someone in their 50’s training to increase their ability to take spinal flexion postures without pain or dysfunction through gradual applications of small incrementally increases in challenge or stress to the spine to accommodate adaptation, and trying to tie yourself in knots. Plus, this is never a good idea, no matter how in touch with your chi it may make you:


┬áHe looks like he’s rockin a hard Ed Grimley impression. Go ahead, Google it.

So in closing, don’t fear spinal flexion, just don’t load it up. You need it to do simple thing like tie your shoes, see your shoes, get out of bed, have fun while you’re in bed, and a whole bunch of other things, so make sure you can still use it for the rest of your life. Train it, and don’t get mad at me if your discs explode when you try to do a max effort good morning with your spine at the end of its’ natural limits. Keep the loading light, son.

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