How low back muscles help protect your spine

Apr 25, 2022

I often talk about the importance of building strong and healthy muscles to protect the lower back and avoid pain and injury. But just which muscles am I talking about here and how exactly do they do their job?

Which are the key lower back muscles?

In the tutorial above I focus on two muscles – or groups of muscles – longissimus and iliocostalis, part of the erector spinae muscles, which go all the way from the tail bone up to the back of the neck.

Longissimus – this originates down on the sacrum, iliac crest and the spinus and transverse processes of the lumbar spine. These are the bony projections that stick out diagonally from the back of the vertebrae. The longissimus travels all the way up into the thoracic spine and inserts onto the ribs.

Iliocostalis – this starts down in the same area, from the sacrum, iliac crest and also the thoracolumbar fascia, like longissimus it inserts up into the thoracic spine and out onto the ribs.

As I want to concentrate on the lower back in this tutorial, we are just going to be talking about the lumbar and thoracic portions of these important long back muscles.

What is the role of the lower back muscles?

Both longissimus and iliocostalis are important in our posture. They steady the vertebral column on the pelvis as we walk and move around, helping the spine to stay erect and to maintain the correct curvature.

You might have heard of them as spinal extensors. One key role of these muscles, and the relevant one here, is helping our spine to manage the shear forces that are at play on it.

What do we mean by shear forces on the spine?

Picture what’s happening to your spinal column when you bend forwards. Without something to stop it, each vertebra would slide forwards on the one below it. The more you bend, the higher the anterior shear force you’re putting on each vertebra. That’s where your spinal extensors come into play, to counteract that shear force. As you bend forwards, the back muscles contract to create a posterior shear force that pulls the vertebrae back into place.

Of course, your vertebrae won’t fall off one another, no matter how far you bend, but if they slip forwards – as can happen in a condition called spondylolisthesis – back pain can result.  

When we move and exercise, we should be at least aware of these forces at work, maintaining a neutral posture where possible. Essentially you want to hold the spine in position so that none of the segments collapse with it and everything stays where it should be.

Lifting safely

Lifting is something we do in the gym for exercise but also during everyday life, shopping for instance, gardening or completing jobs around the house. This can put unwanted stress on the lumbar spine if we’re not careful. Try to be mindful of your back whenever you do any form of lifting. Here are three ways you can activate the spinal extensors to make sure they’re acting to counterbalance the shear force on your spine.

  1. Focus on maintaining a neutral spine – focus on this before going into a flex position. This will allow the spinal extensors to activate effectively.
  2. Brace your abdominals – these can work with the longissimus and iliocostalis to help to ‘lock’ your spine in position.
  3. Bend from the hips – Rather than flexing from the spine, put those big powerful movement muscles (the glutes) to good use, rotate from the hip and bend your knees at the end to pick up the weight.

The best exercises to work on low back muscles?

Let’s start with what not to do. People often advocate for laying on your back and lifting your chest up, creating a large arch in your spine. My advice is to avoid this as it puts too much pressure and tension on the spine by creating compression. It can also cause damage and inflammation to the facet joints that sit between the spinus processors and vertebrae.

So how best to manage forces and activate muscles?

I recommend the Bird Dog.

If you’re not familiar, come down onto all fours and stretch alternate arms and legs out (you can see the video above for a demonstrate if you’re unsure). It can take a bit of practise but is brilliant for working several core muscle groups at the same time. And in the case of the spinal erectors, it allows you to maintain a neutral posture while getting those important muscles activated and ready to protect the spine. It will also get your glutes, shoulders and lats activated at the same time. All from that one exercise.

Even better, you’ll be halving the compression you put on the spine when compared to a back bend, as you only lift the arm or leg on one side of the body at a time. Thus, the erector spinae is working only on one side at a time. This is milder in the way is stresses the spine and can make a world of difference, particularly if you already suffer with back pain.


If you’re suffering with lower back pain and feel you could do with some tailored support to help you find a solution, check out my How to Overcome lower back pain consultation and course.

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