McGill Big 3 and Low Back Pain

You’ll see many social media posts and blogs mention the McGill ratios/McGill endurance test/McGill big 3. These tests are an approach to causes of low back pain (LBP) and muscular imbalance or weakness, let’s have a look at what they involve. These test core stiffness and endurance of the core or trunk muscles, we use these when we sit, walk, sun, squat…you get the picture, pretty much when we move.

As with everything there has recently been some contention and controversy around this, what if your too stiff from LBP and actually needing some mobility and addressing some fear-based guarding and protective movement? Some people will benefit greatly from this while others may not, it’s all about context.

What is the McGill Big 3?

This protocol consists of three tests that measure aspects of torso strength and endurance. They’re timed in a static, isometric (muscle contraction without a change in length) contraction of the muscles that stabilise the trunk until fatigue.

These should all be done with a health professional as some conditions may not be suitable to perform them.

1. Trunk flexor test

Used to assess anterior abdominal muscles, think rectus abdominis or ‘6 pack’.

To test at home start in a seated upright position angled at 60 degrees from the floor. Both knees and hips are flexed 90 degrees, the arms are folded across the chest with the hands placed on the opposite shoulder while feet are secured with something. This position is held as an isometric posture for as long as possible until failure. Stop if you have LBP.

2. Trunk extensor test

Used to assess erector spinae and multifidus, these are our posterior superior and deep back muscles.

Most people do not like doing this one and not suggested to try at home. This test requires you to be essentially hanging off the end of a test bench with pelvis, knees and hips secured, arms are across the chest. Ensuring correct alignment from the practitioner, hold until failure which is when the upper body drops past the horizontal position. Stop if you have LBP.

The bird dog position can also be used to test this.

3. Left & Right lateral muscle test.

Used to assess obliques, transverse abdominis and QL.

Lay in a full side plank position with top foot placed in front of the lower foot for support. The upper body is supported with the elbow and forearm on the floor and create a straight line from head to toe with top arm across chest. Hold until failure, which is loss of straight-backed posture or hips drop to the ground. Test the other side. Stop if you have LBP.

Interpreting Results

We interpret these with ratio comparisons between muscle groups.

• Flexion and extension ratio should be less than 1.
• Right and left side plank ratio should be no greater then 0.05 from a balanced score of 1.
• Side plank and extension ratio should be less than 0.75.

What now?

While a test like this give practitioners an indication of muscular imbalances, there is no single muscle or single exercise for low back pain. Come in for a full assessment and a plan personal to you!

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