McGill Curl Up Exercise: Everything You Need To Know
The McGill Curl up exercise is fundamental for developing a strong and resilient core. The exercise itself is named after Dr.Stuart McGill of https://www.backfitpro.com/.
Stuart McGill has been a Professor of Spine Biomechanics for the past 30 years at the University of Waterloo, Canada, where he has a laboratory and clinic that explore low back mechanics, injury mechanisms, rehabilitation protocols, and performance enhancement.
The Curl-Up exercise is very popular with bodyworkers and strength coaches as it promotes the development of strong core stability without actively flexing and stressing the spine.
The curl-up, along with the bird-dog and side plank, form the notorious “Big 3”. These exercises when performed correctly, can dramatically reduce and prevent back pain in many individuals.
We recommend you spend some time learning how to execute this exercise correctly before adding it to a well-designed training program.
Exercise benefits include:
- Developing Core Stability
- Reduce Chronic Back Pain
- Improved Core Neuromuscular performance
- Maintain Spine Health And Function
McGill Curl Up Muscles Worked
The Curl-Up exercise was developed to train the core musculature and nervous system without having to perform a forward flexion movement. That is folding over to the front like the more traditional sit-up or crunch exercise.
That being said, you still need to be able to activate and train the muscles of the core to maintain correct spine health and performance.
The spine has many functions including bending, flexion, extension, and rotation. As if this wasn’t enough, it also has to be strong enough to withstand huge compressive forces. Think about a heavy back barbell back squat.
The spines movement relies upon a symphony of muscular concentrations pulling from multiple directions. Each contraction is timed to perfection, with its own unique degree of force as composed by the Central Nervous System.
Some of the main muscles responsible for this movement include:
- Rectus Abdominus
- Transverse Abdominus
- Internal & External Obliques
- Spinal Erectors
Not to mention the deep stability muscles thatat form the structural wireframe around the spine itself.

Spinal Flexion: Movement Vs Moment
Perhaps the main difference between the McGill Curl up and the more traditional “Ab Exercises” like the crunch is that curl-ups focus more on flexion moment rather than flexion movement.
Where exercises like the “sit-up” train the abdominal muscles through a flexion and crunch movement, the McGill curl up trains the same muscles involved without actually bending the spine.
This is referred to as a flexion moment. The stress of the muscle isometric contraction is present, but the spine itself doesn’t actually flex or move.
This will allow for the same, or greater benefits, to traditional “Ab Work” without the associated risk of straining the layers of collagen in the spinal discs.
We want to keep our spine in a neutral “Range” for this exercise.
That is lifting your shoulders, chest, head, and back just enough to activate the core. But, not so far so as to flex the spine and compromise your disc health.

The goal of training the “McGill Big 3′ is to create a solid foundation of core strength and neuromuscular performance to eventually move onto more specific exercises for improving athletic performance.
Loaded exercises such as the squat, overhead press, and deadlift will provide significant core training without actually flexing the spine.
McGill Curl Up Form in 4 Simple Steps
Step 1: The Set Up
To complete the McGill Curl Up you will need a yoga mat or bath towel.
Find a large enough area where you can remain undisturbed to focus on the correct movements. This exercise is as difficult for your head as it is for your core.
Once your mat (or towel) is ready, lie down on your back.
Step 2: Hand & Foot Position
To start, we will place our dominant foot on the floor with a bend in the knee. The opposite leg will be stretched out flat against the floor.
Once we reach the halfway point of the set we will swap our legs positions so that our dominant leg is stretched out and the non-dominant side is bent at the knee and with the foot fully on the floor.
As we lie on the floor, we will place our hands flat on the floor, underneath our lower backs. Our fingers will lie on top of each other under the spine.
This is to support the lumbar spines natural curve, we want to maintain this posture in our lower backs throughout the reps.
Step 3: Start Of The Rep
The movement is relatively shallow, but a very potent one for developing our upper abdominal muscles.
Our objective is to raise our upper back off, shoulders and head off the floor.
Only your hands should be touching the floor. Avoid using your elbows to assist with reaching the top of the rep, as you could strain your shoulders.
Begin to lift your shoulders, head, and chest off the floor simultaneously. Exhaling through your mouth as if you were trying to blow a balloon.
Hover just slightly off the floor for a few seconds before returning to the start position.
Imagine your head, shoulders and upper back are resting on a scales. Your job is to lift them off that scales just enough to set the scales to zero.
Step 4: Complete The Set
The tempo is slow and controlled to emphasize the ab muscles being used.
There is only a slight movement to get into position.
Remember, your spine is to remain neutral. Your core muscles will activate as they try and hold this position as you hover off the ground.
You can keep your chin tucked if you notice your neck muscles getting fatigued.
As with all exercises, movement quality comes before movement quantity.

A Side Note: How did you end up here?
Odds are that if you have found this exercise guide you will be suffering from some sort of back pain. You have possibly been recommended to perform the McGill Curl up as an injury recovery or even prevention exercise.
Unfortunately, the McGill curl-up isn’t as sexy as a glute kick-back, however, it is a fantastic exercise with powerful effects.
If you have been sent by a physio or coach, I want to acknowledge the fact that they recognize this exercise, Dr.McGill’s work, and especially your long term health.
Kudo’s to them, and kudos to you for taking an interest in yourself!
If you have any questions please leave a comment below.
I will do my best to answer, or find you an answer.
Regards,
Michael Shortall
Can someone definitively answer why one leg is bent and one leg is straight on the curl up?
Hello John C. Simpson.
It’s beena while since I done my deep dive on the Curl up!
However, I will try and answer best I can from a first principles perspective.
Theidea of bending the knee is to limit any additional strain or pain caused in or around the lumbar spine during the movement.
It is common enough for someone experience lower back pain to exacerbate the problem when perfomring core, or crunch exercises.
This is mostly due to a shortening, or weakness in the hip flexor muscles. Specifically the Psoas.
Which will try and contract during the curl up movement. Especially in a beginner due to poor movement control or kinisthetic awareness.
Now, as to why one leg would be bent while the other remains straight.
The Asymettrical leg position is supposed to further actiuvate the deep core muscles during the movement.
When you combine all the various reasons and remeber that the McGill Curl up is usually used with clients want to build baseline core strength while also experiencing back pain it make sense.
I hope this helps.
Kind regards,
Mike