The Best Core Exercises for Lower Back Pain

Every core routine for back pain seems to start with crunches or sit-ups. The instinct isn't wrong. Your back hurts and you hear that a strong core is important for supporting the spine. The problem is two-fold: crunches and sit-ups work the wrong muscles, and perhaps more importantly: they flex the spine.

First off, what is your "core"?

Ask most people to point at their core and they'll point at their abs. That's one muscle group. The whole thing is better described as a cylinder containing: rectus abdominis and the obliques across the front and sides, the erector spinae and deep spinal muscles on the back, your diaphragm as the lid and your pelvic floor as the base. And many others contribute as well like your latissimus dorsi (lats) and your quadratus lumborum (QL).

Its job through a normal day isn't to bend you. It's to hold your spine steady while your arms and legs propel you through space and do things. Carrying a car seat. Reaching to the back of the fridge. All the boring stuff.

A crunch trains your core to bend your spine purposefully. This isn’t inherently a problem for people. However, when suffering from intense back pain, there’s sound logic and evidence to support avoiding repeated spinal flexion, at least until the pain calms down. Nearly everything the research calls "stabilization exercise" tries to hold your core still against a force, and for good reason.

Why repeated bending is a poor bet

Ah yes, back to my jelly-filled onion analogy. This one just won’t die. Your disc is layers of tough collagen rings, the annulus, wrapped around a gel centre, the nucleus. Bend forward and the front squashes while the back stretches in tension, which nudges that gel backwards into the rings. Once, nothing happens. The disc springs back. No problem.

Thousands of times under load is a different story. One study loaded pig spine segments into a rig and cycled them through flexion and extension, up to 86,400 cycles, under a modest compressive force [1]. Herniations appeared at the back and back corner of the disc, the same places they’re found inside people.

Now the honest caveat. Those were pig spines in a machine, and nobody is doing 86,400 crunches. I spent my PhD on disc mechanics and the gap between a loading rig and a person on a yoga mat is real. So let me be clear. A set of crunches won’t make your sore back explode. The point is that repeated loaded flexion, like with sit-ups and crunches, is a pattern of movement that can exacerbate an already sore back. So if your back already hurts when you bend, building a routine around bending is a strange place to start. Stop poking the bear.

In living humans the closest look is an old EMG study. Nine volunteers ran through 12 abdominal exercises while researchers measured how hard the abs worked and how much spine compression it cost [2]. Partial curl-ups gave the best muscle challenge per unit of spine load. As a biomechanist, I read that as good news. The abdominal work isn't the problem, the deep repeated bending is, and that means you can get the stimulus without the flaws.

What to do this week

The core exercises with the best evidence behind them for lower back pain are endurance holds, not high-rep sit-ups. Side planks, front planks, bird dogs, dead bugs. You could try throwing in the exercise mentioned in a recent newsletter: the reverse plank.

1. Pick a couple exercises. The McGill Big 3 are the standard set: the modified curl-up, the side plank, the bird dog. Guide here: https://squatuniversity.com/2018/06/21/the-mcgill-big-3-for-core-stability/
2. 2 sets per exercise (2 for each side with the side planks), 2-3 times per week. Start with short holds and work your way up.
3. Add time before you switch to more difficult variations.
4. If pain goes above 4/10 during a hold, or you're noticeably worse the next morning, scale it back. Keep moving and walking, then try again with an easier variation.

Yes, the curl-up is flexion. It's a small, controlled amount of it with your low back kept flat, and it's in a stable position. Your back won’t explode, remember?

I personally perform these exercises (or more difficult variations) 5 days per week. They’ve been foundational to my recovery and spinal health.

As always, have a great weekend.

Best,

Mitch

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References

[1] Callaghan & McGill, 2001 — 10.1016/S0268-0033(00)00063-2. Intervertebral disc herniation: studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force. Clinical Biomechanics, 16(1), 28-37.

[2] Axler & McGill, 1997 — 10.1097/00005768-199706000-00011. Low back loads over a variety of abdominal exercises: searching for the safest abdominal challenge. Medicine and Science in Sports and Exercise, 29(6), 804-811.

Disclaimer: this content is educational only and does not constitute medical advice. See a practitioner if you suspect serious spinal trauma from a fall or accident, or if you experience any of the following red flag symptoms: loss of bowel or bladder control, numbness in the groin or saddle area, rapidly worsening leg weakness, back pain with fever or feeling generally unwell, or unexplained weight loss with back pain.