Are these exercises damaging your back?

Are these "ab exercises" damaging your spine?

If I ran a ‘’spine lab,’’ where my job was to take lumbar disc and create a bulge or herniation in them, I would repeatedly flex them, compress them, and if possible combine that with rotation. And that’s exactly how most patients finally develop a disc issue. Usually its repetitive, but then there’s typically that ‘straw that broke the camel’s back’ moment where there is bending (flexion) with rotation, under load.  Luckily for us, Professor Stu McGill PhD has a lab just like that and has done a great deal of research on it.

Spine flexion produces a posterior shear force on the nuclear material in the disc; pushing it backwards towards the spinal nerves.  It must first derange the outer, more fibrous, annular fibers.  Theses annular fibers are arranged like plywood, with crisscrossing fibers, adding strength to them.  Rotation, or twisting, of the disc aligns these fibers reducing their strength by a huge margin.  Life is hard enough on our spines, training should not be chipping away at our tissue tolerance, but instead training it to be more durable.  Allow me to help you.

There are too many “Ab” exercises that mimic these motions.  My goal is to highlight the absurdity of them, and provide safer more effective training options. I have picked three common ones that gym folk might be using. One for the front, the side and the back; or for the rectus abdominus, the obliques, and the posterior erector spinae.

Scroll down to see my video detailing these

A Newton (N) is a measurement of Force (Mass x Acceleration). Named for Sir Isaac Newton, and his work in mechanical physics, it is used in quantifying spine loads. It’s not exactly a like pound or kilogram, which are measurements of Mass, but here on Earth (and gravity providing the acceleration) you can think of 1N as the weight of an apple, henceforth a Newton, or one pound is about 4.5N.  The reason I tell you this in regards to back pain and spine loads in training is so you can somewhat visualize the compressive forces imparted on your spine with various exercises.

The Russian Twist

Let’s start with this VERY common one, that also happens to be the worst on the spine too.  Seated, with a weight on your chest, hold a partial situp position (around 45deg) and rotate your chest and the weight side to side.  Bonus points if your feet are off the ground.  Double bonus points if your legs are also extended, making a V shape with your body. The thought is that it trains the obliques very well. I thoroughly disagree. No doubt it is hard, no doubt that it loads the muscles, but at what cost? And to what benefit?

This is a flexed posture, so disc pressure is biassed towards the nerve roots.  Professor Stu McGill, world renown spinal biomechanist, measure’s a sit-up (with a 150lb man) as producing 3000N, or about 675lbs, at the L4/L5/S1 segments, the lowest part of your low back.  But that number is just the beginning.  For one you probably weight north of 150, and adding a weight, at a reasonable distance from the low back, produces a torque on the spine.  That 10kg on your chest or in your hand is multiplied by the distance from your spine.  It’s reasonable to assume that the force is easily over 1000lbs….and you’re then going to twist.

Maybe you’re durable and you don’t break; but your spine will undoubtedly be more susceptible to injury in the future.  Not to mention that this sort of oblique training may be decently good enough at body builder type training, but it is not how your obliques are wired to function. In no sport do your obliques get used to CREATE rotation.  See my previous post on DNS where the obliques are used to store energy and resist rotation in a throwing motion.

The alternative:  Stir the Pot

If you’re a gym folk, thirsty for that ab burn that a Russian twist can provide, I can think of NOTHING better to replace it than the “Stir the Pot.”  You see, our obliques do run from rib cage to the opposite pelvis as the external (at the rib cage) and internal obliques (deeper and connecting to the pelvis). And at the rib cage, the external obliques share a huge facial connection with the Serratus Anterior, a shoulder blade muscle that functions to ‘adhere’ the scapula to the rib cage.  The two muscles more or less always work together. The internal obliques connect to the iliotibial tract (our IT band) in the opposite hip/pelvis.  This is all part of a larger fascial connection known as “The Spiral Line.”  Incorporating these connections into training will increase the muscle load. Plus the position is far more spine friendly and it is readily regressed to easier variations, or progressed for the most well trained athletes.

With a gym ball, go into a plank position on it, forearms and clasped hands making a powerful triangle. The more spread your feet are, the easier this will be.  The taller the ball is, the easier this will be.  Maintain a stiff neutral spine and head position, with your hands make circles like your stirring a massive pot of peanut butter.  Change directions at your leisure.  The bigger the stir motion is, the more challenging this will be. For me I like to do 5 counter clockwise, then 5 clockwise, then 4 each direction, then 3, then 2, then 1 each way.  It takes around one minute for me.


I cringe at this one the most, because unlike the others, this one is COMMONLY prescribed as a part of a spine rehabilitation program.  Lying face down, arms up overhead, legs extended outwards, raise your legs, arms and chest off the ground.  The spine load here is not a typo, its over 6000N.  The equivalent to 1350 lbs of pressure on the lumbar spine. Insane that this is used to help patients with back pain.

Alternative: The Bird Dog

From quadruped, keeping a neutral braced spine, extend opposite arm and legs in this contralateral pattern.  This prodices a spine force that is less than 1/3 of that in the superman, and trains the spine as being stiff, not bending under the load. The bird dog should be held for 5-8 seconds, or as I say 2-3 full breath cycles.  It can be advanced by doing consecutive reps (sweep the floor and return), and also by performing controlled specific arm and leg movements from the full position (drawing squares). See the video at the bottom. Performing any good core stabilization exercise under respiratory distress (breathing hard) will also greatly increase the challenge as you “breath behind the shield” of the abdominal wall.

If you feel that you’re missing the burn of the superman, you’re missing the point, it’s about being able to MAINTAIN NEUTRAL, not using the muscles to CREATE movement.  I’d add that if you’re thirsty for that burn,  you need to look elsewhere; do deadlifts and kettlebell swings to really train the muscles of the posterior chain hard.

Hanging Leg Raise

From a pull bar hanging legs straight, raise the legs to 90degs. Professor McGill measures these at 3000N, around 650lbs on your spine.  But the more common crossfit toes to bar is a similar move.  Like most this crossfit, it’s a bit bigger, faster and higher volume.  In a toes to bar the range is bigger (full lumbar flexion) and momentum is used.  Any time momentum is used its difficult to really quantify spine loads as it will vary based on any individuals motor patterns. I was able to find the infamous Mike Boyles words on the matter and I found them humorous and informative:

“I recently heard an anecdotal report about a severe skull fracture from losing grip on Toes-to-the-bar. Most people use momentum to get the last few and if grip fails the results could be catastrophic.Toes to the bar is hip flexion aided by momentum with the hands acting as a fixed point. As many readers know, the psoas pulls directly on the lumbar spine. This sounds like a prescription for failure.People have always liked the hanging knee up exercises ( toes to the bar is simply a more “advanced” knee up) because they make you sore and sore equates with good. The reality is that the abs get sore from attempting to control the eccentric action of the leg lowering. Not a great concept.In any case, I’m obviously not a fan. However, it’s a great exercise for the chiros and PT’s out there as it will keep the patients coming.”

The Alternative: The Dead Bug

This exercise also incorporates hip flexion, but emphasis is placed on neutral spine position.  It too is fairly easily advanced.  In the supine 90/90 position (DNS 3 month supine) lower alternating heels to the floor.  Allow motion to occur at the hip, not the spine.  Add movement of opposite arm for added challenge.  Focus on respiration and a neutral spine. Advance with a touch of rotation of the WHOLE body, tipping towards one side and the next. Advance by increasing how much you straighten the leg reaching down.  Advance by adding pulses of movement in the extremities.

Ab exercises: Bad vs Good


  1. McGill, S. (2002) Low Back Disorders: Evidence-Based Prevention and Rehabilitation. Waterloo: Human Kinetics.
  2. McGill, S. (2006) Ultimate Back Fitness and Performance. Waterloo: Backfitpro Inc.
  3. Callaghan, J.P., and McGill, S.M. (2001) Intervertebral disc herniation: Studies on the porcine model exposed to highly repetitive flexion/extension motion with compressive force. Clinical Biomechanics, 16 (1): 28-37.
  4. Axler, C.T., McGill, S.M., Low back loads over a variety of abdominal exercises: searching for the safest abdominal challenge. Med Sci Sports Exerc. 1997; 29:804-811.
  5. McGill, S.M., The mechanics of torso flexion: situps and standing dynamic flexion maneuvers. Clin Biomech, 1995; 10:184-192.
  6. McGill,Muscle activity and spine load during anterior chain whole body linkage exercises: the body saw, hanging leg raise and walkout from a push-up.Journal of Sport Science 2015;33(4):419-26. doi: 10.1080/02640414.2014.946437. Epub 2014 Aug 11.


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