You’ve read a lot about how important it is to have a strong core.
But you’ve come across plenty of different opinions about the best way to get one.
Some say that squats and deadlifts build all the core strength you’ll ever need.
Others will tell you that the best way to strengthen your core is to spend time on a Swiss ball, BOSU ball or other “unstable” surface.
What Is the Core?
The term “core” causes a lot of confusion, mainly because everyone seems to have a different opinion about what it is.
For most people, the core is just another name for the abdominals. But the term actually refers to a much larger collection of muscles that stabilize the spine. These muscles work together to keep the spine as close to neutral – its naturally curved state – as possible.
Neutral spine isn’t a single position that your spine never moves from. Think of it as a neutral zone, or a range that your spine can move within while remaining relatively healthy. A lack of spinal stability can lead to movement outside of this zone, which in turn increases the risk of pain and/or tissue damage.
“When we talk about stability, what we really mean is that we want the lower back – the lumbar spine – to move as little as possible when it faces a challenge,” explains Lou Schuler in The New Rules of Lifting for Abs. “This small range of movement is called the neutral zone. The smaller and tighter it is, the more stability you have.”
Why Is the Core Important?
When muscles contract, they create stiffness. Not only does muscular stiffness stabilize the spine and reduce the risk of tissue damage, it’s also a requirement as far as optimal athletic performance is concerned.
In the video below, Professor Stuart McGill, an expert in spine function at the University of Waterloo in Canada, explains why a “stiff” core is so important in sports that rely on strength, speed and power.
When the core is mentioned in this context (i.e. as a way of transmitting power) it usually refers to the muscles of the trunk and hips — basically, anything that isn’t the head, arms or legs.
Core Strength: Unstable versus Stable Surfaces
Does exercise on an unstable surface lead to greater activation of the core muscles?
Performing an exercise on an unstable surface, such as sitting on a Swiss ball or standing on a BOSU ball, is supposed to place greater emphasis on some of the muscles in your core, helping to improve core stability, protect against back pain, improve athletic performance, and so on.
Such exercises often appear a lot harder than their more stable counterparts. That’s mainly because you’re working so hard to stay balanced. And because of their high novelty factor, they often create the impression that they’re superior to same exercise done on the floor.
There is research out there to show that an exercise performed on an unstable surface leads to higher levels of core muscle activity than that same exercise performed on the ground .
Squatting with a light weight on a couple of inflatable discs, for example, leads to greater activation of muscles in the torso than squatting with that same weight on the floor .
The big limitation with many of these studies is that they involve the use of relatively light weights. Which is a problem, because most people can lift a much heavier weight when they’re standing on the floor than they can while wobbling about on an unstable surface.
What happens when you compare differences in muscle activity using loads that take into account the fact that you can lift more weight on a stable rather than an unstable surface?
That’s exactly what researchers from Eastern Illinois University wanted to find out . They looked at muscle activation in a group of 12 trained men who performed four different exercises – the deadlift, squat, overhead press, and barbell curl – at two intensities (50% of 1-RM and 75% of 1-RM) while standing on both a stable and unstable surface (BOSU ball).
Muscle activity in the abdominals and lower back was not significantly different when subjects performed the deadlift, squat, overhead press, and barbell curl using a light weight while standing on a BOSU ball rather than on the floor.
What’s more, there was no significant difference in muscle activity between the stable 75% of 1-RM and unstable 50% of 1-RM conditions for the external obliques and lower back across all four lifts.
But when the overhead press was done on a stable surface using a heavier weight, rectus abdominis (the six-pack muscle) was worked a lot harder than it was during the same exercise on a BOSU ball using a lighter weight.
Performed on a stable surface, the overhead press and barbell curl also delivered a decent level of stimulation (40-50% of their maximal voluntary contraction, or MVC for short) to the deeper abdominal muscles.
There is a time and a place for instability. As an example, some of the exercises in the video below (the Bird Dog and Stir The Pot) use instability to place greater emphasis on the core musculature.
And physical therapists have been using unstable exercise devices (e.g. Wobble boards and Rocker boards) for years to help with the rehabilitation of knee and ankle injuries .
But with few exceptions, training with a light weight on an unstable surface isn’t going to work the core muscles any harder than the exact same exercise done with a heavier weight on a stable surface.
Are Squats and Deadlifts All You Need to Train Your Core?
Squats and deadlifts render all direct abdominal work completely redundant, as both exercises provide all the stimulation your abs will ever need.
That’s the theory, anyway. But the research paints a picture that’s a lot less clear cut.
Squats and deadlifts do work many of the core muscles. But it’s mainly the ones in your back, especially the spinal erectors – those cable-like muscles that run up either side of your spine.
During the deadlift in particular, they work very hard to keep your spine in its naturally arched position. Powerlifters have such well-developed spinal erectors mainly because of all the work those muscles do to prevent the spine from bending.
In other words, squats and deadlifts work just fine for developing the posterior aspects of the core. Quadratus lumborum, a small but important muscle in the lower back that helps to stabilize the spine, is also heavily involved during the deadlift .
But what about the abs?
Rectus abdominis, the muscle responsible for the “washboard abs” look, does help to keep your trunk stable during various exercises. And the contribution it makes to trunk stability will increase with progressively heavier weights.
That is, if you’re squatting with a weight that limits you to 2 reps, your abs will be working harder than if you were lifting a weight that lets you get 8-12 reps .
In short, rectus abdominis will be called into action during squats and deadlifts. But simply recruiting a muscle isn’t enough to make it grow. It needs to be both recruited and stimulated to a degree that’s sufficient to send the “make me bigger” signal to that muscle.
And most research shows that rectus abdominis activity during the squat and deadlift is relatively small.
The figure below comes from Dr. Jeffrey McBride, a Professor in Biomechanics at Appalachian State University. He measured muscle activation in the abdominal muscles of trained lifters performing a number of different exercises.
As you can see, squats and deadlifts – even when you’re using a heavy weight that’s 80-90% of your maximum – don’t hit rectus abdominis particularly hard.
Similar results are reported in a trial involving a group of elite male rugby union players .
These were reasonably strong guys, sitting roughly halfway between “intermediate” and “advanced” in terms of squat strength. Not the typical “untrained beginner” often used in this type of study.
The researchers measured muscle activity in the abdominals during the squat, overhead squat, as well as during various abdominal exercises.
Once again, rectus abdominis didn’t have to work very hard during the squat – only around 10% of its maximum. In fact, the researchers found “substantially larger” abdominal muscle activity during the plank, sit-up and jackknife.
In fact, the overhead press has been shown to trigger greater rectus abdominis activity than both the deadlift and squat . But it’s still relatively low compared to exercises like the rollout or even the curl-up.
With all of that said, the research that’s been done on the subject does come with some important limitations.
For one, most studies use electrodes placed on the surface of the skin to measure trunk muscle activity.
But during the lowering phase of the squat, you will lean forward. As a result, skin in the stomach area can fold, moving the electrodes further away from the abs, which may lead to measurement error .
The extent to which rectus abdominis is involved during the squat also depends on who’s doing the squatting.
If you’re squatting with heavy weights, wearing a lifting belt (which has been shown to increase rectus abdominis activity ) and pushing your stomach out when you squat, rectus abdominis is going to be working harder compared to squatting with a lighter weight, not wearing a belt and using a different bracing pattern to create intra abdominal pressure.
Genetics also have a role to play. I’ve known guys who do very little direct abdominal work, yet their abs still pop out.
Someone who can perform a standing overhead press with three-quarters of their bodyweight and deadlift twice their bodyweight will have developed a very high level of core strength simply by focusing on getting stronger in both exercises.
But all things considered, if getting washboard abs is high on your list of priorities, I’d suggest doing exercises that work your abs directly.
While I’m on the subject of core training, I want to briefly mention the issue of spinal rotation.
Probably the most popular “spinal rotation” exercise is the broom handle twist, which is without doubt one of the most pointless exercises ever invented.
That’s not to say there’s no need to train the muscles that twist the torso. But there are far better ways to do it than twisting from side to side with a broom handle on your back.
Rather than rotation, think resisted rotation. And by resisted rotation, I’m talking about exercises that require you to resist forces trying to pull your torso around to the left or the right.
Let’s take the Single Arm Dumbbell Row as an example. Although this is primarily an exercise to work the muscles in your back, the external obliques (the muscles on the side of your waist) are also involved. That’s because they’re actively preventing your torso from twisting.
The same principle applies with other single arm exercises, such as the overhead dumbbell press.
I recently injured my shoulder, which meant I couldn’t do any heavy lifting with my left arm.
However, because of a phenomenon known as “cross education” (where training one limb has a small but significant effect on strength in the other), I wanted to carry on training my right side.
So I did some heavy single-arm pressing using just my right arm. The next day, I could really feel it in the muscles on the left side of my torso. That’s because they were working extremely hard just to keep me upright.
This is a much more efficient use of your training time than doing a bunch of side bends, which also fall into the “not a great use of your time in the gym” category.
The Long Lever Plank Shoulder Tap, demonstrated in the video below by Ben Bruno, is another good example of what I mean.
In the starting position, you’re resisting spinal extension (arching your back), which makes this a particularly effective exercise for working rectus abdominis. Removing one of the contact points (your hand) from the floor introduces an element of instability, which then requires your body to resist rotation.
If you find this exercise too difficult, keep your hands under your shoulders in a push-up position rather than out in front of your body.
Exercises that involve resisted rotation are a far better choice than those involving actual rotation, such as the Russian Twist or Windshield Wiper, both of which make me cringe every time I see someone doing them.
If you have a history of back injury, or even if you have a healthy, pain-free back and want it to stay that way, I’d highly recommend that you steer clear of any exercise that involves this type of movement.
Remember, many of the muscles in the torso can be trained very effectively by preventing movement rather than producing it. You’re still training the muscles involved in spinal rotation, but you’re doing so in a way that poses less risk to the spine. An exercise doesn’t have to involve an actual twist to work the twisting muscles.
That doesn’t mean you should avoid rotation altogether. But make sure the movement comes from the hip, and allow the hip and back to move together at the same time, almost as if they were fused together. Watch the video below to see exactly what I mean.
Building a core of steel doesn’t need to be complicated, time consuming or boring. Nor does it require exercising on a Swiss ball, BOSU ball or any other surface that isn’t the floor.
In fact, many of the muscles in your core work very hard to prevent spinal movement during exercises like squats, deadlifts, single-arm rows, rollouts/walkouts, and standing presses. These movements build not just core strength but whole-body strength as well.
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ABOUT THE AUTHORChristian Finn is the nation’s leading authority on science-based, joint-friendly ways to build muscle. A former "trainer to the trainers," he holds a masters degree in exercise science, and has been featured in or contributed to major media on two continents, including the BBC and Sunday Times in the U.K. and Men’s Health and Men’s Fitness in the U.S.