One-Armed Kettlebell Swings For Rotational Core Stability

Using the One-Armed Kettlebell Swing to Build a Steely Strong Core

Although most of the movements we do in the gym are bilateral – from squats and deadlifts to the various types of presses and pulldowns or pullups – most of the movements we do in real life are unilateral.  Hammering in a nail or sawing on a piece of wood?  Unilateral.  Tennis, baseball and boxing?  Unilateral.  Carrying a heavy case up a flight of stairs?  Unilateral.  And most of them require the core to stabilise a movement that we barely do in the gym at all.

The key to generating power is rotation: just watch a shot-putter or javelin thrower, or a boxer throw his hardest punch, his hip exploding into the blow as he rotates his whole body into it.  Rotation has to be both developed and resisted by the core – when  that same boxer hits the bag, its inertia resists the force of his blow and he has to cope with that as well as the energy required to develop the force in the first place.  All this comes from the core.

The core has to be able to both produce and resist forces of extension or dorsiflexion, flexion or anterioflexion, lateroflexion (bending sideways) and rotation.  And rotation is definitely the hardest one to train for in a conventional gym, especially since old-fashioned lifts like the bent press have gone out of style and virtually no-one rotates under a load any more.  So what can we do about that?

Well, there’s always the one-arm kettlebell swing.

When you swing with both arms, the core has to produce and resist forward-and-back forces – dorsiflexion and anterioflexion.  But when you swing with one arm, the load is attached to only one side of your skeleton.  So the other side is unloaded?

Not a bit of it. 

If you hold a weight in your right hand, the muscles of the left side of your body now have to cope with a load that’s off-centre, so there’s more leverage involved.

On the other hand, there’s a phenomenon that allows you to be significantly more than half as strong with one side as you are with both, and it’s called bilateral deficit.  That means that the muscles on both sides firing together can sometimes tell each other to fire a bit less (by way of complicated stuff that goes on in the nervous system, but that’s the general idea).  As a result, many movements can be loaded with 60% or more of the bilateral load for unilateral movements.  Do them on both sides and you’ve used 120% of the unilateral load – 120% of what you could have done by loading both sides equally.  That’s a massive training stimulus. 

The kettlebell swing is one of those exercises like the pullup, the pushup and the squat.  Everyone should know how to do it and everyone should do it.  But we all had to learn, so if you can’t do it yet don’t feel bad. 

How To Do The One-Armed Swing 

Instructions for how to do the unilateral version    

Kettlebells normally come in 2 to 4 kilo gradations: 8, 12, 16, 20, 24 for higher weights and 2, 4, 6, 8 for lower ones.  If you normally use a 16, say, halve that weight and then use the next size up from that once you’ve nailed the movement.  So if you normally use a 16kg bell, use a 10kg with one hand.  If you normally use a 12, use an 8.  If you normally use a 40kg bell I doubt you need advice from me!

Start with the bell on the floor between your feet.

The handle should point front-back not side to side.  Grasp the handle with your little finger facing forward and your thumb facing back.

When you stand out of this position, keep your lower back tight and your arm loose, and the bell will naturally swing forward slightly.

As it reaches the apex of its forward swing, pull the bell back down and hinge at the hips.  At the bottom of the swing movement, explosively drive the hips forward and pull the bell towards you with your upper back muscles at the same time.

When you swing, your arms shouldn’t bend at all.  None of the power in the swing comes from your arms bending, it’s all from your back and hips. 

The swing should move between a position that looks like the bottom of a deadlift, with your body almost, but not quite, parallel to the floor, and a fully extended standing position with your shoulders drawn back and your hips extended.  It’s not a bad idea to practice this motion in a mirror until you can do it without allowing your lower back to bend at all.

It’s tempting when you begin learning to swing to try to ‘pull’ the kettlebell forward from the bottom position.  But that isn’t how it works.  You pull the bell down, and then drive it up with hip extension when you stand.  The bell should end up straight out in front of you.

When you swing with one arm, the bell should end up out in front of you with your palm pointed to the floor, but as it swings back down between your legs your arm should turn to allow your elbow to face forwards and your thumb to face back.  That means your elbow can flex very slightly to protect the elbow joint.

At the bottom of your one-armed swing, the shoulder of your weighted arm should be slightly, but only very slightly, lower than that of your other arm.  At the top, they should be level.  Obviously, that means that you have to rotate slightly to produce the movement, but more importantly you’ll have to resist the rotation the bell tries to impose on you.  It’s that resistance to the rotational force of the bell that allows you to build a steely-strong core as you swing.

We looked earlier at how you can move more than half the load with one hand that you can with two.  So why are one-armed pushups so difficult?  After all, they’re clearly far more than twice as difficult as two-armed ones.  The answer lies in the rotation that your core has to resist to keep your body in the plank position.

It’s the same with one-armed swings.  The benefit isn’t really to your arm but to your core, which has to create the power behind the swing and resist the inertia of the kettlebell as it tries to twist you towards it.  The top position of the one-armed swing mirrors the pattern of force when you throw a ball, for instance, except that the ball would be in the unweighted hand.  

How much you swing with one side is really down to the same kinds of things as how much you swing with both hands.  Most people use a heavier bell for more strength-oriented training and a lighter one for more endurance oriented training, so it’s not unusual to do very heavy swings for sets and lighter ones for time, or in ladders or intervals.  It’s best to avoid hard conditioning like interval training with a unilateral movement because of the increased risk of injury, especially if you’re new to it, but it’s a great way to ramp up your strength and muscular endurance training.  And you’ll feel the benefits on the sports field and in everyday life too!