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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.