Few Exercises Are as Difficult as the Notorious “Copenhagen Plank”

Planks suck and this one is the worst.

The Copenhagen plank is a variation on the toughest part of your mat Pilates class: the already notorious side plank. This version specifically targets the adductor muscles (a group of five muscles in the inner thigh). We tend to neglect these muscles when working out — the fact that they’re always covered with clothing might have something to do with it — but they play a crucial role in hip mobility, injury prevention and core strength.

You’ve likely seen people in the gym or on Instagram working their abductors, which are located on the outside of the thighs and hips, with exercises like lateral leg raises, lateral band walks and clamshell raises. Those are all worth your time. But the adductors deserve your attention too, and the Copenhagen plank, unpleasant as it is to perform, is an effective DIY solution. It easily fit into any workout-from-home regimen; all you need is a workout bench, chair or ottoman.

Here’s a look at one variation of the hold:

You want to place your shin on the bench, then orient yourself in a traditional side plank, with your elbow aligned under your shoulder. The more bench you have under your leg, the “easier” the plank will feel (in relative terms, obviously). So if you adjust the position to have just your ankle touching the bench, there’s less of a lever, and it forces your body to work overtime to maintain stability.

In most planks, the marching orders are simple: keep good posture, avoid rocking back and forth, activate the core and the glutes. The endgame is stronger abs and obliques, in addition to general, full-body fitness gains. You definitely want to squeeze the glutes here, but think less about the core, and more on squeezing your shoulder blades together (which should keep you from falling over) and letting the adductors do their thing. They’ll start firing the second you get into the plank.

The good news? Unlike most plank holds, which encourage 60 seconds or more of isometric agony, the Copenhagen plank is a brief affair. Just 10 seconds at a time, over three sets, is a great place to start. That said, make sure to schedule it for the beginning of your mat workout (the way you want to do dips or pull-ups before getting into the heavy stuff), because it’s extremely difficult.

Once you master the general pose above, try a more advanced pose, like this one, performed by a Men’s Health contributor. Notice how he’s pulled that bottom “free” leg forward to a 90-degree angle, similar to a runner lifting his leg in the air. The adductor muscles do their best work when we’re on one leg (walking, jogging, running). They facilitate that natural contraction. Strengthening and stabilizing them in the Copenhagen plank arena will better equip them for all your day-to-day movement.

At the end of the day, we don’t like planks either. But they’re far too effective to ignore.

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