Memorize this move to automatically engage your core when you work out

On arms day, your biceps and triceps are top of mind. But in order to get the most out of those curls and dips, there’s actually another muscle that’s critical in every move you make: your core.

Whether you’re in a spin class, on top of a Megaformer, or just doing some strength training, there’s a reason why trainers constantly tell you to “engage your abs” while you’re working your arms with weights. “Engaging your core is extremely important during all upper body workouts, because it ensures that you are putting less tension in your lower body and using your core stabilizers to assist you,” says Katie Hayes, co-founder of Urban Lagree Megaformer Studio in Austin, Texas. She explains that pulling your navel in toward your spine keeps your body in one straight line and will prevent you from falling forward, particularly when you’re doing moves on an unstable surface (like the aforementioned spin bike and Megaformer). Not only that, but if you’re not working your core enough, it can lead to back pain down the road.

To create your own unstable surface during an upper body workout—and really put your core strength to the test—Obé fitness trainer Peter Tucci suggests challenging yourself with a “flamingo arms” series. This means you’re doing the exercises while standing on one leg, flamingo style. The benefit of this, he explains, is that your core is getting more engagement, since you’re balancing at the same time as doing upper body work. And once you’ve got these moves mastered, engaging your core with two feet on the ground will feel like the most natural thing in the world.

How to engage your core using “flamingo arms”

1. Starting with light weights, stand with your feet together and knees slightly bent, squeezing your inner thighs together. “Imagine a firm yet slightly flexible corset encouraging all the muscles in your midsection to meet at the spine,” says Tucci. Pull your belly button toward your spine, and “imagine the rib cage closing as you broaden the chest,” he says.

2. While keeping your knees and thighs pulled together, bend one leg behind you, kicking your heel up and back. At the same time, do a bicep curl with your elbows slightly in front of your rib cage.

3. Release your heel back towards the ground as you lower your arms. This is one rep. Tucci suggests doing 10 reps on one leg, then switching to the other. Complete three sets for a total of 30 reps per leg (and 60 bicep curls).

Flamingos aren’t the only animal we’re borrowing from when it comes to our fitness routines: “Bear planks” and “alligator crawls” will both make your entire body roar.