Bet you’ve never actually thought about it.

When someone says “muscle” to you, what’s the first word that comes to your mind? Something like “strength,” right? That’s not wrong; having developed muscles gives you more strength. But people assume that “strong muscles” mean the ones in your biceps. Buff arms help you lift stuff, but there’s another group that lets you keep lifting: the core.

Your core muscles are the ones in the center of your body. Your abs are sort of the poster boy for the core, but really, your core is made up of your entire middle section. The core muscles provide stability to your hips, torso, and shoulders. If you had buff arms but no core beef, your arms would wobble all over the place when they try to lift something.

Your core also acts as protection and a buffer for your spine, one of the most important parts of your skeleton. With the amount of bending a human does on a regular basis, the spine is exposed to some regular wear and tear. With the cushioning power of your core, your spine is protected from permanent damage. That’s especially important when you’re lifting things a lot, as your core muscles allow you to transfer weight from your lower section to your upper section. Without core muscles, if you tried to lift a heavy load, your spine would snap like a toothpick.

It’s important to train your arms, and you should never skip leg day, but above all else, keep that core strong. It’s called the “core” for a reason, after all; it’s core of your muscular structure.