The easiest way to wreck plank form is also the most common modification

The proper form for a perfect forearm plank is pretty easy to remember: Ass down, abs tights, try not to cry while your trainer makes you hold it for three minutes. But if you’re anything like me, you’re constantly looking for ways to make the move easier without sacrificing its benefits. And until recently, I thought I’d found the world’s best cheat: Clasping my hands together on the ground. It made my planks so much less painful, and because no trainer had ever corrected me, I figured I was good to go.

That is, until a trainer at SLT this morning completely burst my bubble, and let me know that actually, I was doing myself a disservice by trying to hack my way through my core workout in this way. “The ideal position for your forearms in a plank is to have them parallel to one another—think like the number 11,” says SLT instructor Amanda Jenny. “Your elbows should be directly under your shoulders and your palms should press down into the carriage. When you clasp your hands, it often causes the upper back to round, the shoulders to cave in and the elbows to slide out from under the shoulders. As a result, your form and posture will suffer.”

So basically, even if the rest of your form is perfect, holding your hands together can mess it all up, which is not exactly the best news to someone who’s been working this modification for going on 15 years. To master the perfect forearm plank, instead, place your elbows directly underneath your shoulders with your shoulders externally rotated. Tuck your pelvis underneath you to fire up your abs, contract your glutes, and push into the floor with your forearms. Sounds easier than it is, I know, but at least it’s fairly straightforward.

One other interesting tidbit of plank knowledge worth pointing out: While you may think forearm planks are the “easier” option instead of doing them on your hands, the two moves actually work different muscles. “Performing planks on the hands is more challenging for the shoulders and triceps while performing the exercise on the forearms is more demanding for the core,” trainer Eric Johnson recently revealed. The more you know!

To take your plank workout to the next level, try the sequence that was so hard it legit made me cry, or the 2-minute series that will leave your abs on fire in less than 120 seconds.