If you’re seeking stronger abs, you’ll be hard pressed to find a core routine that doesn’t include planks. Gone are the days when people crunched to oblivion (while wearing headbands and leg warmers) in order to build core strength. The plank is in, and it’s here to stay.

Planks are one of the best bodyweight exercises you can do to strengthen your abs. And the best part is you can do them in super small spaces—even a shoe-box sized apartment—with no equipment at all. (Sharing an apartment with your best friend? Try these at-home partner workouts.)

Planks help you build strong ab muscles, which can help reduce back pain and prevent back injuries, all while improving your posture. Don’t care about a strong core? Having a sound center improves your functional fitness. That’s the physical strength you need for everyday things, like carrying groceries, picking up children, storing a heavy box on a high shelf in your closet. You’ll be less likely to experience back pain after organizing and cleaning if your middle is strong.

It may look easy to hold your body up, but this isometric strength exercise is challenging. It builds stability of the core muscles, which support proper posture, according to the American Council on Exercise.

Try these planks exercises in your living room, when you’re taking a break from watching TV, in between playing on the floor with pets or children, or, every time you finish a chapter in your book. (While you’re cooking dinner, these kitchen exercises will fire up your whole body.)

At-Home Plank Exercises That Flatten Your Belly

Full plank

Start out in a push-up position with hands under your shoulders and legs stretched out behind you. Keep your body in line, making sure hips don’t go up or sag to the ground. The hands and toes hold up your weight while you brace your core. Hold for 30 seconds at first, making sure your breathing is normal. For a more challenging plank, try the forearm plank where your elbows are under your shoulders, and forearms stay on the floor when you lift up. Give yourself a 30-second rest in between 30-second plank holds. Increase the time you’re holding each plank in 15-second increments as you get stronger.

Side plank with leg raise

Start on your side, forearm on the floor, in the same stacked position as you did with the side plank. Take a breath, contract your abs and lift the hips and knees off the ground. Next, lift the top leg off the bottom one up into the air and hold. Keep that leg parallel to the floor. “Your body should be a straight line from ankle to shoulder and you’ll brace your core while keeping your torso stable in order to raise to raise the top leg,” Sotak says. This will be a tougher challenge to those oblique muscles than the basic side plank. You can either hold this position for 15 to 30 seconds with the leg in the air, or, lift the top leg up and down for 15 reps before switching sides.

Full plank with shoulder tap

Start in the full plank position on your mat or the floor, arms extended. Breathing normally, lift your right hand off the ground and tap your left shoulder. Then place that hand back on the ground. Lift your left hand off the ground and tap your right shoulder. Your body should stay in a straight line, hips facing the ground; the only movement coming from your arms. Aim for eight to 10 taps on each shoulder while starting out, suggests Sotak. Remember to breathe!