Last updated: Jun 03, 2016

This ultimate isometric exercise engages the muscles in your abdominals, lower back, hips, and arms. It’s not a surprise that many workouts begin and end with a some variation of a plank challenge. But do you find yourself lowering your hips or arching your back after a few seconds of holding it together? We feel you.

That’s why we tapped Gregg Cook, Daily Burn 365 trainer, to share his expert tips on how to do a proper plank. Plus, you’ll get tips on how to make planks more challenging as you get stronger.

“If you’re new to planks, you can start by doing an incline push-up on a chair. This is actually a more preferable modification than going on your knees because you’re engaging the muscles you’ll need to do a proper straight-arm plank,” Cook explains.

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Or, you can try holding your plank for 10 to 15 seconds and gradually build your way to 60 seconds, Cook recommends. Some people choose to do planks on their forearms before pushing up to their hands. If this is your preferred stance, it’s important to keep your hands shoulder-distance apart, arms forming a right angle to the floor. Your shoulders should also be in line with your hands and not in front of them.

Here are also some other common plank mistakes people make, and how to correct them.

The 3 Most Common Plank Mistakes

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Mistake #1: Arching your back

If your abdominals aren’t engaged, your arms will tire out from supporting the majority of your bodyweight. When that happens, your first inclination is to arch your back, which puts undue pressure on your spine. No bueno, Cook says.

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How to fix it: “There’s a lot of unnecessary shrugging that occurs when holding a plank. Make sure your shoulders are depressed (wide) and that your palms are also wide on the floor,” Cook says. By broadening your shoulders, you will take weight off of your upper body and engage those core muscles that need to be working.

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Mistake #2: Lowering your hips

When your abdominal and arm muscles start to fatigue, it’s likely your hips will begin to sink. (Gravity, ladies and gentlemen!) The downside to letting it all hang down: Your core muscles will be less challenged in this position, and you’ll be putting strain on your lower back. Not the goal here.

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How to fix it: Cook says to keep your hips raised by tucking your butt in a little and squeezing your glutes. You can also walk your feet out apart from each other a bit to give yourself a more stable and solid base. Take deep breaths as you contract and engage your abdominal muscles. No clue if you’re getting it right? You can use a bar (as seen in the photo above) as an alignment check.

RELATED: 7 Easy Ways to Improve Your Squat

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Mistake #3: Looking straight ahead or up

Another common mistake is cranking your head too far back looking up at the ceiling or straight ahead. This can put a strain on your neck, and as a result, the rest of your form will fall apart.

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How to fix it: Keep your eyes looking down at the floor or mat so your head and neck are in alignment with the rest of your body. Cook also suggests thinking about drawing your chin in towards you — especially when you hit that 60-second mark. Gritting teeth, optional.

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This article originally appeared on DailyBurn.com.