If asked to give an example ab exercise, the majority of people would undoubtedly say “crunches.” Crunches, and their sister move sit-ups, are an OG core move that the fitness world has been doing for ages. But, according to a chiropractor, these happen to be the worst things that you can do for a stronger core.

The issue? Crunches and sit-ups both involve folding your body inward. “People are sitting all day, looking down at their smartphone or their computer, but what people really need to do is more extension,” says Todd Sinett, DC, a chiropractor and kinesiologist (whose book, Sit-Ups are Stupid and Crunches are Crap, comes out this spring). “Our core is actually over-contracted and too tightened—so it’s too tight, not too weak.” Moves that literally crunch (ahem) your body even more throw off your alignment and your posture, which can lead to back pain.

Simply extending your spine and opening up your core, on the other hand, strengthens the important muscle groups around the abs that are key for holding yourself upright. Dr. Sinett points out that extension-based core exercises work “all of the supporting core musculature in a symmetrical and systemic fashion,” while also keeping your back straight (studies even prove it). Things like standing ab exercises, twists, and basically anything that burns your core without contracting your spine all fit the bill Keep scrolling for Dr. Sinett’s recommended exercises to strengthen a weak core.

Back-friendly core exercises

1. Dead bug: Lie down on your back, legs in tabletop position, arms extended above your chest. Extend your right arm overhead and your left leg long, then switch sides.

2. Standing abdominal twist: Standing upright with your legs out wide, bend at your torso with your arms extended to your sides, in line with your shoulders. Rotate your torso and move one arm straight up to the ceiling with the other one touching the floor. Switch sides.

3. Boat pose: Seated on your mat with your knees bent, feet on the floor, grab the back of your knees or extend your arms in front of you. Hold while engaging your core. For more of a challenge, extend your legs on a diagonal.

4. Leg raises: Lying on your back, raise both legs up straight. Slowly lower them down without touching the floor. Repeat.

5. Plank: Yes, Dr. Sinett believes that the plank is a good core-working move. Place your hands on your mat beneath your shoulders, feet straight behind you, back straight. Hold it for about one minute.

Check how to do a proper plank, below. 

For more ideas, add these standing ab exercises to your core-busting workout. And don’t forget the super-hard bear plank, which makes your entire body roar.