There isn’t just one ab workout that works and, while many have tried to come up with the perfect ab workout, there are plenty of different exercises that help build muscle. Between the bicycle crunch, pike, and plank, there are numerous exercises that create a muscle building ab workout.

Hanging Knee Raise or Leg Raise: There are different reasons to do leg raises, and there are also some variations to this exercise. Start by doing bent knee lifts and work your way up to straight leg raises. By the time you are doing straight leg ones, you will have plenty of strength in your core. Then you can add more difficulty by using a medicine ball between your ankles or knees. Get your legs as high as you can, but try not to use momentum.

Machine Crunch: Ab exercises with extra resistance are a great way to build muscle. You can also adjust the load. Use this as the first exercise in your ab workout and use lighter weights for a burnout round at the end.

Kneeling Cable Crunch: The key to this exercise is to not do it wrong. It can be easy to sit back when doing this exercise, but this forces the hip flexors to do more work. If you are keeping your back flat, then it will limit the degree you can work the abdominals and you have to round your back. Your hands need to stay in the same position near your head for the whole set. If you let them fall, you will bring your upper body and shoulders into the exercise, which takes the focus off the abs.

Decline Bench Crunch Using a Medicine Ball: These crunches will work better than standard crunches because they increase the motion. You can adjust the difficulty for the exercise by changing the bench angle. When you add a weight plate or medicine ball, you will get even more customizable resistance. Be careful not to pull through the thighs since your feet are hooked. Really focus on the contraction and position this in the middle of your ab routine.

Decline Russian Twist Using a Medicine Ball: This is a harder version of a Russian twist and works the obliques and upper abs. In order to get the most out of the exercise, make sure you aren’t letting your arms wave across your body and be out of line with your torso. Turn at the waist and avoid pulling through your hip flexors.

Pike with Exercise Ball: The exercise ball is more important than you think. The pike movement is one of the most effective total ab workouts. Since it targets a lot of the muscles in the abdomen, you can use it to begin your set or finish it.

Plank: It’s easy to change the degree of difficulty with this exercise. Shoot for time rather than reps.

Squat: This may not seem like an ab exercise, but it works the core. Both back and front squats will force the abs to work more, in order to maintain the upright and neutral position you need. To be able to prevent squats from becoming boring, rotate through them in alternate weeks.