Crunches, mountain-climbers, and planks probably already make frequent appearances in your workout routine—because who doesn’t want a strong core and a six-pack? But if there’s one part of your core that could probably use a little more attention, it’s your obliques. You know, your side abs!

Your obliques muscles (you have internal and external obliques) run along the sides of your torso, and are important for stability and balance, posture, and supporting your lower back, explains Grayson Wickham, D.P.T., C.S.C.S., founder of Movement Vault.

While exercises that target your abs usually involve lots of crunch-type movements, exercises that hit your obliques involve a lot of twisting and side-bending, says Wickham. (But they’ll fire up your abs, too.)

Below are nine exercises trainers turn to when they want to really fire up their obliques and develop overall core strength. Try adding three sets of 10 to 15 reps of a couple of these moves to your next workout, suggests Wickham. (Just remember that visible obliques require a healthy diet and low body fat percentage.)

Move #1: Side Plank

Equipment needed: None

What you do:

1. Lie on one side with your legs and feet extended straight out and stacked with one on top of the other.
2. Prop yourself up on your forearm and raise your hips so that your body forms a straight line from your head to your heels, facing the side of the room. Engage your core and glutes to keep your hips up.

Why it works: This plank variation requires full-body stabilization and activates glutes, quads, hamstrings, delts, shoulders, and all of the core muscles, explains Yusuf Jeffers, C.P.T., head coach at Tone House. To make this move harder, first try raising yourself from your forearm to your hand, so that your arm is straight, with your hand below your shoulder. To turn up the heat even more, lift your top leg up toward the ceiling. Try to hold your side plank for at least 10 seconds, adding time as you get stronger.

Related: The 5 Most Effective Abs Moves

Move #2: Hip-Up

Equipment needed: None

 What you do:

1. Lie on one side with your legs and feet extended straight out and stacked with one on top of the other.
2. Prop yourself up on your forearm and raise your hips so that your body forms a straight line from your head to your heels, facing the side of the room. (Side plank.)
3. Raise your top arm up so that it is perpendicular to the floor.
4. Lower your hips down to the floor, then raise them back up into the side plank position.

Why it works: Consider the hip-up a higher-difficulty variation of the side plank, says Jeffers. You’ll get that same full-body engagement, with an extra challenge. “The movement of dropping your hips and raising them back up is almost completely in your obliques,” he says. To make this one a little easier, drop to your knees, so that they’re stacked one on top of the other, instead of your feet.

Move #3: Lying Windshield Wipers

Equipment needed: None

 What you do:

1. Lie down on the floor with your belly up.
2. Spread your arms straight out to your sides, so your body forms a ‘T.’
3. Raise your legs straight up toward the ceiling, so they form a 90-degree angle with your torso.
4. Keeping your shoulder blades on the floor and legs glued together, rotate your legs down to the left. Stop when your right shoulder starts to peel up off the floor.
5. Rotate your legs back to starting position.
6. Repeat the leg rotation on the right side.
7. Rotate your legs back to starting position.

Why it works: The side-to-side rotating movement of your legs engages your obliques big time. The more you do this exercise (and the stronger your core gets), the closer you’ll be able to lower your legs to the floor, says Jeffers. And that’s a good sign for both your obliques and you’re your flexibility.  As you get better at this one, rest your arms closer toward your body so that they provide less stability.

Move #4: Weighted Lying Windshield Wipers

 Equipment needed: Empty barbell or PVC pipe

 What you do:

1. Lie down on the floor with your belly up.
2. Hold your barbell or pipe straight above you so that your arms are locked out and form a 90-degree angle with the rest of your body.
3. Raise your legs straight up so they also make a 90-degree angle with your torso.
4. Keeping your arms straight, shoulder blades on the floor, and legs glued together, rotate your legs to the left side. Stop rotating when your right shoulder blade begins to peel up off of the floor, or your feet are two to three inches above the ground.
5. Raise your legs back to starting position.
6. Repeat the leg rotation on the right side.
7. Raise your legs back to starting position.

Why it works: The weighted lying windshield wiper movement activates your obliques muscles with each side-to-side movement of your legs, but is a little more challenging than the standard windshield wiper. That’s because holding that weight as you rotate requires a tremendous amount of upper body strength, explains Wickham.

As you improve, increase the weight of the barbell. For example, if you started with a 15-pound training bar, bump up to a 35-pound barbell. If you used a 45-pound barbell, add a five-pound plate to each side.

Move #5: Hanging Windshield Wipers

 Equipment needed: Pull-up bar

 What you do:

1. Hang from a pullup bar.
2. Raise your legs until they are perpendicular to the floor. (You should be in an ‘L’ shape.) To keep your torso straight you will have to engage your upper back muscles by pulling your torso underneath the bar and contracting your back muscles.
3. Engage your upper back to keep your torso underneath the bar, then rotate your legs from side to side.

Why it works: Once you’ve mastered Lying Windshield Wipers, you can move on to this one. It requires a tremendous amount of core strength and control, explains ICE NYC HIIT coach Margie Welch. The key is actively engaging your shoulders and back instead of just hanging loosely from your arm sockets. (If you can do the lying version no problem, but have trouble with the hanging version, you may need to work on your upper-back and grip strength, she says.) To make this move easier, bend your knees at a 90-degree angle.

Related: 8 Pullups To Challenge Your Upper Body

Move #6: Side-to-Side Medicine Ball Wall Throws

Equipment needed: Medicine ball and wall

What you do:

1. Stand next to a wall (about three to five feet away) with your feet shoulder-width distance apart.
2. Hold a medicine ball between your hands at chest level.
3. Straighten out your arms so they’re parallel to the floor.
4. Rotate your torso towards the wall and release the ball. It should hit the wall and bounce back at you. (If it doesn’t quite make it to you, take a step closer and try again.)
5. Catch the ball and return to your start position.
6. Repeat. Switch sides after the prescribed number of reps.

Why it works: This move requires core stabilization, upper-body strength, and endurance. “You’ll be surprised how quickly this one tires you out” says Wickham. The key to this core move is explosiveness, so make sure you’re rocketing that ball into the wall. (It may take some trial and error to figure out how far from the wall to stand. You’ll need to stand further away with a heavy ball than you would with a lighter one.) Increase the weight of the ball and the number of reps you perform as you get stronger.

Move #7: Diagonal Ball Slam

Equipment needed: Medicine ball

What you do:

1. Stand with your feet shoulder-width distance apart and a medicine ball place on the outside of your left foot.
2. Keeping a neutral back, bend down and pick up the ball. Raise it up over your head, as if drawing an arc in the air.
3. From this overhead position, slam the ball back down toward the outside of your left foot. (The ball should be moving in a diagonal line.)
4. Repeat on other side.

Why it works: The diagonal movement here really fires up your obliques; just make sure you use a ball you can slam with force, says Wickham. As you progress, increase the weight of the medicine ball or the number of reps you perform.

Move #8: Kettlebell Windmill

Equipment needed: Kettlebell or dumbbell

What you do:

1. Stand with feet just wider than hips-width distance apart with a kettlebell on the ground in front of you.
2. Lift the kettlebell above your head and hold it overhead with one hand.  Extend your free hand toward the ground.
3. Keeping the kettlebell locked out at all times, push your hips and butt back toward the side the kettlebell is on.
4. Bending at the hip to one side, sticking your butt out, slowly lean as you slide your free arm down your leg until you can touch mid-calf or the floor. (Keep your eyes on the kettlebell at all times.)
5. Pause for a second after reaching the ground, then reverse the motion back to the starting position by shifting your pelvis back to center to redistribute your weight evenly between both feet. Keep the kettlebell extended and slide your fingertips up your leg.

Why it works: This oblique move is no easy task. It requires full-body stabilization, shoulder and arm strength, and maximum oblique flexibility and strength, explains Wickham. You’ll even feel it in your glutes and hamstrings. For that reason, Wickham recommends beginners try the move without any weight. Once you get the hang of the movement, you can add a light kettlebell to the equation. From there, you can increase the weight of the kettlebell as you get stronger. “When you use a weight, keep your eyes on the kettlebell overhead the entire time, this will help you maintain correct form and alignment of the shoulder” says Wickham.

Related: Find a supp to help your muscles reap the benefits of a good workout.

Oblique Movement #9: Weighted Twist (Russian Twist)

Equipment needed: Kettlebell, dumbbell, medicine ball, or weight plate

What you do:

1. Sit down with your legs together straight out in front of you. Bend your knees to form a 90-degree angle and plant your heels on the floor.
2. Hold a five to eight-pound weight between your hands.
3. Keep a flat back and twist your torso to the left. The weight should twist with you.
4. Stop twisting when you feel a stretch in your obliques.
5. Reverse your twist back to the middle and then twist to the right.

Why it works: This exercise, which really fires up your obliques thanks to that twisting movement, really hits your whole core. “This movement focuses on both the external and internal obliques and the rectus abdominis, or the washboard muscle,” says Welch. Beginners can practice the move without added weight and touch the ground on each side as they rotate. For an extra burn, try lifting your heels and hovering your feet above the ground as you rotate.