Want powerful abdominal muscles? Merely aiming for a six-pack isn’t the solution: A six-pack only targets one abdominal muscle, whereas there are actually four essential muscle groups you need to concentrate on for a robust core. The most intense abs workouts don’t just focus on that one muscle, but rather engage all of them.

“For optimal outcomes, both aesthetically and functionally, you must target all the muscles in your abdomen,” elucidates Joan Pagano, an ACSM-certified exercise physiologist and NYC-based trainer.

Here’s a breakdown of your abs muscles: On the side of your abs, you possess your external abdominal obliques and your internal abdominal obliques. Your external obliques reside on top and are those muscles you sense on your side, just beneath your arm. The internal obliques are deeper muscles lying underneath your external obliques, serving as stabilizers to assist you in maintaining your posture.

The transversus abdominis represents your deepest muscles, encircling your midsection horizontally. Strengthening these establishes a “natural girdle” to keep your stomach tucked and stabilize your pelvis, affirms Pagano. Then, of course, there’s the most superficial muscle group in the abdomen: the rectus abdominis, also known as the muscle you see when you envision the classic “six-pack” abs. This group extends from the sternum to the pelvis, facilitating spinal flexion during walking.

A solitary exercise does not target all these muscles. Comprehensive, intense abs workouts incorporate a variety of exercises that engage each region. Ahead, Caroline Gogolak, co-founder of Carbon38 and founder of Saint Art, demonstrates the finest demanding abs moves that target all areas.

At first glance, these exercises might not appear to be the epitome of the most demanding abs workouts. It’s up to you to adapt them to your fitness level. You can always increase the number of repetitions, decrease your rest periods, or repeat the entire routine to create a greater challenge. Progress at your own pace, performing the ideal number of repetitions and sets for your body. (Next up: Conquer this 30-day abs workout challenge.)

B. Exhale, pulling navel towards spine while rolling back onto tailbone, curving spine into a “C” shape. Inhale and realign spine to straighten up. (Want more? Continue with the finest exercises for lower abs.)

2. Twisting Roll-Back

Works: Inner and external obliques, rectus abdominis

A. With arms extended forward, perform a roll-back, curving spine into a “C” shape.

B. Rotate torso to the right, bending right elbow and pulling it back at shoulder level while reaching left arm to right knee.

C. Extend both arms forward and return to starting position.

D. Switch sides; repeat. Continue alternating.

3. Medicine Ball Sit-Up

Works: Transversus abdominis, rectus abdominis, inner and external obliques

A. Hold a medicine ball overhead and recline all the way down to the floor.

B. Lift from core back to a sitting position, keeping the ball overhead.

Scale up: To make this more challenging, find a slant board at the gym or purchase one. Hook feet under the top of the board. The downhill slant and extra weight add an added challenge to the abs. Increase the angle of the board and the weight of the ball for more of a challenge.

4. Kneeling Crunch

Works: Rectus abdominis, inner and external obliques

A. Kneel with right arm stabilized directly under shoulder, reaching left arm forward at shoulder level and right leg back at hip height.

B. Exhale, contract abs, and round back up to the ceiling while drawing left elbow to right knee, turning palm up.

C. Do one set, then switch sides; repeat.

5. Dead Bug

Works: Transversus abdominis, inner and external obliques

A. Lie on back with legs raised, knees bent over hips and calves parallel to the floor. Extend arms to the ceiling with palms forward, and pull abs tight, bringing navel to spine.

B. Exhale, lowering left arm and right leg toward the floor, bringing left knee in over chest. Keep low back connected to the floor at all times — don’t arch.

C. Switch sides; repeat.

6. Lunge Split Jacks

Works: Rectus abdominis

A. Stand with feet in a staggered stance, left foot two to three feet in front of right foot, then lower body into a split squat.

B. Jump up and scissor-kick legs, landing with right leg two to three feet in front of left. As soon as feet land, lower body into a split squat.

C. Continue alternating.

7. Toe Dip

Works: Transversus abdominis

A. Sit tall with both knees bent in front of body, feet flat on the floor. Lean back onto elbows with shoulder blades down and together. Tighten abs, sliding hands under lower back for support with palms facing down.

B. Lift legs so that knees are bent over hips with calves parallel to the floor. Inhale and dip left toes to the mat while maintaining right angles at the knees.

C. Exhale, then return to starting position.

D. Switch sides; repeat. Continue alternating.

8. Bicycle Crunches

Works: Internal and external obliques, transversus abdominis

A. Lie flat on the floor with lower back pressed to the ground; pull abs downward to target deep abs muscles. Interlace fingers and put hands behind head. Start by bringing knees in toward chest, lifting shoulder blades off the ground.

B. Straighten left leg out to about a 45-degree angle from the ground while turning upper body to the right, bringing left elbow toward right knee. Make sure ribcage is moving, not just elbows.

C. Switch sides; repeat. Continue alternating, creating a “pedaling” action. Do this exercise with slow and controlled motion.

9. The “Jean-Zip”

Works: Transversus abdominis

A. As if zipping up a tight pair of jeans, “scoop” abs by pulling navel in toward spine and then up, lifting the pelvic floor. This move engages those deep abdominal muscles.

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