Sweat through an ab workout and you want nothing short of rock-hard results. But engaging these muscles does more than just sculpt a bikini-ready bod.

Considered your “vital center” in yoga, your core is critical to overall health. “By focusing on this area, you improve the quality of your digestion and stimulate diaphragmatic breathing, which can relieve the proverbial ‘knot’ in your stomach,” says personal trainer Roman Szpond, owner of Inner Strength studios in Watertown, Massachusetts.

Use the following combination of core strengtheners and stretches to tone your belly — and build a stronger, more centered you.

What It Does: Helps you use your abs in concert (unlike crunches, which isolate one muscle group)

How to Do It: Lie on your back with your arms in the shape of a T and legs lifted so they’re perpendicular to the floor. Shift hips a few inches to the left, then exhale and drop both legs slowly to the right, stopping before they touch the floor. Hold for a deep breath, exhale, and return to the starting position. Repeat on the other side. Alternate for 20 reps, 10 on each side.

What it does: This stabilizing isometric strengthener works the upper and lower ab muscles. To stay balanced here, you’ll use several muscles in concert, which makes more effective use of them.

How to do it: Start by lying on your back, arms over your head and feet hip-width apart. Take a deep inhale and, as you exhale, pull your upper body and lower body upward so that you form a “V.” Reach your fingers toward your toes and keep your gaze upward, compressing your abs and drawing the navel toward the spine. Hold for 3 to 5 seconds, then gently lower down. Repeat 3 to 5 times. (To modify, leave your legs up and just lower your upper body, lifting up again to reach your raised legs.)

What it does: Simultaneously strengthens and lengthens the upper and lower body; stretches shoulders and hips.

How to do it: Lying on your back, cross your left arm under your right, winding your arms around each other so that your palms touch. Wrap your right leg over your left leg (if you can, tuck your right foot behind your left calf) with knees bent. Take a deep breath, reaching arms and legs away from each other, and then crunch, reaching elbows toward the knees. (See next slide.) Lift your upper and lower back slightly off the floor to work the entire abdominal area. Then release your back down to the ground. Exhale and repeat. Do 3 sets of 10.

What it does: Opens up the abs and chest to help calm the body and facilitate breathing.

How to do it: Start flat on your back, then lift up onto your forearms, tucking your hands under your buttocks for stability. Begin to arch the chest, releasing the muscles, widening your collarbone. Rather than drop your head back as in traditional Fish pose, which can strain the neck if done improperly, Szpond suggests keeping your chin tucked. Hold for 3 to 5 breaths, letting your breath rise and fall naturally, your chest open up, and your abs relax. To come out of it, remove your hands and lie down flat, relaxing into the ground.

What it does: Works the oblique muscles (which run along the sides of your core).

How to do it: Pull your knees toward your chest and put your hands behind your head, elbows bent in toward your knees. Extend the right leg and reach your right elbow toward the left knee, as shown here. Then switch, alternating 10 times. On the last rep, freeze, reaching your arm past the outside of the knee for a count of 3. (See next slide.) Do 5 sets.

What it does: Releases the abs.

How to do it: Lie flat on your back with knees bent and arms overhead; take a deep breath and exhale, releasing both legs to your left side. Rest for a few seconds, then reverse. Extend your energy up the arms and out through the fingers. Feel the tension in your ab muscles release. Take a few slow deep breaths. Rest and repeat 1 to 3 times.

What It Does: Stretches the diaphragm and other deep core muscles; massages the colon, stomach, and other digestive organs to improve functioning.

How to Do It: Lie on your back, knees bent, feet on the floor. Inhale and raise arms overhead behind you. Lift your spine one vertebra at a time until your hips are high. Exhale as you relax your abs, lowering your spine down. A natural vacuum will draw your belly in. When your hips are on the floor, lower hands to start position. Repeat 7 to 10 times.

What It Does: Works the diaphragm and the iliopsoas muscles; improves your posture

How to Do It: Lie on the floor with your pelvis resting on a cushion or towels. Reach arms overhead, palms face up. Engaging your core, raise the left leg and lift the right an inch off the floor. Hold and breathe deeply for 30 seconds. Repeat with the other leg, alternating 15 times on each side.