This 4-Move Ab Circuit Is Perfect for the Gym

While you don't need a single piece of equipment to target your abs, if you have a gym membership, why not take advantage of all the gear you have access to? There's the ab roller, stability ball, medicine ball and captain's chair — all of which will help you sculpt your midsection.

Each exercise works slightly different parts of your abdominals. The most well-known abdominal muscle is the rectus abdominis, which is the muscle that forms the six-pack. This muscle is divided into the lower half and upper half.

The muscles on the side of your six-pack are called the obliques. Technically, the external oblique is the muscle you can actually see and measure and the internal oblique is the muscle hidden underneath.

Read more: The Science Behind the Most Effective Ab Workouts

Each ab exercise works the ab muscles in a different way, so in order to create the best ab workout, you must include multiple exercises. With so many different options how do you know which exercises to do?

In order to find out which ab exercises are the best, researchers measure how hard your ab muscles work in each one. Using EMG, or electromyography, they measure the amount of electrical activity in your muscles and are able see which exercises cause the greatest stimulation.

While each study — like a May 2001 one from the American Council on Exercise (ACE) or a February 2006 one from the Journal of Orthopedic and Sports Physical Therapy — has slightly different results, there are a few exercises that always seem to be consistently ahead of the rest. These exercises are: the ab rollout, stability ball crunch, bicycle crunch and captain's chair.

So why not put them altogether for one supercharged ab workout?

Read more: The 41 Hardest Ab Exercises

For this ab workout, you'll pair these exercises together for supersets, doing one set of an exercise, then immediately going into the exercise it's paired with.

Do: the ab rollout and stability ball crunch, rest for one minute, then do the bicycle crunch and captain's chair (hanging leg raise). Perform each pair of exercises three times.

Move 1: Ab Rollout

Even though this exercise is performed with a fairly simple piece of equipment, it's one of the most challenging and effective ab exercises in the gym, according to the Journal of Orthopedic and Sports Physical Therapy study.

1. Kneel on something soft like a blanket or rolled-up yoga mat. Grab an ab wheel with both hands and hold it on the ground in front of you.
2. Roll the ab wheel forward and push your hips down toward the ground until you form a straight line from your head to your knees.
3. The ab wheel should be directly under your shoulders. This position looks like the starting position of a push-up from the knees.
4. Flex your abs and roll the wheel forward. Keep rolling forward until your arms are alongside your ears.
5. To get back up, pull the ab wheel down toward your knees until you push yourself back up to the start position with the ab roller directly under your shoulders.

Reps: 8 to 10

Read more: Ab Roller Benefits

Move 2: Stability Ball Crunch

A lot of researchers don't like crunches and sit-ups, since they have the potential to put undue strain on the lower back. However, doing crunches on the stability ball can help prevent this. It was also number 3 on ACE's list of best ab exercises.

1. Lie with the middle of your back on a stability ball with your feet close under your knees and knees bent.
2. Cross your arms over your chest or place them behind your head.
3. Breathe out and lift your head, neck and shoulders, curling up toward the ceiling but keeping your middle and lower back on the ball.
4. Lower yourself back down to the mat slowly and with control.

Reps: 15 to 20

Move 3: Bicycle Crunch

According to the ACE research, the bicycle exercise was the best for the rectus abdominis and second best for obliques when compared to 12 other abdominal exercises.

1. Lie on your back with your hands behind your head and legs in the air, knees bent at 90 degrees.
2. Touch your left elbow to your right knee by turning your torso to the right, pulling your right knee back, and extending your left leg out straight.
3. After you touch your left elbow and right knee together, reach your right leg out straight, turn your upper body to the left, pull your left knee back toward your right elbow, and touch them together.

Reps: 10 on each side

Move 4: Captain's Chair/Hanging Leg Raise

You might not be familiar with the captain's chair, but you definitely should be. It has you positioned in a tall contraption that looks like a chair with no seat. You lift and lower your legs to engage your abdomen — an exercise named the best to target the obliques of the 13 exercises ACE tested. Or try the hanging leg raise. It's a similar exercise and requires less specialized equipment.

1. Hang onto a pull-up bar, or something similar, with your arms straight and feet dangling.
2. Raise your knees until your thighs are parallel to the ground and knees bent at 90 degrees.
3. Avoid swinging your body back and forth. Instead, move slowly and put your feet down to reset if you start swinging too much.
4. Lower your legs until they hang straight down.

Reps: 8 to 10

Read more: Why the Captain's Chair Is Way Better for Your Abs Than Crunches