Best Abdominal Exercises You've Never Heard of

Regardless of what type of training you do, repeating the same workouts over and over can become boring very quickly. It's important to add in new exercises every once in a while to keep your workouts fresh, interesting and challenging. You're much more likely to put effort into a workout that you enjoy rather than the same old routine.

In fact, a group of scientists from the University of Florida published a study in which they found that switching up cardio exercises every two weeks made people much more likely to stay motivated to work out.

There are a lot of great ab exercises out there but a lot of them tend to be rather robotic. Take the sit-up for example: you roll up and down, only moving in one direction, for a certain amount of repetitions. The ab muscles are incredibly dynamic. You have four different ab muscles and each plays a different role so you should do multiple motions to get the most out of your abdominals.

You've probably heard of sit-ups, crunches and planks. You may have even heard of the dead bug or leg raises, but you've probably never heard of these four amazing ab exercises.

1. Medicine Ball Dead Bug

This exercise involves balance, coordination and lots of abdominal strength. Dead bugs not only work your rectus abdominis -- the six-pack muscle -- they also work the obliques and transverse abdominis, according to this study in the Zahedan Journal of Research in Medical Sciences.

HOW TO DO IT: Start lying on the floor on your back. Put your left leg in the air with your left knee bent at a 90 degree angle. Your right leg is straight and flat on the floor. Take a light medicine ball, no more than 10lbs, and hold it against the top of your left thigh with both hands.

Take your right hand off the medicine ball but keep holding it against your left thigh with your left hand. Bend your right arm and press your right elbow against the medicine ball so that it is squeezed between the top of your left thigh and your right elbow.

Take your left hand off of the medicine ball. Make sure that you are squeezing the medicine ball with your left leg and right elbow or else it will fall down. Reach your left arm up over your head until it is flat on the floor. Your head, shoulders, and right leg should also be flat on the floor.

With the medicine ball still trapped between your right elbow and left thigh, slowly lift your left elbow and right thigh up to trap the medicine ball. Secure the ball between your left elbow and right thigh and reach out your left leg while your reach your right arm overhead. The goal is to keep the medicine ball about a foot above your body while switching between your left elbow/right thigh and right elbow/left thigh. Move slowly and try not to let the ball slip down towards your body.

2. One-Leg, One-Arm Dumbbell Row

The key to this exercise is to make your core as stiff as possible, like you're doing a plank.

HOW TO DO IT: Grab a light dumbbell — under 20 pounds to start. Get into a push-up position, with the dumbbell in your left hand. Raise your right leg into the air. Once you are balanced in this position, row the dumbbell in your left hand up until it touches your chest, then lower it back down.

Row the dumbbell at least six times, keeping your right leg in the air the entire time. Switch the dumbbell to your right hand and raise your left leg in the air. Perform at least six reps on that side as well.

3. Dumbbell Pullover Crunch

This move is a combination of a leg raise and crunch to work the upper and lower region of your abs.

HOW TO DO IT: Get a dumbbell between 15 and 50 pounds. If you're unsure what weight to use, start at 15 and work your way up. Holding the dumbbell against your chest, lay down on a bench. Raise your legs in the air with your knees bent at a 90 degree angle. Grip the dumbbell under the weight itself, instead of the handle.

Use two hands to hold the dumbbell securely. Press the dumbbell up towards the ceiling until your elbows are locked out and the dumbbell is over your chest. Make sure your head is flat on the bench. Reach your arms backwards with the dumbbell in your hands until your arms are parallel with the floor.

While you are lowering your arms, lower and straighten out your legs until they are parallel to the ground as well. Once your arms and legs are straight out, start to raise them back towards the starting position.

Once you reach the starting position, perform a crunch by rolling your hips back until your butt is off the bench. At the same time, roll your shoulders, head and neck off of the bench. You should be crunching your upper and lower body in towards your stomach. Try to perform 10 repetitions.

4. Side Plank Crunch

This exercise will challenge every muscle on the side of your torso, from your shoulders to your hips. According to a study in the International Journal of Sports Physical Therapy, the side plank is also one of the best exercises out there for your gluteus medius on the outer buttocks, so this exercise has a lot of bang for the buck.

HOW TO DO IT: Start in a side plank position on your right side with your right elbow under your right shoulder and your feet stacked on top of each other with your left foot on top. Keep your knees straight and hold your head held in line with the rest of your body so that you have a tall posture. Make sure that your hips aren't too far backwards; everything should be in a straight line from your head to your ankles.

Drop your hips down towards the floor being careful not to go all the way down to touch. Make sure that you move only your hips. Raise your hips as high as you can, being careful that your elbow and your feet don't move. Perform the hip raises five times, then repeat on the left side.