In this article, we look at five of the most efficient BOSU ball ab exercises that when done consistently will enable you to quickly strengthen your core and tone your abdominal muscles and obliques.
The BOSU ball differs from a traditional fitness ball in that it is flat on one side with a dome on the other side. It can be used with the flat side down or on top, depending on the exercises you want to do.
The ball’s unique shape creates an unstable workout platform which forces the user to make constant small adjustments to stabilize themselves. Done regularly, this movement helps to improve stability, mobility, reflexes, muscle tone, and more.
To find out more about the BOSU ball and what it can do for you, click this link.
Any exercise done on a BOSU ball will tone your core.  The BOSU ball ab exercises below are among the most effective you can do if you are looking to shape and tone your abs, obliques, and mid-section. They will also target your upper and lower body, though to a lesser extent.
Start with 10 repetitions of each exercise (other than the Plank exercise, which you should do once or twice to start). Increase this to 15 to 20 reps as your strength improves, building to two or three sets, being sure to keep your abs contracted throughout each sequence..
BOSU ball ab exercises can be customized to your fitness level.  For example, to make the Crunches more challenging, hold a light weight in each hand while doing them. If you find it difficult to keep your balance when doing Side Planks, instead of stacking your feet, put one foot on the floor in front of the other.
BOSU Ball Ab Exercises
Most of the BOSU ball exercises for abs on this page are variations of two of the most popular ab exercises, these being the Crunch and the Plank. Doing these on a BOSU ball will increase their effectiveness and make doing them less of a chore. The ball will also provide a degree of support for your back.
1. Crunches
Place your BOSU ball on the floor with the domed side on top. Â 
Sit on the ball with your knees and elbows bent, then lean back, allowing your back to rest across the ball.
With one hand on either side of your head and your elbows pointing out to the sides, lean forward slowly, crunching your abs as you do.
Slowly release the contraction as you recline back to your starting position.
2. Side Crunches
Put your BOSU ball on the floor with its domed side up and bend your feet towards your buttocks so that you are sitting on the floor with your right side leaning across the ball.
Place your hands on either side your, then lift your upper body into a Crunch, keeping your elbows opened out to either side and not letting your chin touch your chest.
Lower your upper body to your starting position. Repeat for the desired number of reps, then swap sides.
3. Opposite Arm and Leg Raise
Place your BOSU ball on the floor with its flat side down, then lie over the dome so that it cradles your lower back.
Lift your right hand above your head, and rest your left hand on your stomach.
With your left foot on the floor and your left knee bent, extend your right leg out to the front.
Do a Crunch, reaching your right hand in the direction of your left leg, then return to your starting position. Repeat, alternating sides.
4. Bicycle Crunches
Place your BOSU ball on the floor with the domed side facing upwards.
Sitting on the ball with bent knees, lean back so that your back is resting on the ball.
Bend your elbows, and position one hand on either side of your head.
Lift your feet off the ground so that your knees and waist make a 90-degree angle.
Bring your left knee up towards your chest, straightening your right leg out in front of you and rotate your right shoulder to bring your elbow towards your left knee. Repeat this movement, alternating sides.
5. Supine Open and Tucks
Place your BOSU ball on the floor, flat side down.
Sit on the dome with your hands on either side of the ball, slightly behind you.
Contract your abs, and with your knees slightly bent, lift your feet and legs up towards your chest so that your upper and lower body make a “V” shape.
With a straight back and your neck in a neutral position, stretch your legs out to the front and slowly lean back to return to your starting position.
6. Planks
Put your BOSU ball on the floor so that the flat side is facing upwards. Â 
Kneel on the floor and place your forearms on the platform.
Contract your core and lift your knees, balancing your weight on the underside of your toes and your forearms.
Maintain this position for thirty seconds, or as long as you can, contracting your abs the entire time.
7. Extreme Planks
For this exercise, you will need to put your BOSU ball on the floor with the flat side facing up. You will also need a stability ball which should be placed approximately four feet from the BOSU ball.
Place your forearms on the BOSU ball and your feet on the stability ball.
Get your balance and contract your core muscles.
Hold this position for at least 30 seconds.
8. Twisting Planks
Place your BOSU ball on the floor with the domed side down.
Get into a plank position with your hands on the outsides of the ball directly under your shoulders.
Contract your abs muscles, then bend your right knee bringing it up and under your body towards your left shoulder.
Return to a plank position, then reverse sides.
9. Knee to Elbow Planks
Place your BOSU ball on the floor with the flat side down.
Get into a plank position with your elbows on the ball’s dome.
Bring your right knee up and out to the side lifting it towards your right elbow, then return to your starting position.
Swap sides, working your left leg.
10. Side Planks
Put your BOSU ball on the floor, flat side down.
Assume a plank position (as in the previous exercises), but instead of being face down you will be on your side. Balance your right elbow on the ball, keeping it directly beneath your right shoulder.  Your left foot should be lined up with and on top of your right foot.
Keeping your hips lifted off the floor and your body in a straight line, hold this position for 30 seconds or as long as you are can. Repeat the exercise, working your left side.
BOSU Ball Ab Exercises Summary
If your core, waist, and belly isn’t as toned as you would like it to be, give the above BOSU ball ab exercises a try. Do them at least two or three times a week, and you will soon be rewarded with a stronger core and a trimmer waist and abs.
