How to Do Stability Ball Knee Tucks

Proper Form, Variations, and Common Mistakes

stability ball tucks

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Also Known As: Stability Ball Reverse Curls

Targets: Abdominals, Shoulders, Chest, Triceps, Hips

Equipment Needed: Stability Ball, Yoga Mat (optional)

Level: Advanced

The stability ball knee tuck is one of those abdominal moves that looks like it's fun to do. You essentially perform a plank with your legs balanced on the stability ball, then you tuck your knees forward toward your chest, drawing them close as you roll the stability ball toward you. The move certainly can be fun (if you define fun as challenging) but you must have enough core, chest, and shoulder strength to perform the exercise with the appropriate form. It's a good idea to be able to hold a plank with your legs balanced on a stability ball for at least 30 to 60 seconds before attempting the move.

In addition to strengthening the major muscle groups of your abdominals, the stability ball knee tuck develops strength through the stabilizing muscles of your spine, shoulders, and even your hips. Together, when these stabilizing muscles are strong, you're less likely to experience undesirable movement at the major joints, helping prevent injuries caused by excessive mobility or lack of stability. You're also going to experience more coordinated, fluid movement during everyday activities, like bending over to pick a toy up off the ground, or carrying unequally-weighted grocery bags with each arm.

You can incorporate the stability ball knee tuck into just about any strength training routine. Core work can be added to the beginning or end of just about any strength training or cardio routine for a well-balanced exercise program.


Stability ball knee tucks are a more advanced ab exercise designed to target the major muscle groups of the core (abdominals and back), while also targeting the stabilizing muscles of the chest, shoulders, and hips. Also, because the exercise requires you to hold a high plank position while using your legs to roll a stability ball to and from your torso, your triceps engage to help you maintain the proper position while your quadriceps engage to keep your body steady as the ball rolls. All-in-all, the movement hits almost the entire anterior chain (the front half) of your body, while placing a primary focus on the muscles of the abdomen and low back.

For regular exercisers looking for a challenge, the stability ball knee tuck is a perfect option for stepping up ab day. By adding instability to your routine, you're forcing your body to engage the small, stabilizing muscles of your shoulders and hips, strengthening areas that are often neglected. Trained regularly, strengthening these muscles can help with day-to-day movement, making you more agile and less prone to falls or injury.

Additionally, the exercise develops anti-rotational core strength. In essence, this means your core has to work to prevent from rotating in an undesirable way. Because the stability ball can roll side-to-side in addition to front-and-back, your hips, abdominals, and spinal erectors are forced to try to prevent the side-to-side motion as you draw your knees toward your chest. Developing anti-rotational core strength can transfer to day-to-day activities, preventing your spine from moving undesirably when you go about daily life. For instance, if you step off a curb or trip on the sidewalk, your core is better prepared to engage and protect your spine from moving strangely, ultimately helping prevent low back pain or injuries.

Step-by-Step Instructions

The stability ball knee tuck requires enough space for the length of your body to fully extend—roughly the length of a yoga mat. If desired, place a yoga mat on the ground to help cushion your palms. Set the stability ball at one end of the mat before getting into the starting position for the stability ball knee tuck.

  1. Get in a "tabletop position" on your yoga mat with your knees positioned on the mat under your hips and your hands positioned on the mat under your shoulders, the stability ball behind your feet. Check your form here—your body should form a straight line from your tailbone to the crown of your head. Engage your abdominals, pulling your belly button toward your spine.
  2. Place one leg at a time on top of the stability ball, so that the ball is positioned somewhere between the top of your feet (at the ankle joint) and the top of your shins (without interfering with your knees' ability to bend). The closer to your body the ball is, the easier it will be to maintain your balance. Also, adjust the width of your legs as needed. The closer your feet are together, the more challenging it will be to maintain your balance. Separate your legs slightly for greater stability.
  3. Take a breath in when you feel sufficiently balanced, and check your form to make sure your core is engaged and your body is forming a straight line from heels to head. maintain your shoulders over your wrists for the entirety of the movement
  4. Press your feet and shins down into the stability ball and use your abs to help draw the ball toward your chest as you bend your knees and tuck your lower body up to your torso. Bring your knees as close to your chest as you comfortably can. Exhale as you draw your knees forward.
  5. Hold for a second, then extend your knees, rolling the stability ball away from your torso to return to the full plank position. Exhale as you roll the ball away from you.
  6. Complete a full set of repetitions, then carefully remove one leg at a time from the stability ball, bringing your knees back to the yoga mat. From the tabletop position, rise to kneel, then stand.
  7. The slower you go, the more controlled and advanced this movement will be.

Common Mistakes

Allowing Your Shoulders and Neck to Sag

When stability ball knee tucks are done with correct form, you should hold a perfect plank position with your legs balanced atop the stability ball. This is even more challenging than performing a plank with your legs on the ground due to the instability that the ball adds to the exercise. As a result, it's very common for people to focus on keeping their legs steady while completely ignoring the form of their upper body.

If you allow your neck to hang down between your arms, or if you allow your chest to "collapse" between your shoulders, failing to engage the stabilizers of your chest and shoulders, you're setting yourself up for possible injury. Once you've balanced your legs atop the ball, check your upper body. Make sure your neck is neutrally aligned so your body is forming a straight line from head to toe, and fully engage your shoulders, as though you were pressing up to the top of a pushup.

Allowing Your Hips to Drop

Like the issue with your head and neck, if you're struggling to maintain your balance on top of the ball, you're more likely to forget to engage your hips, low back, and abdomen, which could cause your hips to drop and your low back to sag. Given that this is an abdominal exercise, you want to make sure you're properly engaging these muscle groups. Plus, if you allow your hips to drop, you're setting yourself up for a possible low back strain.

The most important thing is awareness—once you've established balance on the ball, lift your hips slightly as you engage your abdomen and draw your belly button toward your spine. Done correctly, this will actually help you maintain proper balance. Check your form in the mirror if you have access to one—before you start the knee tucks, your body should form a straight line from head to toe.

Positioning the Ball Too Far Away From You

As long as the apex of the stability ball is positioned somewhere between the top of your feet and the top of your shins, technically, you're performing the exercise with correct form. That said, the farther the ball is from your knees, the more challenging it will be to maintain your balance.

For people just starting out with the move, it's important to start with the ball closer to the tops of your shins than to your feet. This enables you to master the movement with greater stability before eventually positioning the stability ball farther down your legs.

Positioning Your Feet Too Close Together

While there's nothing wrong with keeping your feet and legs together on top of the ball, this narrow-legged position does make the movement more challenging. Just as positioning the ball farther down your body makes it harder to maintain your balance, a narrow "stance" also makes balance more difficult.

Try separating your feet slightly—roughly hip-distance apart—when starting out. This broader "base of support" makes it easier to keep the ball moving in a straight line as you roll it to and from your body.

Moving Too Quickly

As much fun as it may seem to roll the ball back and forth like a speed demon, moving too quickly increases the likelihood that you'll lose your balance and fall off the ball. A slow and steady pace helps ensure you're focusing on engaging the deep muscles of the core, low back, and hips—the ones you want to engage during this exercise—without having to rely too much on extraneous muscles (quads, shoulders, triceps, chest) to help you maintain your balance.

Try counting as you roll the ball toward you and away from you, aiming to take at least two to three seconds for each phase of the movement.

Modifications and Variations

Need a Modification?

The best modification for stability ball knee tucks is the stability ball plank. Being able to master and hold a perfect plank while balanced with your legs on the ball is the perfect precursor to the rolling version of the exercise. Set up just as explained above, starting in a pushup position, hands on the ground beneath your shoulders. Place one leg at a time on top of the ball with your feet roughly hip-distance apart. Check your form to make sure your body forms a straight line from heels to head. Hold the position as long as you can, aiming for at least 30 seconds. I

f your form suffers at any point, release the position, rest, then try again. It's better to build up your time on the ball slowly with perfect form than to compromise form for the sake of hitting a time goal.

Up for a Challenge?

When you're just starting out with the exercise, the best way to make it harder is to adjust the ball's starting position in relation to your body if you want to increase the balance challenge. First, gradually move the ball farther away from your torso. If you start with the ball at your mid-shins, adjust its starting position so it's closer to your ankles. Next, adjust your "stance." If your feet start about hip-distance apart atop the ball, bring them closer together.

If you're looking for an even greater challenge, try the stability ball pike. You start in the same position as the knee tuck, but instead of drawing your knees toward your chest, you draw the ball toward you as you lift your hips, piking them up toward the ceiling as you keep your legs straight.

Safety and Precautions

Improper form and moving too quickly are the prime things that lead to injuries when performing the stability ball reverse curl. Pay close attention to your form throughout the exercise and keep a slow and steady pace as you draw the ball to and from your torso. Also, consider what type of surface you place the ball on. Slippery surfaces, like tile or treated concrete, may cause the ball to "pop out" from under your feet. Put down a yoga mat for extra traction, or choose a surface with greater friction, such as carpet or grass.

Finally, if you have shoulder, wrist, or low back pain, this exercise may exacerbate the issue. If you feel any sharp or shooting pains while performing the movement, stop the exercise. A crunch or the dead bug exercise might be more appropriate options that target the same general muscle groups.

Try It Out

Incorporate this move and similar ones into one of these popular workouts:

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