How to Do Stability Ball Knee Tucks: Proper Form, Variations, and Common Mistakes

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.

How to Do Stability Ball Knee Tucks

The stability ball knee tuck requires enough space for the length of your body to extend fully—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.

To begin, get in a tabletop position on your mat, with your knees positioned under your hips and your hands under your shoulders. The stability ball should be 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.

1. 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.
2. Take a breath in when you feel sufficiently balanced, and check your form to make sure your core is engaged and your body forms a straight line from heels to head. Maintain your shoulders over your wrists for the entirety of the movement
3. 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.
4. 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.

Complete a full set of repetitions, then carefully remove one leg at a time from the stability ball, bringing your knees back to the mat. From the tabletop position, rise to kneel, then stand. The slower you go, the more controlled and advanced this movement will be.

Benefits of the Stability Ball Knee Tuck

Stability ball knee tucks are a more advanced ab exercise that targets the major muscle groups of the core (abdominals and back). Also, your triceps engage to help you maintain the high plank position, while your quadriceps engage to keep your body steady as the ball rolls. So the movement hits almost the entire anterior chain (the front half) of your body.

This move also targets the stabilizing muscles of the chest, shoulders, and hips. These areas are often neglected, but when the 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. Strengthening these muscles can help with day-to-day movement, making you more agile and less prone to falls or injury.

Additionally, this 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 from side to side in addition to forward 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 incorrectly 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, ultimately helping prevent low back pain or injuries and improve sports performance. This list of best core workout equipment offers a wide variety of tools for getting and keeping your core in shape.

Other Variations of the Stability Ball Knee Tuck

You can perform this exercise in different ways to meet your skill level and goals.

Stability Ball Plank

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 ideal precursor to the rolling version of the exercise.

Hold the position as long as you can, aiming for at least 30 seconds. If 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.

Stability Ball Pike

If you're looking for an even greater challenge, try the stability ball pike. In this version, instead of bending your knees and tucking them under your torso, you lift your hips toward the ceiling, keeping your legs straight.

Common Mistakes

Watch out for these common errors when performing this advanced exercise. It's important to do the knee tuck with good form to make it safer and more effective.

Sagging Shoulders and/or Neck

You'll need to hold a perfect plank position with your legs balanced atop the stability ball to do this exercise correctly. It is more challenging than performing a plank with your legs on the ground due to the instability that the ball adds.

Many people focus on keeping their legs steady while ignoring their upper-body form. If you allow your neck to hang between your arms or 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 push-up.

Dropped Hips

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 correctly engaging these muscle groups. Plus, if you allow your hips to drop, you could strain your low back.

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 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

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.

To start, keep the ball closer to the tops of your shins than to your feet. This enables you to master the movement with greater stability. Eventually, you can position the ball farther down your legs.

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 makes 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

Rolling the ball in and out too fast 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.

Safety and Precautions

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:

• Ball Workout for Balance, Stability, and Core Strength
• Abs, Hips, and Thighs With the Exercise Ball and Medicine Ball
• Advanced Ab Workout for Super Core Strength