Stability Ball Leg Curls (How To, Muscles Worked, Benefits)

The Stability Ball Leg Curl is a hamstring exercise performed lying on your back with the heels elevated on a stability ball, curling the ball toward the body by bending the knees while keeping the hips elevated throughout.

It trains the hamstrings in their primary role as a knee flexor while simultaneously demanding significant glute and core activation to maintain hip height, making it a more complete posterior chain accessory movement than it gets credit for.

With no equipment beyond a stability ball, it’s one of the most accessible hamstring accessory movements available.

Primary Muscles Worked: Hamstrings, Glutes
Secondary Muscles Worked: Core, Calves
Equipment Needed: Stability Ball

How To Do Stability Ball Leg Curls

Step-by-Step Instructions

1. Set-Up:

• Lie flat on your back with both heels on top of the stability ball and legs nearly fully extended.
• Press the heels into the ball and drive the hips up into a bridge position. The body should form a straight line from shoulders to heels.
• Keep the arms flat on the floor at the sides for stability.
• Hold the bridge position before initiating the curl.

2. Execution:

• From the bridge position, curl the ball toward the body by bending the knees and driving the heels into the ball.
• Pull the ball until the knees are bent to approximately 90 degrees or the heels are under the knees.
• Pause briefly at the top with the hips extended and the hamstrings fully contracted.
• Slowly extend the legs back to the starting position, rolling the ball away while maintaining hip height throughout.
• Do not let the hips drop during the eccentric. Keeping the hips elevated for the entire set is what separates a quality rep from a sloppy one.

3. Tips for Proper Form:

• The hips stay up for the entire set. If the hips are dropping on the way out, the hamstrings are fatiguing.
• Drive the heels into the ball rather than just resting them on it. Active heel pressure increases hamstring engagement and helps control the ball through the movement.
• Keep the movement slow and deliberate, especially on the eccentric. The instability of the ball makes it tempting to rush… don’t.

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Key Benefits

• Trains the hamstrings as knee flexors through a full range of motion while simultaneously requiring the glutes and core to maintain hip extension.
• The instability of the ball increases the demand on the stabilizing musculature of the hip and core, adding a neuromuscular challenge that a lying leg curl machine doesn’t provide.
• Develops hamstring strength and control in a position relevant to sprinting and athletic movement, where the hamstrings must function as both knee flexors and hip extensors simultaneously.
• Requires minimal equipment and can be performed anywhere a stability ball is available.

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Modifications and Variations

Easier Option:

• Reduce range of motion and curl the ball only partway in until strength and stability develop enough for a full rep.
• Allow a brief hip touch to the floor between reps to reset if maintaining hip height for a full set isn’t yet achievable.

Harder Option:

• Perform as a Single Leg Stability Ball Leg Curl by lifting one foot off the ball and completing all reps on one leg, dramatically increasing the hamstring and stability demand on the working side.
• Add a 2-3 second pause at the top of each rep with the hamstrings fully contracted and hips fully extended.
• Slow the eccentric to 3-4 seconds to increase time under tension and hamstring control through the lengthening phase.

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Common Mistakes

• Hips Dropping During the Eccentric: The most common breakdown in this movement. Hips must stay elevated for the entire set (on the way out is where most athletes lose position). If it’s happening consistently, reduce the rep count and rebuild from there.
• Rushing the Movement: The instability of the ball demands a controlled tempo. Fast reps on a stability ball produce momentum-driven movement, not hamstring training.
• Insufficient Heel Pressure: Passively resting the heels on the ball reduces hamstring engagement and makes the ball harder to control. Drive the heels in actively throughout the rep.
• Arms Assisting Too Much: The arms on the floor should provide light stability support, not be pressing aggressively into the ground to compensate for a lack of posterior chain strength.
• Losing Hip Height at the Start: Athletes sometimes let the hips sag before the first rep even begins. Set the bridge position fully and hold it before initiating the curl.

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Stability Ball Leg Curl Alternatives

Looking for a substitution for Stability Ball Leg Curls? Here are a couple of exercises you may be able to use in their place.

Need even more options? Check out all my favorite Stability Ball Leg Curl alternatives.

Floor Slider Leg Curls

Floor Slider Leg Curls are where the athlete lies on their back. Legs bent at 90 degrees and heels on floor sliders. The athlete will bridge the hips up, extend the sliders out, and curl back.

Single-Leg Stability Ball Leg Curls

A Single-Leg Stability Ball Leg Curl is where the athlete lies on their back. One leg bent at 90 degrees and the other fairly straight with their heel on the ball. The athlete will bridge the hips up and curl the ball underneath them and then extend back out.

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Reps and Sets Recommendations

For Accessory Work: 3-4 sets of 10-15 reps with a controlled tempo and hips elevated for the duration of every set.

More Links and Info

Looking for more great Lower Body Lifts? Head over to the exercise library where there is a great collection of exercises to help you reach your athletic potential. All for free.

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