Leg Curl (Stability Ball)
The Stability Ball Leg Curl is a hamstring-dominant exercise that involves curling a stability ball towards your glutes while maintaining a bridge position. This movement builds posterior chain strength and core stability by forcing you to balance on an unstable surface.
Iridium tracks this as a bodyweight-dependent movement, scaling repetition targets relative to your current body weight to ensure consistent progression. Since external loading is limited, the app relies on RPE trends to gauge intensity and determine when set volume should increase. All accumulated fatigue counts toward your hamstring Maximum Recoverable Volume to prevent this accessory work from impacting recovery for heavier compound lifts.
Form Cues
- Keep your hips elevated and glutes squeezed throughout the entire set
- Dig your heels firmly into the ball to engage the hamstrings
- Curl the ball in until your knees are bent at 90 degrees
- Control the release phase slowly as you roll the ball back out
- Don't let your hips sag towards the floor as you curl the ball in
- Don't hyperextend your lower back to compensate for weak hamstrings
- Don't let the ball wobble side-to-side; keep your core braced
- Don't rush the extension phase; keep tension on the muscles
Common Mistakes
- Sagging hips during the curl
- Relying on momentum to move the ball
- Hyperextending the lumbar spine
- Insufficient range of motion
- Relaxing the core
Muscles Worked
This exercise primarily strengthens the hamstrings through knee flexion while simultaneously challenging the glutes to maintain hip extension. Unlike machine curls, it forces the core and stabilizer muscles to work overtime to keep the unstable ball steady, providing a functional boost to your posterior chain.
Primary
Secondary
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