Single Leg Extension (on stability ball)
- Músculo objetivo
- Hamstrings
- Músculos sinergistas
- Gastrocnemius, Sartorius
- Equipamiento
- Stability ball
- Parte del cuerpo
- Thighs
- Tipo
- Strength
The Single Leg Extension on a stability ball is a single-leg bodyweight curl that targets the hamstrings through both knee flexion and hip extension, with the gastrocnemius and sartorius assisting the knee bend. You lie on your back with one heel on the ball, hold your hips off the floor, and roll the ball in and out with that leg alone. It builds posterior-chain strength, exposes side-to-side imbalances, and adds a constant hip and core stability demand a machine curl cannot.
Cómo hacer el Single Leg Extension (on stability ball)
- 1Lie flat on your back on the floor with your arms at your sides, palms pressed down for support.
- 2Place one heel on top of the stability ball with that leg straight, and hold the other leg off the ball with the knee bent toward your chest.
- 3Press the working heel into the ball and lift your hips off the floor until your body forms a straight line from your shoulders to that heel.
- 4Brace your core and keep the pelvis level and square — do not let the non-working side drop.
- 5Curl the ball toward your glutes by bending the working knee, rolling it in with your heel while keeping your hips high.
- 6Pause when your heel is under your knee and the shin is vertical, holding the hips elevated.
- 7Extend the leg slowly to roll the ball back out to the start, resisting the roll rather than letting it run away.
- 8Complete all reps, lower your hips to the floor under control, then switch legs and repeat.
Consejos de técnica
- Drive through the heel rather than the arch or the ball of the foot — heel pressure keeps the hamstrings and gastrocnemius loaded and stops the ball squirting out from under you.
- Keep the pelvis level and square to the floor; if the non-working hip drops or rotates, shorten the range of motion until you can hold it steady.
- Control the extension at least as slowly as the curl — the eccentric is where most of the hamstring stimulus comes from.
- Press your arms and palms flat into the floor to widen your base and limit sideways roll.
- Own the two-leg stability ball leg curl before moving here; taking one leg away roughly doubles both the load and the balance demand.
Errores comunes
- Letting the hips sag toward the floor mid-rep — this drops the hamstrings out of hip extension, kills tension, and shifts load onto the lower back.
- Rolling the ball in with momentum instead of curling under control — this cuts time under tension and often ends with the ball shooting out from under the heel.
- Resting the ball under the calf or ankle instead of the heel — the contact point moves toward the knee, shortening the lever the hamstrings work against and making the ball harder to steer.
- Letting the ball drift sideways — lateral drift means the working hamstring is no longer pulling in a straight line and the hip stabilizers are failing, which is the usual way people roll off the ball.
- Holding the breath throughout the set — this raises blood pressure and reduces core stability; exhale as you curl the ball in, inhale as you extend it out.
Preguntas frecuentes
What muscles does the Single Leg Extension on a stability ball work?
The primary muscle is the hamstrings, which work through both knee flexion as you roll the ball in and hip extension as you hold your hips off the floor. The gastrocnemius and sartorius assist with knee flexion, and keeping a single hip elevated adds a continuous hip and trunk stability demand.
How is this different from the two-leg stability ball leg curl?
The movement is the same, but one leg carries the entire load and the whole balance task. That removes the symmetry crutch of the two-leg version, so any strength difference between sides shows up immediately. It is the standard progression once you can control the two-leg curl with your hips locked high.
What should I do with my non-working leg?
Hold it off the ball with the knee bent toward your chest, or extended toward the ceiling if you prefer. Resting it on the floor turns the exercise back into an assisted two-leg curl, which defeats the purpose of the single-leg version.
How many sets and reps should I perform?
A practical starting point is 2–3 sets of 8–12 reps per leg. Prioritize control and a level pelvis over rep count — end the set when the hips start to sag or the ball begins drifting sideways.
Can I do this exercise if I have lower back pain?
The lower back usually takes over when the hips sag, so keep them high and stop the set once you cannot. If you still feel discomfort, shorten the range of motion or return to the two-leg version, and consult a qualified professional if pain persists.
