Intermediate

Single-Leg Swiss-Ball Leg Curl

Curling the ball in with a single leg forces one hamstring to handle both knee flexion and the bridge, while the instability recruits the glutes and stabilizers hard. It is a demanding bodyweight progression that exposes and fixes side-to-side imbalances. Master the two-leg version and hip bridge hold before attempting it.

Body part
Glutes, Hamstring
Type
Balance, Strength
Browse by movement
Hinge, Knee Flexion
Muscles worked
Target
Biceps Femoris, Semitendinosus
Secondary
Gluteus Maximus
Tertiary
Erector Spinae, Gastrocnemius Medial Head

How to do it

  1. 1

    Lie on your back with one heel on a stability ball and the other leg lifted off the ball.

  2. 2

    Brace your core and lift your hips into a straight bridge, weight through the heel on the ball.

  3. 3

    Curl the ball toward your glutes by bending the working knee while keeping your hips high.

  4. 4

    Squeeze the hamstring at the top without letting your hips sag.

  5. 5

    Slowly extend the leg to roll the ball back out, staying bridged.

  6. 6

    Finish all reps, then switch legs. Exhale as you curl, inhale as you extend.

Tips

  • Keep the free leg still and your hips level to stop the ball from rolling sideways.
  • Do not let your hips drop as the ball rolls out; keep the bridge locked.
  • Widen your arms on the floor for extra balance while you learn the movement.

Variations

Common mistakes

  • Trying this before the two-leg version is smooth usually ends with the ball shooting out sideways on the first rep. Own ten controlled two-leg curls and a steady bridge hold first.
  • Swinging the free leg to help drag the ball in borrows momentum the working hamstring should be supplying. Hold that knee still, tucked toward your chest or pointed at the ceiling.
  • Letting the heel lose contact as you extend sends the ball drifting away from you rather than rolling. Keep pressing the heel down into the ball, not just pulling it back.
  • Cramp is far more likely here than on the two-leg version, because one hamstring is doing all the hip and knee work. If it grips, lower the hips and stop the set there.
  • Adding these at the end of a heavy hinge session asks a tired hamstring for a hard, one-legged effort. Put them early in your accessory work or on a lighter day.

Frequently asked

How many reps of the single-leg swiss-ball leg curl should you do when you are new to the exercise?
Two or three sets of 5 to 8 per leg is a realistic start, and the honest stopping point is the rep where your hips first dip. If five is out of reach, shorten the roll-out to half the range and add distance as your hips learn to stay up. Progress by adding reps to 8, then by pausing two seconds with the leg straight. Once or twice a week, and give the hamstrings two days before any sprinting.
How do I make the single-leg swiss-ball leg curl easier or harder?
To make it easier, curl the ball in with both legs and roll it out with one, which keeps the demanding half of the rep. Spreading your arms wide on the floor, working through half the range, and resting your hips on the floor between reps all help too. To make it harder, cross your arms over your chest, pause for two seconds with the leg extended and the hips high, take four seconds to roll out, or raise your shoulders onto a low step so the hips travel further.
What is the single-leg swiss-ball leg curl for and who should skip it?
It asks one hamstring to bridge the hip and bend the knee at the same time while the glutes and stabilizers fight the ball, so it builds one-sided hamstring strength and control with no equipment beyond a ball. It suits athletes and home trainers who already handle the two-leg version. Skip it if the two-leg curl still wobbles, if your hamstrings are sore, or in the days before a sprint or field session, since it is demanding in a lengthened position.

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