Hamstrings exercise
Stability Ball Leg CurlHow to do it, with form in numbers
- Main muscles
- Hamstrings
- Also works
- Glutes, Abs
- Equipment
- Stability ball
- Level
- Intermediate
How to do it
How do you do the Stability Ball Leg Curl?
- Lie on your back with your heels and lower calves on the ball.
- Put your arms out to the sides and lift your hips into a straight line.
- Pull your heels towards you, rolling the ball in.
- Keep your hips high, then roll the ball back out slowly.
Cues
- Squeeze your glutes to keep your hips up.
- Shoulders, hips and knees in one line.
- Roll out slowly; do not let the hips drop.
Common mistakes
- Letting your hips sag as you roll the ball.
- Arching your lower back to lift higher.
- Letting the ball wobble off to one side.
Form in detail
What does good form look like?
Starting position
A 65 cm stability ball (the size for a 1.73–1.90 m adult) on a mat. Lie on the back with the backs of the lower calves and heels on top of the ball, feet hip-width apart, ankles slightly flexed (toes towards the shins). Arms out to the sides at about 45°, palms down, head resting on the mat. Brace the stomach, then squeeze the glutes and lift the hips until the body forms a straight line from the shoulders to the heels.
The movement
Keep the hips up and pull the heels towards the backside by bending the knees. The ball rolls in towards the hips and the soles of the feet roll onto it. As the heels come in, the hips rise a little further, so at the end the shoulders, hips and knees form one straight line with the thighs angled up. Pause, then straighten the knees slowly and roll the ball back out, keeping the hips high and level the whole time. Only the shoulders, upper back and arms touch the floor.
End position
Start: knees almost straight, body straight from shoulders to heels. Rolling the ball in until the soles sit on its near side and the knees stay in line with the shoulders and hips needs about 90–110° of knee bend for a 1.75 m avatar; the hips end higher than at the start.
Tempo
1.5 s curl, 0.5 s pause, 2 s roll out, 0.5 s with the legs long (hips still up).
Form in numbers
What are the angles and distances?
| Measure | Target | Good range | Sources |
|---|---|---|---|
| Ball diameter (1.75 m avatar) | 65 cm | 55–65 cm | [3] |
| Feet spacing on the ball | hip width, about 20 cm | 10–25 cm | [1] |
| Arms on the floor, from the body | 45° | 30–90° | [1] |
| Knee flexion at the start | 5° | 0–15° | [1][2] |
| Hip extension at the start (shoulder-hip-heel line) | 0° | −10° to +5° | [1] |
| Hip extension at the end (shoulder-hip-knee line) | 0° | −10° to +5° | [1] |
| Pelvis tilt side to side | 0° | ≤ 5° |
The targets our 3D demo was built to, from the references below. Bodies differ, so treat the ranges as a guide for your own build.
For coaches
Use this demo in your clients’ programs
The Stability Ball Leg Curl is in Trainaq’s exercise library. Add it to a workout, and your client sees this demo in the free Trainaq app above the sets they log.
Sources
