Lie supine (on your back) on the floor with your lower legs on a stability ball.
Extend your arms out to your sides for balance and support.
Raise your hips and lower back off the floor so that your body is straight.
Keeping your hips and back straight, exhale as you flex your knees and roll the ball towards your back with your heels. Your feet should roll onto the top of the ball and your body should lift further off the floor.
Inhale as you roll the ball back to the starting position by extending your knees.
Repeat for the prescribed number of repetitions.
Comments and tips
Keep your back and hips straight. Only your lower legs should move.
Since you only use your body weight and can’t significantly increase the amount of weight that you use with the stability ball leg curl, it isn’t useful after a certain point for building muscle and strength.
Thereafter, you can make the stability ball leg curl more difficult by doing it with one leg.