Exercise guide
Crunch - Legs On Exercise Ball
This crunch variation places the lower legs or feet on an exercise ball with the knees bent near 90 degrees. The abdominals lift the shoulder blades while the ball supports the legs. The unstable surface also requires the feet and hips to keep the ball from rolling.
Training context
Before adding the exercise-ball crunch
Choose a ball size that allows the knees to remain comfortably bent while the back rests flat on the floor. The ball should sit on a nonslip surface with enough open space around it.
The goal is a short upper-body curl. Pressing aggressively through the feet can cause the ball to move and distract from the abdominal work.
Technique overview
Keep the ball still as the shoulders rise
Rest the legs securely on the ball and place the hands lightly beside the head. Curl the shoulder blades a few inches from the floor without pulling the neck or pushing the ball away. Pause briefly, then lower slowly. Reset the feet whenever the ball changes position.
Treat this as an overview and use a range, pace, and setup you can control.