Lie on your back and bring your legs up to a table-top position with your hips and knees at a right angle.
Place a ball between your knees and apply gently pressure to hold it in place.
Contract your abdominal and trunk muscles as you extend both legs down towards the floor, whilst squeezing the ball between your legs.
Bring both legs back up to the table top position and repeat.
Ensure you keep your core strong and back flattened to the floor throughout this exercise.
