Lie on your back with your knees bent, your chin tucked in and your weight supported on both forearms.
Push your pelvis upwards, until your thighs are in line with your spine.
Hold this position briefly and lift one, straightening the leg out and keeping both knees at the same height.
Do not allow your lower back to arch and keep your pelvis level.
Move your knee up and down in a slow and controlled movement.
Keep your pelvis up and repeat on the other side.