Lie on your back.
Bend one leg upwards, placing the foot on the floor.
Draw your other leg up to the same position, maintaining a hips width between your legs.
Lift one foot slightly off the floor.
Using the effort of your remaining foot, lift your hips up into a bridge until you have a straight line from your shoulders to your knees.
Lower back down and repeat.
Keep your pelvis level throughout this exercise.