Lie on your back with one leg bent and one leg straight. Lift the straight leg up in the air so that it is level with the thigh of the bent leg.
Slowly lower without releasing all the way down then raise back up again. Raise for a count of 2 and lower for a count of 2.
Do not let the lower back overarch.
Complete 6-8 reps on each side for 2-3 sets.
Increase reps gradually when you feel able to (aiming eventually for 3 sets of 20 reps)