You may find some back pain exercises helpful when you have acute lower back pain (a recent back problem that is in the early stages). This exercise is a particularly nice and easy one to do if your back is very sore as it is a gentle stretch.
Of course, always check with your doctor or physiotherapist before starting any program of lower back exercise.
Level - Easy
Lie in your back and let your legs roll gently from side to side. Use your tummy muscles to lift from a strong centre when you bring your knees back to the middle. Go only as far as you are comfortable.