Morning glory exercise

It's an exercise for lower back or spinal erectors. Find a long stick or a light barbell and put it on your shoulders spreading the arms wider and grasping the bar. Bend forward with your knees slightly flexed until your upper body becomes parallel with the ground. And then come back to the normal standing position. Do it in three sets, first for 15 times, then 12 and last for 8. I will recommend a barbell because you can increase weight on it. Don't put weights on the first day it will be difficult for you but second day onwards try to put on some.
This will strengthen your lower back which provides you the support for the whole day.

Hey Eva,
Avantika is right. It would target your most of back muscles. Make sure that you keep your knees a bit soft so as to avoid stressing your knee joints.