This is the video I used to strengthen my back muscles and learn how to bend at the hips instead of the lower back.
I would do this once a day usually at night after work.
Then the next morning when I did my yoga practice try to find the same movement and sensation.
As you can see in the video they are doing modified sections of Sun Salutation A and B.
They do the first part of Uttanasana but because of physical limitations they don't go all the way.
Heres is an easier version of the one above.