stretch lower back how?

My lower back is really tight and my abs are very weak. This is a disaster waiting to happen.

So... the tight back and weak abs makes it hard to do any serious situps. It hurts the back and the hip flexors do all the work. I was thinking if there is a way to stretch the lower back maybe I can work the abs better.

How do I do it?

touch your toes to stretch your back.

also stretch your hip flexors.