The hamstring stretches are some of the best stretches you can do to protect yourself from a low back injury.
Specific Hamstring Stretches for Back Pain Relief
Hamstring Exercises to Help Your Lower Back - The Southeastern Spine Institute
5 Super Stretches to Loosen Your Lower Back, from a PT
7 Great Stretches for Your Mid-Back
Hamstring Exercises and Stretches to Stay Strong, Flexible, and Injury-Free
Stretches You Should Do Before Getting Out Of Bed
Hamstring Stretch: 6 Easy Ways to Stretch Tight Hamstrings
The Best and Worst Exercises for Back Pain
Are your hamstring stretches effective? — Precision Physical Therapy
The Best 7 Exercises to Strengthen Lower Back
9 Sciatica Stretches to Ease Nerve Pain