Life taxes the human back and spine. After working with so many clients with lower and upper back pain, I sometimes wonder why we ever stood up as a species. It is truly important to keep your spine both supple and strong. Here is a great series of yoga poses to increase both flexibility and strength. Just click on the link to learn how to get into each pose.

Standing Forward Bend [1] - You can keep your feet together or have them separated so they're under your hips. Just let your torso and head hang, and you can bend your knees slightly to bring more of the stretch into your lower back.
Take a vinyasa [2] to the ground and come into Cobra [3]. Be sure to keep your shoulders relaxed away from your ears and lift your head as high as you can to lengthen through the spine.

Want to see the other stretches? Then

Now stand on your knees so they're directly under your hips and come into Camel [4]. If you want to take this pose even further, try doing Advanced Camel using an exercise ball [5]. After you're done with this pose, take a counter pose for your lower back by doing Child's pose [6].
After stretching your back, take a vinyasa [7] to Down Dog [8] and do a Jump Through [9] so you're lying on your back. Bend your knees and come into Half Wheel [10]. After five or more breaths, repeat this pose, or...
Come all the way up into Full Wheel [11]. Work on bringing your hands and feet a little closer towards each other to increase the stretch even more. Then after five to ten breaths, slowly drop onto your back, hug your knees into your chest and rock over your spine from side to side.
Sit up and release your lower back with a Seated Forward Bend [12].

Fit's Tips: This is a great sequence to do all at once, but ease into it if your back muscles are tight. It may also feel better on your back to do Child's Pose in between each back stretch.

Source [13]