Cat - Cow
Cow pose (top) and cat pose (bottom) are great poses to warm up the spine and begin working the muscles both in the back and front of the body that support and move the spine. Make sure you press your hands firmly into the ground, pressing the ground away from you for both poses.
Sphinx Pose
This pose works the upper back muscles. To get the greatest benefit, line the elbows under the shoulders and press the forearms strongly down into the ground. Think about lifting your chest up towards the ceiling to get more lift.
Locust Pose
Locust pose really starts to work the back muscles, especially if held for a longer time. You don't have to lift the legs but lifting them gives an added bonus of working the glute and hamstring muscles as well. While the pose is pictured with arms in front, you can play around with arm variations.
Seated Spinal Twist (Open)
Twists are great for strengthening the trunk but are more effective if you focus on using your side muscles rather than your arms to force your way into the twist. Pictured is a moderate open twist (twisting away from my standing leg). Even though my arm is against my leg, it isn't forcing my twist deeper than my natural muscular limit.
Gate Pose Variation (Side Crunch)
This is one of my favorite poses for strengthening the side body and some of the muscles deep to the spine in the back. You can hold this position or pulse down and back up an inch or two, repeating 2 or 3 sets of 10. If you choses to dip down, I recommend inhaling down and exhaling as you come up.
Single-Leg Crunch
Like most crunches, this one tones the "ab" muscles. By keeping one leg long and the other flat on the ground, the hips can remain more neutral while you lift your upper body towards your feet, eliminating any discomfort in the low back. You can pulse up and down or stay in the crunched position while you breath.
Bent Knee Crunch Position
This position works the "ab" muscles more than the single-leg crunch, but it can round the low back. If this pose doesn't cause your back discomfort it can be great for building strength. Keep your knees over your hips and try to keep your ankles in line with your knees while you reach your upper body forward.
Sunbird Pose
This pose works the deep stabilizing muscles of the spine - the same muscles that help the body to balance. Start on hands and knees and then work on lifting one arm and then lower it down. Then lift one leg and lower it down. If you are ready for more challenge, lift one arm and the opposite leg at the same time. For more stability, reach forward through your fingers and back through your leg while keeping your belly lifted.
Walking Plank
This pose builds on the sunbird pose, working the same muscles of the core. You can play with lifting one leg at a time (pictured), one arm at a time, or one leg and the opposite leg at the same time. These are challenging! Remember to reach forward through your arm and back through your leg as you keep your belly lifted. Think cat pose.