Leo rules the upper back and the spine, which means we can certainly benefit from strengthening the muscles in both, the upper and lower back. If you practice yoga regularly, you have probably mastered most of them, but if you still haven't, try to incorporate them into your routine:
Upper Back:
Gentle Twist
Cat Pose
Cobra Pose
Locust Pose
Revolved Triangle
Dolphin Pose
Bridge Pose
Crow Pose
Lower Back:
Chair Pose
Upward-Facing Dog Pose
Upward Plank Pose
Garland Pose
Side Crow Pose
Wheel Pose (my favorite)
Extended Puppy Pose
Namaste!