This exercise will improve mobility throughout your spine and hips.
Start by sitting on the ground. Bring your left leg forward with your knee and hip angles positioned at 90 degrees. Bring the right leg behind with your knee and hip angles also positioned at 90 degrees. Position your pelvis and spine upright. You can use a yoga block or other support under your left hand to improve your spinal alignment. Now, using your thigh muscles, press the knee down into the floor and hold this stretch position for 1-2 minutes. Repeat on the other side.