Written for stretching the left piriformis muscle:
Lying on your back with knees bent.
Grasp the left ankle with the right hand. Make sure the left ankle and left foot are just above the right knee as shown below in the photo.
Rotate the left leg until slight tension is felt in the left gluteal (posterior leg) region.
From this point pull with both hands toward the direction of the right shoulder.
Hold for 20-30 seconds and repeat on the other side