The pelvis and thorax are connected by the lumbar spine and the abdominal muscles. Because of this, imbalances in either one of these structures will lead to imbalances in the other. To feel how this works in a yoga pose, come into utkatasana (the chair pose). Consciously curl your tailbone upward like Donald duck and notice how your ribcage begins to flare upward and outward in the front. Next, tuck your tail strongly under, and notice how your ribs naturally draw inward toward the central axis of your body.
Since changes to pelvic positioning invariably affect the ribcage, we think of the torso and pelvis as being one connected unit and use one energetic line to position both of these structures rather than working with each individually. The line of energy that we use to accomplish this is called the pelvic/thoracic line. Specifically, this line of energy is used to shorten the space between the first and second sacral and 12th thoracic vertebrae while we practice many of our yoga poses.
Within the context of a yoga practice, the pelvic/thoracic line can be used to experience instantaneous changes in range of motion when forward folding, side-bending and twisting. Additionally, since balancing the weight of the ribs and pelvis along the central axis will help your body retain firmness and straight lines without weakness, you will find that utilizing this line in your practice will increase your endurance, improve your sense of balance and make vertical postures like the tripod headstand much easier to hold.
To experience how the pelvic/thoracic line affects your yoga poses, try the following exercises:
Imagine that your pelvic bowl were the rim of an ice-cream cone. In lordotic posture, the frontal edge of the cone tips downward which puts pressure on the abdominal muscles and causes the belly to protrude. To balance the pelvis, imagine tipping the front of the cone upward to a level position to allow the ice-cream to fall back into the rim. Imagine a cherry dropping down from the level of the solar plexus to center in the middle of the ice-cream. Finish by extending upward through the crown of your head. (adapted from Dr. Lulu Sweigard).
Balance your pelvis and ribs in Warrior 2
Imagine that the space between your zipper and two bottom ribs were like an open clamshell. Close the clamshell ¼ to 1/2 of the way or until the pelvis and ribs balance vertically and horizontally as close to the axis as possible.
Deepen your range of motion in Janusirsasana
Fold forward into Janu Sirsasana with your left leg extended forward. Slide your left leg backward and into the body, much like you were sliding a drawer into a dresser. Next, consciously shorten the space between the mid-front of your pelvis and your solar plexus by imagining that those two points were connected by a thick cable. “Shorten” the cable by simultaneously rolling your tail gently under and drawing your two bottom ribs on the front body inward toward the central axis until your feel your abdominal muscles contacting. Lengthen along your central axis by pulling your head toward your toes. Take note of any increases in range of motion.
NB: Since identifying the exact location of the 12th thoracic and 1st and 2nd sacral vertebrae can be challenging, feel free to simplify by using the belt buckle and solar plexus as your reference points as you practice.