The human body is a fascinating structure. And part of that fascination is that there are underlying natural asymmetries due to our biology.
We have a liver on the right side of our body and a heart on the left. Most of our organs attach posteriorly and create a tumbling to the left. There is a vortex swirling inside our body moving counterclockwise (to the left). The left hemisphere of our brain is slightly in-front of the right.
All of this leads to our bodies naturally going to the right. Your body will always take the path of least resistance. There is more “stuff” on the left, so the body moves the center of gravity over to the right.
This puts us in right stance (a phase of gait) for many activities. This right stance is shown by a left hemipelvis that is rotated forward (anterior tilt), abducted, and externally rotated. The femur follows the pelvis and is put in compensatory external rotation and abduction. The right side of the body is in more of an internally rotated state at the hip. This creates rotation of the spine to the right, which can be seen as more paraspinal activity on the right. To counterbalance the rotation of the spine to the right, the thorax rotates back to the left. Creating internal rotation of the right anterior ribs and external rotation of the left ribs. Leading to a left shoulder that is higher than the right. THIS IS ALL NORMAL!
The issue occurs when your body forgets how to get out of the right side and into the left side. The inability to create reciprocal motion in the pelvis can create a cascade of issues in the spine, lower and upper extremities. Muscles can only work if they are in the right position to create torque. If you are constantly in right stance, you’ll create shortness of the hip internal rotators and lengthening of the hip external rotators. The hamstring on this side will be short compared to the one on the left that will be long. Both can feel tight, but only one needs to be lengthened. On the left side you’ll have shortness of the external rotators and lengthening of the internal rotators. Because the internal rotators are too long, they can’t create enough torque to shift into the left hip.
Having the ability to shift from side-to-side creates efficient movement with muscles that are in the optimal length to avoid feeling “tight”.