Left Pec Muscles and Right Shoulders: Restriction Causing Restriction

The Postural Respiration manual has a section devoted to Left Pec Inhibition. It was one of the last topics that I understood in the grand PRI hierarchy of understanding. Tight left pecs often restrict right shoulders movement. Tight left pecs often restrict left shoulders, too, but I'm concentrating on the right shoulder in this video. But why do pec muscles get tight and overactive? Bench pressing too much? Maybe, but not that's not the biggest issue. The pecs get tight and overactive, in particular the left pec and the right pec minor, when we become "ungrounded" and use our neck to breathe. The typical right BC pattern results in overactive pec muscles. They also get tight when our spine exists in a state of extension, we lose our ability to rotate our spine, and our arms stop swinging (PEC pattern). Once the left pec is tight, or simply overactive, it must be inhibited so that we can move our center of mass to the left, shift into left AF/IR, establish a left ZOA, and open the right side with air. At that point the right arm can move backwards in an unrestricted manner.