I have entered a new--active!--phase of physical therapy: strength training.
To warm up at home I still do pendulums, but at my PT's office I use the shoulder bike--a crazy-looking mechanism if ever I saw one, where you pedal with your arms. Most of my effort comes from my right arm. As my PT says, the left arm is "along for the ride."
Do not be fooled: I am still working on regaining mobility. I had quickly regained the first phase of my mobility (0 degrees for external rotation and 90 degrees for forward elevation). Now I am moving past those ranges, and adding other angles as well, to try to bring the joint gradually back to normal. What is even more exciting, I am starting to do these exercises actively. In other words, I use the muscles of my left arm and shoulder to do them, rather than using my right arm to guide, or being guided by my therapist.
But I have also added small stregth-building exercises. For instance, isometric exercises, done against a doorjamb, that will progress towards the regular range of rotator-cuff exercises (external rotation, internal rotation, elbow back, and arm straight out to the side). Also, I am starting to return to cable exercises--again, isometrically, which are performed by holding the arm and shoulder still and inducing stress by stepping with the body.
This all feels like progress.