Doing mild cardio and stretching. Walked fast for 90 minutes today. Also working on flexibility. I had my first day of physical therapy. The Physical therapist who has his PHD said shockingly that he read the notes from the Orthopedic Surgeon but something else is going on in addition to the partially torn rotator cuff. He said I do have a partially torn rotator cuff but my strength in what is still attached is excellent. He said the pain is coming from impingement. He talked at length the tests he did and the symptoms I exhibit. He said the tendon is being crunched and is being inflamed causing a lot of pain. He said the good thing is that MRI shows a partially torn rotator cuff but testing its strength is excellent to reiterate. Seeing this guy three times a week. I will see how it progresses. No lifting for now.
I'm reading everything I can about impingement and lifting. There is a guy on youtube who was the physical therapist for the NY Mets. He's an avid lifter. His site on youtube is AthleanX. I use to watch his videos and thought it was just a gimmick and foolishly disagreed with a lot of what he had to say. Wow, was I wrong. Now from what I have learned from reading, talking to my orthopedic surgeon and physical therapist is that he really makes a lot of sense. So much of what we do in lifting could be improved but we rely on empirical knowledge gained from the champs. Considering how many have wrecked shoulders like Arnold, Zane, Stallone, Draper, Ferrigno, Corney and so many more maybe we can learn something from these new age experts. One thing I won't do again is dumbbell flies for the chest. Better ways to do it with cables and that technique is on the site Athlean X. Another thing that aggravates impingement are stuff like upright rows and dumbbell side laterals for delts. The best way is not to pretend to pour a pitcher of water. Stuff like that are not good for delt health. Seen the best way is to bend over slightly and keep the thumb up and that opens up the shoulder instead of crunching the tendon. Just little tricks of kinesiology matters. Another example is benching. Keeping the elbows out while benching has been called the bodybuilding method to build big pecs. The safer method is to keep the elbows closer to the sides of your body like power lifters do. This old dog is learning new tricks. Just learned a new way to curl that I never thought of. Also learned of new way to train the rear delt that is healthier for the delt. I will save it for another post.
As you are being reminded, our bodies are very complex. Seems like you are in good hands now between your doctor and your physical therapist. My guess is as long as you continue to follow their advice, you'll see improvement in injury caused pain in your deltoids. What you said about dumbbell flies makes excellent sense. I never attempted very much weight doing those. My preference is using a pec deck....similar movement with much less stress on the delts, I would imagine.
My current routine includes upright rows. I do them using cables and very light weight which works for me. I can't manage side laterals using a cable for some reason, so I just use really light dumbbells....like 15 lbs or less. The other day I did them using 7.5 lbs. One might say, why bother. Here's why. I actually felt it, but in a good way not an 'uh oh' way.

No gym for me Saturday, Sunday and today. Saturday and Sunday, not only was my back acting up, so was my gut. Today, I had a board meeting which is held in another city about 50 miles away from 12:00 to 1:00 p.m. After stopping for a French Dip sandwich for lunch on the way home, I was bumping up against commuter traffic. So, keeping my fingers crossed the back and stomach are good tomorrow, because I have nothing else going on that cuts into my gym time.
I weighed 180 lbs. this morning. I actually feel better at 175 lbs. and my clothes fit better. I had cottage cheese, OJ and coffee for breakfast; screwed lunch with the French Dip and fries and going for a light dinner tonight...probably an Evol frozen entrée which is less than 400 calories.