HBP/PE2 + iM shoulder pain

I have a serious issue with the Xiaopengs that are the mobility pairs of the pushups. I'm also stuck on the progression but that's just the side effect.

I'm currently doing 4x12 pushups and 5 Xiaopeng forwards with a 2.5kg weight plate. By the fourth set I'm struggling with the pushups and I can barely lift my right arm and it is also painful in the front of my shoulder (my right shoulder being worse than the left). Yesterday I had a session with my PT and she confirmed that the affected area is where the bicep and the pec tendons "overlap", so it's hard to tell which one is problematic (probably both?). The pain is a sharp "wrong" kind of pain, not unlike muscle soreness, but if I stop doing the movement the pain also stops. After a couple of minutes it gets better and I can lift my arms again, do light stretches like table tops (these are excellent btw), and in 2 or 3 days the pain disappears just like muscle soreness.

I was hoping that with time things would improve. However this month I must have been doing too much, because my right shoulder started to move forward out of its socket, like it was before (it took some months of PT sessions to fix this). So I will stop doing Xiaopengs for the time being, and will concentrate on stretching instead. I will also keep doing pushups in a lower rep range (like 4x8), because they don't seem to be problematic in themselves.

My PT raised an important question that I could not answer: what are these exercises good for (the Xiaopengs) and what effect are they supposed to achieve? What are alternative exercises that can achieve the same effect?

I'm able to do 5x15 pushups, if I don't do the Xiaopengs in between. Should I lower the weight to 0.5kg or 1kg and start the progressions again? How much weight is sufficient to progress? Maybe 2.5kg is simply too much at this point? I have been doing these for many months now and just cannot progress beyond 4x12.

I'm afraid this exercise highlighted some fundamental weakness in my shoulder area, so I'm unsure what to do now. I hope there will be some time during the seminar in Stroud when problems like this can be discussed.

@Mark Collins @Wesley Tan 

The xiopengs highlights any mobility problem with the shoulder. The shoulder should be able to circumduct(rotate fully) under load. Functionally this is evident in swimming freestyle and backstroke. 

I also use it as a diagnostic tool to identify any shoulder issues.

I have my patients perform these with no weight with less range of motion and build gradually. You will need to be able to do xiopengs to do shoulder dislocates and eventually swinging on the rings.

You should never be training to the point where you cannot lift the arm unless you like to fatten you PT's wallet.

Thanks Mark - I have much less pain if I raise my arms with my palms facing down or externally rotated (backstroke) with the 2.5kg plate. I'm also fine if there is no or minimal weight. I'm not sure about "dropping" or pulling with my arms in front of me (freestyle)... Could this be some kind of impingement?

Range of motion is not a problem. I have tight lats though, does that make any difference in this exercise?

This movement does not diagnose any particular shoulder injury, it just highlights you have a problem. Your PT would have a better idea after looking and feeling your shoulder.

Tight lats will cause problems in the shoulder.

Thank you Mark, I think I know what to ask my PT when I next see her.

ps. just re-tested shoulder dislocates, I haven't been doing these for some time as I regressed to previous PEs. I was able to do mastery level overgrip, no pain, now it is painful too. Definitely something going on, maybe went too hard with the Xiaopengs too soon. Rest, light stretching and PT sessions to follow for the rest of the summer at least