I kayaked last week and found out that I can't do a normal stroke on the left side. Exercising on dry land showed that I have some stiffness and pain when I do the paddling movement, which includes putting my fist forward (holding the paddle), elbow bent, and pulling the bent arm backwards, close to the body. I discovered that I somehow move my shoulder up and make an exaggerated circle with it, because doing it with the shoulder in its normal position causes pulling and slight muscle pain (not joint or bone) in the upper arm and chest. The same pain appears when I try to try a straight punch with the left fist.
I am not sure about the cause, but eight weeks ago I had a bad bruise on the second rip on this side, and I suspect that I might have held the side mostly immobilized for 3 weeks or so until the pain subsided. I massaged myself a bit, and found mild to mid-strong trigger points in the scalenes, supraspinatus, subclavicus, anterior deltoid and lateral pectoral major. The massage reduced the pain and stiffness, but did not eliminate it.
Are there any exercises, with stretching or similar, which will help these muscles go back to normal motion without feeling stiff or painful? A coach suggested shoulder circling and push ups, but I neither feel the stiffnes when I do these, nor do they seem to help. It is a thing which really happens only when the shoulder is down and the arm moves back and forth with bent elbow.