Shoulders are a real bugger. I pulled my collar bone free years ago when I discovered that jumping motocross bikes was harder than it looked. Stretched ligaments. Took months to sort out. Had to sell my GSXR-1100 sports bike because I could no longer handle the aggressive riding position. Now, 20 years later, I still have to have my push bikes with handle bars at saddle height (though age is also a significant factor now) and still get numb hands driving a car. All the physiotherapy and other mucking about did little more than give therapists something to do while all the other funny machines achieved buggerall.