Did Chest Flies with a 7.5kg DB yesterday and they hurt my shoulders, don't usually do Chest Flies, anyone might know why they hurt? I can do basically and DB/BB press without pain. I also heard a clicking sound in my left shoulder, maybe I'm going too far with ROM?
Dos it hurt when you are the end going down (open) ? If so, try going down slower, rather focus on controlling the downward/open movement than fast. The up/close movement you can do faster (not super fast).
You will notice, that bodybuilding and powerbuilding moves work vastly different. With 5x5 and compound exercises up to now, you didnt need to focus on timing, but with bodybuilding isolation exercises, this becomes key to make them worthwhile, or worth the time to do at all.
For example, think about it like this, for db flies.
1) you start at the top, pause for 1 second
2) go down and do the negative, it should take you lets say 2-4 seconds before you are allowed to reach the bottom.
3) at the bottom, pause for 2 second
4) go up, this can take you 1-2 seconds.
5) repeat step 1 where you pause a second at the top.
The focus is on control, and isolation, not necessarily weight like most guys think. Doing the right weight, instead of heavy as possible, and eating right, will yield amazing results.
That said, my example above is something I just thought up, haven't read about the proper timings for this in a long time, you should read it up imho if you going into isolation exercises. But basically, I think you go down to fast on db flies, and maybe you still do it too heavy, even though I know 7.5kg is not very heavy, on flies I found I can hurt myself too if I rambo them.