Although I can workout the other muscles effectively, with this one I'm really struggling. Each time I try some exercise I feel pain in my shoulders and I've to stop.
As far as I understand the serratus protracts the scapula, but I generally feel the upper pecs and delts contracted.
So there are some bulletproof exercise for this muscles?
Incline shoulder raise seems to be the best option. The same link lists clap pushups and depth pushups as good plyometric options, since, from your comments, that seems like it's more in line with your current exercises.
Alternatively, the sarretus is involved as a stabilizer in most anterior deltoid exercises, like the over head press. There are a lot of programs (like SL 5x5) organized around the idea that small muscles like this should be trained only as stabilizers in larger, compound, functional exercises, like the press.
reading your question give me a hint that you are going through a hard pull muscle or some bone minor fractions ..
This is usual and just a advice that many people develop such type of things while doing exercise it remain unnoticed because you feel no pain no trouble while doing any other exercise but the pain is only triggered in several positional exercise only.
I remember when I use to go gym, I feel no pain at all but when ever I do backhand pull ups my shoulder start paining .. and the instructor advised me that this can be healed with some normal muscle relaxing gel and a rest of week or so .. and yes it was gone after a week of rest so you may advise or go for a routine checkup.
