Thank you all for the replies!
@ Robin - I once again agree with you about slow practice. Actually those exrcises make my back and neck feel better
Sleeping, working on computer and being in front of a drawing board all day are the things that make me feel worse.
@ Mat - my docs didnt really say much and didnt point me toward anything specific. My osteo gave me few exercises and they did help get me better but I'm certainly still lacking strength and endurance. Everyone basically said that if I do yoga or martial arts I should talk with advanced teacher to get advise on what kind of strengthening I will need depending on what I will do - hard falls or head stands or whatever else and see what they will advise.
@Walter and David - light resistance does look and sound good! it's is something I've been wanting to research. My osteo got me used to working with various resistance bands and applying it to neck does seem like a good idea!
@& finally at Katherine & Walter - about growing muscles - lol ... I have managed to grow too big many years ago (not in my neck though) and it took me looong time to fix it! That's why I was a bit worried about people suggesting machines and some shoulder and neck strengthening excises with weights.