“Sing from the diaphgram,”  is perhaps the most moronic singing instruction ever taught.

The diaphgram moves on it’s own by reflex.  You do not control it, build it or need to strengthen it. 

Yes, it moves and pushes air out of the lungs.  This is a  REACTION to the vocal requirements. 

Do you control your diaphgram when you just normall breathe?  How about when you talk?  How about when you cough or hiccup or yawn or shout or talk?    Nope, and you should’t worry about controlling the diaphgram when you sing.

So the question becomes, ” how should I control my breathing when I sing.”

Very simply arch your sternum up and forward and breath straight into your upper  chest.  Why?  That is where your lungs are silly.  The belly doesn’t hold any air, breathing to the diaphragm does literlly nothing.  Expand the rib cage and keep the sternum up and the rib cage expanded during all singing and just let the diaphgram naturally do it’s thing. 

Guess what it will do a better job without you trying to control it.

If you need vocal instruction that can really teach you to sing I recommend www.vocalrelease.com  It is the best singing instruction avialable.