Pain in upper right arm

[Frostback2005]

I have been working on getting more wrist cock into my swing and swing down on the ball. The drill I was given was the ball a foot behind the ball you are hitting (and another a few inches inside (towards the body) the ball about a foot back.

I am a 6' 240 pounder who has classic problems associated with that physique. I have the move of dropping the club behind me and swinging hard from the inside. With the new move, I *HAVE* to lift the club up more to *NOT* hit the ball that is about a foot back of the ball I am trying to hit.

So I'm striking the ball a lot better having worked with this drill for a week or two. BUT!!! the muscles in my right upper arm are getting painful. Now it may be that I am using some muscle I have not used before, and it's a matter of building up the muscle...or something else. One thing for sure, when I feel I make a really good swing, I get the pain in the muscle.

This is not rotator cuff stuff, BTW.

Should I work out the muscles there a bit more, or do I need to look at the swing. (Maybe getting the club behind me is getting painful, and I going beyond the limits of my flexibility with a proper swingplane (normally the higher I raise up my hand, the less further I can move my hands behind me).