Exercise balls for spheres - inflation valve details needed

I have just discovered this forum and am totally pumped to try a sphere!!! But am confused as to how to reinflate the balls if needed during the process. The exercise ball I have has a funky plug attached to a rod with a barb on the end that goes down into the ball, it's darn near impossible to get that plug out in order to inflate the ball more.....you almost have to deflate the ball to get the plug out by pushing on that barb inside. I don't know if that explaination is clear...kind of hard to explain.

So how is any extra inflation done with concrete covering the ball??? Wonders if some how a regular tire valve could be attached. I saw noknok's thread on spheres showing what looks like the plug I describe and she mentions reinflating but not how to so it.

Anyone have any experience with this???

TIA....Anne aka aartwmich

PS...pic woudn't attach