Is it a one way valve like you see on pool inflation toys and such?
It doesn't really have a valve. It has a hole and a plastic plug that evidently makes a pretty tight seal.
I posted at Amazon, a question for the same or very similar ball I have. Got the answer that gave me the idea/concept I needed:
"you overinflate it a bit then pull the pump out and have plenty of time to plug it as it`s not an air balloon that stretches a lot when pumped and deflates in a jiff. I also believe that there is a valve that slows down deflation for you."
I kinda doubt there's a valve, I think just a hole.
I have the perfect pump for this already. I picked it up 12-15 years ago or so, noticed it at Costco. It's multipurpose, came with attachments, some for basketball etc. balls, one that's conical and looks just like the tips on the pumps that come with the balls. I never used that one before but just did with the ball and it's well inflated now. May even be too inflated, I'll check the balls at my gym and see if they seem as stiff.
In the past I have used that pump to inflate my car's tires (almost nothing else). Does a real good job of it.
The plug in there, white plastic, a little conical, pulls out and air comes out but like that person said, not super fast. You over inflate it some because some air releases between the time you stop inflating and you get the plug back in.