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Has the "other guy" converted the current page to Google+ Local? If not, you could just "overclaim" it onto Google+ Local, take control of it, and be done with it. Also, for the medical field Google allows doctors/dentists/etc. to have a "personal" business listing, and a "practice" listing, if there's multiple doctors/dentists/etc. at the same practice. This is so people looking for their provider by name can find them, as well as someone searching for the name of the practice. I don't see why fitness (health) would be  any different. If Google doesn't allow practice/personal business listings for fitness, you could create a page with the name of the studio using exact address/phone and then report the current page as a duplicate. Hopefully this helps!! If you aren't sure how to tell if he converted it to G+ Local you can pm me