Gym pass in Milan in July

Hi guys,

I will need a gym pass for the first three weeks in Milan. It would be ideal if it were close to Piazza Gaia Aulenti or close to a metro stop downtown anyway.
I am planning to go everyday and work out quite a bit. I have already tried to contact a few gyms in town but I had no luck. If you know of any good gym, could you please give me the name and related costs for a 3-week pass?

Thank you very much!