I would venture to guess that you could not deduct health club dues, only because the regs specify that you have to meet certain criteria for a medical, but they don't mandate any particular routine. Also, your employer does not require you to own a membership either.
I honestly tried to deduct haircuts and I couldn't do it. Our SOP's mandate parameters for length of hair, but my accountant said the IRS wouldn't allow something like this.
I checked on this last year. My tax guy said that, too be safe, you should have a letter from an AME stating that you need the health club membership for this reason. That way you have something to fall back on at the audit.