Harold:
Massage therapy is usually provided without any 'medical devices' that require electrical power, resulting in any article 300 wiring method, dependent on the structure.
The twp I work in has quite a few (10+), and none are Art 517 required.
WE have a 'multi-use' office complex, the Architect has been specifing "ALL HG WIRE" for any of the suites undergoing renovations, irregardless of the tenant usage. His theory is, maybe a 'doctor' will move in.
John