Searching through Deb Wills site, I found the following from a 2004 Dateline Disney Press Release: Notice the last line. Bold emphasis is mine.
Health Clubs Offered to Disney Resort Guests at No Additional Charge
LAKE BUENA VISTA, Fla. -- Joining an ever-growing list of advantages to staying at a Disney resort -- a list which includes early admission to Disney theme parks on certain days and use of the Disney transportation system -- guests staying at certain Walt Disney World Resort hotels now can use health club facilities at no additional charge during their resort stay.
Guests (ages 14 and older) staying at the following resorts can use the health club facilities in their resort at no additional charge (guests ages 17 and younger must be accompanied by a guardian or a parent):
Disney's Animal Kingdom Lodge -- Zahanati Fitness Center
Disney's BoardWalk -- Muscles & Bustles Health Club
Disney's Contemporary Resort -- Olympiad Fitness Center
Disney's Coronado Springs Resort -- LaVida Health Club
Disney's Grand Floridian Resort & Spa -- Disney's Grand Floridian Resort & Spa Health Club
Disney's Old Key West Resort -- R.E.S.T. Exercise Room
Disney's Polynesian Resort -- Disney's Grand Floridian Resort & Spa Health Club
Disney's Saratoga Springs Resort & Spa -- Disney's Saratoga Springs Resort & Spa Fitness Center
Wilderness Lodge and The Villas at Disney's Wilderness Lodge -- Sturdy Branches Fitness Center
Disney's Yacht & Beach Club and Beach Club Villas Resort -- Ship Shape Health Club
Guests not registered to stay in a resort with a health club can still utilize these facilities for a fee.