No Pain, All Gain, Health Club Figures : Exercise: New spa targets affluent people in their 40s and older who do not want punishing workouts--or sweating with younger hard-body members.

The newest comer to Orange County’s health club market is an expensive, exclusive spa that will invite no more than 1,200 people to be members and cost as much as $4,000 to join.

Many lavish new health clubs such as this are built near office towers to help lure tenants. The Spa at the Center, at 695 Town Center Drive, will be no different: C.J. Segerstrom Co. hopes that the spa will attract tenants to the company’s office buildings near South Coast Plaza.

But the spa will aim at a market different from those of most of these clubs: Affluent people in their 40s and older who do not want punishing workouts and may not want to exercise with the younger hard-bodies who frequent many chain clubs.

This spa will issue its members workout togs that look like uniforms so nobody will stand out. And it will have a “less-judgmental” atmosphere than other health clubs, the club’s executive director, Toni Beck, said Thursday at a press conference.

The club plans to charge an initiation fee of $2,500 to $4,000. Monthly fees will range from $130 to $140.

Whether the club can attract 1,200 people willing o pay that much for a club that has no racquetball or basketball courts remains to be seen.

But clearly the investors--a group of private interests; Segerstrom Co., which owns the land, and Prudential Insurance Co.--are betting that they can round up enough affluent middle-age members to make the club go. Leisure Development Interests Inc., a Colorado health club developer, will develop and manage the facility.

At 17,000 square feet, the club is much smaller than two exclusive health clubs near John Wayne Airport: Sports Club Irvine and the Sporting Club, both of which have roughly 100,000 square feet.

The spa will not be competing with these two larger clubs, said Jeffrey G. Jones, president of Leisure Development. Monthly dues at the other two clubs are only slightly less costly, but they cater to young, active customers.

Construction will begin in March, with the club’s opening scheduled in September.

The partners are borrowing hardly any of the $7-million cost of building the spa and are putting up most of the money themselves. New health clubs sometimes run into financial trouble by taking on a lot of debt then signing up too many members to pay the debt. With little debt, this club will not face that problem.