The local health club used to be a mecca for the young and fabulously fit, a place to sweat a bit and then preen to be seen.

But in case you haven't noticed, clubs and gyms have taken on a decidedly grayer tint of late. And it's a trend that's expected to accelerate as aging baby boomers continue to, well, age.

People 55 and older make up the fastest-growing segment of gym and health club members, and they now account for about a quarter of all memberships, according to the International Health, Racquet & Sportsclub Association (IHRSA), the trade association that promotes health clubs.

"In 1987, 1.5 million gym members were 55 and over," said IHRSA spokeswoman Rosemary Lavery. "In 2003, 6.8 million members were 55 and over. In 2004, 10.2 million were 55 and over."

"Obviously, the baby boomers are a big segment of the population," she added. "As they are getting older, they are determined to stay healthy. Working out in the health club is a good preventive."

In other words, the goal today isn't six-pack abs or well-toned thighs, but warding off age-related ailments such as osteoporosis and heart disease while maintaining muscle strength.

To help the resolve of aging members, many health clubs are developing programs designed for middle-aged and older adults. Many are targeted for those who've let their workout routines lapse, as well as those never bitten by the fitness bug. Large chain clubs are doing this, Lavery said, as well as established organizations such as the YMCA.

Curves, for instance, a chain of health clubs worldwide that offers a 30-minute circuit workout, markets its program to women who've probably never belonged to a club. The appeal is that you're surrounded by other novices, many of whom are trying to lose some weight, without the pressure of sharing time and space with the super-fit.

For those who've reached the traditional retirement age of 65, another option is the SilverSneakers Program, offered by about 1,600 fitness centers nationwide. The number of participating clubs has grown dramatically in the past few years, from about 400 in 2002, said Jody Steele, a spokeswoman for Axia Health Management, which administers the program.

"It's a plan we offer to Medicare-eligible persons. Members of various health plans we partner with provide the SilverSneakers program to members," Steele explained.

"We make sure the gyms are senior-friendly," she added. "That means the front desk is friendly and accommodating. Sixty percent of our members have never been in a fitness center before. We train a senior advisor who works at the fitness center who is the liaison for the program."

A typical 45-minute class focuses on exercises that work all major and minor muscle groups, to address strength, flexibility, muscular endurance, balance, coordination, agility, speed and power, Steele said.

Many graduates move on to SilverSneakers II, a class that focuses more on cardiovascular and muscle endurance conditioning. Members also have access to the rest of the health club, as any member with a basic membership would, Steele said.

But boomers who've been sedentary for a while should take a number of steps before joining a program or club, said Fabio Comana, an exercise physiologist at the American Council on Exercise. "If you have been sedentary for six months to a year, consult with your doctor first," he said.

Then, evaluate realistically your fitness level, he added. "Consider what you have been doing recently. If you've been taking walks and engaging in some activity such as gardening, you might be able to adopt a program of moderate exercise."

Then, select a health club or program that meets your goals. For many older Americans, these goals are often maintaining health and quality of life. Also ask about the trainers' qualifications. You should expect them to be certified by one of a number of credible organizations, Comana said, such as the American Council on Exercise, the National Strength and Conditioning Association, the National Council on Strength and Fitness or the National Academy of Sports Medicine.

Seeking testimonials from a contemporary is another good way to tell if a club is a good fit for you, Comana said.